U.S. patent application number 12/425859 was filed with the patent office on 2009-10-22 for analyzing a stimulation period characteristic for psychiatric disorder therapy delivery.
This patent application is currently assigned to Medtronic, Inc.. Invention is credited to Timothy J. Denison, Jonathon E. Giftakis, Mark T. Rise, Paul H. Stypulkowski.
Application Number | 20090264955 12/425859 |
Document ID | / |
Family ID | 40852200 |
Filed Date | 2009-10-22 |
United States Patent
Application |
20090264955 |
Kind Code |
A1 |
Giftakis; Jonathon E. ; et
al. |
October 22, 2009 |
ANALYZING A STIMULATION PERIOD CHARACTERISTIC FOR PSYCHIATRIC
DISORDER THERAPY DELIVERY
Abstract
A characteristic of a stimulation period, which occurs during
the delivery of stimulation therapy to a patient according to a
therapy program, may be determined based on a physiological
parameter of the patient. The stimulation period characteristic may
include, for example, an amplitude or a trend in a physiological
signal during the stimulation period or a power level or a ratio of
power levels in frequency bands of the physiological signal. In
some embodiments, stimulation period characteristics associated
with a plurality of therapy programs may be used to compare the
programs. In other embodiments, a stimulation period characteristic
may be used to determine a mood state of the patient and, in some
cases, modify a therapy program.
Inventors: |
Giftakis; Jonathon E.;
(Maple Grove, MN) ; Rise; Mark T.; (Monticello,
MN) ; Stypulkowski; Paul H.; (North Oaks, MN)
; Denison; Timothy J.; (Minneapolis, MN) |
Correspondence
Address: |
SHUMAKER & SIEFFERT , P.A
1625 RADIO DRIVE , SUITE 300
WOODBURY
MN
55125
US
|
Assignee: |
Medtronic, Inc.
|
Family ID: |
40852200 |
Appl. No.: |
12/425859 |
Filed: |
April 17, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61046225 |
Apr 18, 2008 |
|
|
|
Current U.S.
Class: |
607/45 |
Current CPC
Class: |
A61N 1/36025 20130101;
G06F 19/00 20130101; A61M 2205/3592 20130101; A61M 5/14276
20130101; A61M 2205/3561 20130101; A61N 1/37211 20130101; A61M
2005/14208 20130101; A61N 1/36082 20130101; A61M 5/1723 20130101;
A61M 2210/0693 20130101; G16H 40/40 20180101; G16H 40/63
20180101 |
Class at
Publication: |
607/45 |
International
Class: |
A61N 1/36 20060101
A61N001/36 |
Claims
1. A method comprising: delivering therapy to a patient according
to a therapy program during a stimulation period, wherein the
therapy program defines a value for at least one therapy parameter
for managing a psychiatric condition of the patient; monitoring a
physiological signal of the patient during the stimulation period,
wherein the physiological signal is indicative of a patient mood
state; automatically determining a characteristic of the
stimulation period based on the monitored physiological signal;
determining a patient mood state based on the characteristic of the
stimulation period; and associating the patient mood state with the
therapy program in a memory.
2. The method of claim 1, wherein the characteristic of the
stimulation period comprises an amplitude of the physiological
signal during the stimulation period, a trend in the physiological
signal during the stimulation period, a power level in a frequency
band of the physiological signal, a ratio of power levels in two or
more frequency bands of the physiological signal during the
stimulation period or a change in the physiological signal relative
to a baseline state during the stimulation period.
3. The method of claim 1, wherein delivering the therapy to the
patient comprises delivering electrical stimulation to a target
tissue site within a brain of the patient.
4. The method of claim 1, wherein monitoring a physiological signal
of the patient comprises monitoring at least one of a brain signal,
heart rate, respiratory rate, electrodermal activity, facial
electromyogram or thermal activity of the patient.
5. The method of claim 1, wherein delivering therapy to the patient
comprises delivering therapy to the patient according to a
plurality of therapy programs, monitoring the physiological signal
of the patient comprises monitoring the physiological signal during
the delivery of therapy according to each of the therapy programs,
and automatically determining the characteristic of the stimulation
period comprises automatically determining the characteristic of
the stimulation period for each therapy program based on a
respective monitored physiological signal, the method further
comprising ordering the plurality of therapy programs based on the
characteristics of the respective stimulation periods.
6. The method of claim 5, wherein the stimulation period
characteristic comprises a first metric, the method further
comprising, for each of the therapy programs: determining a second
metric comprising at least one of an efficacy rating, a mood
indicator, an anxiety indicator, a patient energy level, a mood
improvement rating, side effects rating, a washout period
characteristic or a power usage rating; and determining a composite
metric including the first metric and the second metric.
7. The method of claim 6, wherein determining the composite metric
comprises assigning weights to the first and second metrics.
8. The method of claim 6, wherein ordering the plurality of therapy
programs based on the characteristics of the respective stimulation
periods comprises ordering the plurality of therapy programs based
on the composite metrics.
9. The method of claim 1, wherein determining the patient mood
state based on the characteristic of the stimulation period
comprises comparing the characteristic to a threshold value or
comparing the characteristic to a trend template and determining
the patient mood state based on the comparison, wherein the
threshold value and trend templates are associated with the patient
mood state.
10. The method of claim 1, further comprising modifying the therapy
program value based on the determined patient mood state.
11. The method of claim 1, wherein determining the patient mood
state based on the characteristic of the stimulation period
comprises receiving input from the patient indicative of the
patient mood state, and associating the patient mood state with the
characteristic of the stimulation period in the memory.
12. The method of claim 11, further comprising associating the
characteristic of the stimulation period with a mood state
probability based on the information indicative of the patient mood
state.
13. A system comprising: a memory; a sensor that generates a signal
as a function of at least one physiological parameter indicative of
a mood state of a patient; a medical device that delivers therapy
to the patient according to a therapy program to manage a
psychiatric condition during a stimulation period, wherein the
therapy program defines a value for at least one therapy parameter;
and a processor that monitors the signal during the stimulation
period, automatically determines a characteristic of the
stimulation period based on the signal, determines a patient mood
state based on the characteristic of the stimulation period, and
associates the patient mood state with the therapy program in the
memory.
14. The system of claim 13, further comprising a medical device
programmer, wherein the programmer comprises the processor.
15. The system of claim 13, wherein the medical device comprises
the processor.
16. The system of claim 13, wherein the physiological parameter
comprises at least one of a brain signal, heart rate, respiratory
rate, electrodermal activity, facial electromyogram or thermal
activity of the patient.
17. The system of claim 13, wherein the characteristic of the
stimulation period comprises an amplitude of the physiological
signal during the stimulation period, a trend in the physiological
signal during the stimulation period, a power level in a frequency
band of the physiological signal or a ratio of power levels in two
or more frequency bands of the physiological signal during the
stimulation period.
18. The system of claim 13, wherein the medical device delivers
therapy to the patient according to a plurality of therapy
programs, and for each of the therapy programs, the processor
monitors the physiological parameter of the patient during the
stimulation period and automatically determines the characteristic
of the stimulation period, wherein the processor orders the
plurality of therapy programs based on the characteristics of the
respective stimulation periods.
19. The system of claim 18, wherein the characteristic of the
stimulation period comprises a first metric, and the system further
comprises a user input mechanism, wherein, for each of the therapy
programs, the processor receives a second metric comprising at
least one of an efficacy rating, a mood indicator, an anxiety
indicator, a patient energy level, a mood improvement rating, side
effects rating, or a power usage rating and determines a composite
metric including the first and second metrics.
20. The system of claim 19, wherein the processor receives user
input selecting at least one of the first, second or composite
metrics, and the processor orders the plurality of therapy programs
based on selected metric.
21. The system of claim 13, wherein the processor receives
information indicative of a patient mood state and associates the
patient mood state with the characteristic of the stimulation
period in the memory.
22. The system of claim 13, wherein the processor determines the
patient mood state by at least receiving input from the patient
indicative of the patient mood state, wherein the patient mood
state is associated with the characteristic of the stimulation
period in the memory.
23. A system comprising: a memory; means for delivering therapy to
a patient according to a therapy program during a stimulation
period, wherein the therapy program defines a value for at least
one therapy parameter for managing a psychiatric condition of the
patient; means for monitoring a physiological signal of the patient
during the stimulation period, wherein the physiological signal is
indicative of a patient mood state; means for automatically
determining a characteristic of the stimulation period based on the
monitored physiological signal; means for determining a patient
mood state based on the characteristic of the stimulation period;
and means for associating the patient mood state with the therapy
program in the memory
24. The system of claim 23, wherein the means for delivering
therapy to the patient delivers therapy to the patient according to
a plurality of therapy programs, the means for monitoring the
physiological signal of the patient monitors the physiological
signal during the delivery of therapy according to each of the
therapy programs, and the means for automatically determining the
characteristic of the stimulation period automatically determines
the characteristic of the stimulation period for each therapy
program based on a respective monitored physiological signal, the
system further comprising means for ordering the plurality of
therapy programs based on the characteristics of the respective
stimulation periods.
Description
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/046,225 to Giftakis et al., entitled, "ANALYZING
WASHOUT PERIOD AND STIMULATION PERIOD CHARACTERISTIC FOR
PSYCHIATRIC DISORDER THERAPY DELIVERY" and filed on Apr. 18, 2008,
the entire content of which is incorporated herein by
reference.
TECHNICAL FIELD
[0002] The disclosure relates to medical devices, and, more
particularly, to configuration of therapy parameters.
BACKGROUND
[0003] Implantable medical devices, such as electrical stimulators
or therapeutic agent delivery devices, may be used in different
therapeutic applications, such as deep brain stimulation (DBS),
spinal cord stimulation (SCS), pelvic stimulation, gastric
stimulation, peripheral nerve stimulation, functional electrical
stimulation or delivery of pharmaceutical agent, insulin, pain
relieving agent or anti-inflammatory agent to a target tissue site
within a patient. A medical device may be used to deliver therapy
to a patient to treat a variety of symptoms or patient conditions
such as chronic pain, tremor, Parkinson's disease, other types of
movement disorders, seizure disorders (e.g., epilepsy), urinary or
fecal incontinence, sexual dysfunction, obesity, mood disorders,
gastroparesis or diabetes. In some therapy systems, an implantable
electrical stimulator delivers electrical therapy to a target
tissue site within a patient with the aid of one or more
electrodes, which may be deployed by medical leads. In addition to
or instead of electrical stimulation therapy, a medical device may
deliver a therapeutic agent to a target tissue site within a
patient with the aid of one or more fluid delivery elements, such
as a catheter or a therapeutic agent eluting patch.
[0004] During a programming session, which may occur during implant
of the medical device, during a trial session, or during a
follow-up session after the medical device is implanted in the
patient, a clinician may generate one or more therapy programs that
provide efficacious therapy to the patient, where each therapy
program may define values for a set of therapy parameters. A
medical device may deliver therapy to a patient according to one or
more stored therapy programs. In the case of electrical
stimulation, the therapy parameters may define characteristics of
the electrical stimulation waveform to be delivered. Where
electrical stimulation is delivered in the form of electrical
pulses, for example, the parameters may include an electrode
combination, an amplitude, which may be a current or voltage
amplitude, a pulse width, and a pulse rate for the pulses. In the
case of a therapeutic agent delivery device, the therapy parameters
may include a dose (e.g., a bolus or a group of boluses) size, a
frequency of bolus delivery, a concentration of a therapeutic agent
in the bolus, a type of therapeutic agent to be delivered to the
patient (if the medical device is configured to deliver more than
one type of agent), a lock-out interval, and so forth.
SUMMARY
[0005] In general, the disclosure is directed to devices, systems,
and methods for automatically determining at least one
characteristic of a washout period following delivery of therapy to
a patient. A washout period includes the period of time following
delivery of therapy to a patient during which at least one
carryover effect from the therapy dissipates. In the case of
electrical stimulation therapy, the carryover effect generally
refers to a physiological effect generated in response to the
delivery of an electrical stimulation signal, where the effect
persists after termination of the stimulation signal. Accordingly,
at the end of the washout period, one or more physiological effects
from the delivery of electrical stimulation therapy to the patient
are substantially absent. Carryover effects from delivery of
therapy may be automatically determined based on one or more
physiological parameters of the patient, which may be monitored
during the delivery of therapy and after the cessation of therapy
delivery (e.g., the "post-stimulation" period). The physiological
parameters may include, for example, at least one of a
bioelectrical brain signal (e.g., electroencephalogram or
electrocorticogram), a heart rate, respiratory rate, electrodermal
activity, facial electromyogram or thermal activity of the
patient's body.
[0006] In some embodiments, at least one characteristic of a
washout period is automatically determined for a plurality of
therapy programs based on at least one physiological parameter of
the patient. A therapy program defines respective values for a set
of therapy parameters. In the case of electrical stimulation
therapy, the therapy parameters may include voltage or current
amplitude and frequency of the electrical signals, and, in the case
of electrical pulses, the pulse width, pulse rate, and duty cycle
of the pulses. A signal indicative of the physiological parameter
(i.e., a physiological signal) may be monitored before, during, and
after the delivery of therapy according to a particular therapy
program. In response to the delivery of therapy, the physiological
signal may change. Thus, the change in the signal during the
post-stimulation period may be monitored to determine a
characteristic of the washout period, such as a duration of the
washout period, an amplitude of the physiological signal waveform
during the washout period, a trend in the physiological signal
waveform during the washout period, a power level of the
physiological signal measured in a particular frequency band of the
physiological signal waveform, ratios of power levels between
different frequency bands, and the like.
[0007] The washout period may be useful for timing trials of
different therapy programs. For example, during a trial session in
which therapy is delivered to the patient according to a plurality
of therapy programs to determine an efficacious therapy program or
range of acceptable therapy parameter values, it may be desirable
to deliver test stimulation according to subsequent therapy
programs after the stimulation and at least some carryover effects
of the prior delivered therapy program have substantially
dissipated. The stimulation effects occur while therapy is
delivered. Accordingly, at least one physiological signal of the
patient may be monitored to automatically determine when the
stimulation and carryover effects of the prior delivered therapy
have substantially dissipated, i.e., when the washout period of the
prior delivered therapy has substantially ended.
[0008] In some embodiments, washout periods characteristics, alone
or in addition to other metrics, may be useful for evaluating and
ordering (e.g., ranking) therapy programs. Other metrics for
ordering therapy programs may include the type, severity or
duration of side effects, an efficacy rating, and a power rating,
e.g., the power required for the medical device to generate and
deliver the therapy according to the therapy program.
[0009] The characteristics of at least one physiological signal of
the patient during the washout period may be useful for assessing
the efficacy of a therapy program, and, in some cases, adjusting at
least one parameter value of the therapy program.
[0010] The characteristics of the one or more physiological signals
during the washout period may also be useful for determining a
patient mood state during the washout period. The patient mood
state may be a symptom of a psychiatric disorder with which the
patient is afflicted. For example, a particular waveform trend or
waveform amplitude of the physiological signal may be associated
with a particular patient mood state, such as an anxious state, a
depressive state, and the like. Thus, the monitored signal during
the washout period may be compared to a trend template or amplitude
threshold value to determine the patient mood state. The
probability of the mood state occurring during therapy delivery
based on the therapy program may be determined based on the
determined patient mood state associated with a therapy
program.
[0011] A therapy system for managing a psychiatric disorder of the
patient may be controlled based on a patient mood state that is
determined based on a characteristic of a physiological signal.
Therapy may be delivered to a patient according to a therapy
program, and a physiological parameter of the patient may be
monitored during or after therapy delivery in order to determine a
patient mood state. In some embodiments, the therapy delivery is
stopped prior to determining the patient mood state and the therapy
delivery is restarted upon detecting a negative mood state. In
other embodiments, therapy delivery is delivered until a positive
mood state is detected, at which point the therapy delivery may be
stopped.
[0012] In one embodiment, the disclosure is directed to a method
comprising delivering therapy to a patient according to a therapy
program during a first period, wherein the therapy program defines
a value for at least one therapy parameter for managing a
psychiatric condition (e.g., a psychiatric disorder) of the
patient, monitoring a physiological signal of the patient during a
second period following the first period, and automatically
determining a characteristic of a washout period based on the
monitored physiological signal, wherein the washout period occurs
during the second period, and wherein at least one carryover effect
from the therapy substantially dissipates during the washout
period. The therapy may be electrical stimulation therapy or
delivery of one or more therapeutic agents.
[0013] In another embodiment, the disclosure is directed to a
method comprising delivering therapy to a patient according to a
therapy program during a first period, monitoring a physiological
signal of the patient during a second period following the first
period, receiving information indicative of a patient mood state,
wherein the patient mood state occurs during the second period,
associating the patient mood state with at least one characteristic
of the physiological signal during the second period.
[0014] In another embodiment, the disclosure is directed to a
system comprising a sensor that generates a signal as a function of
at least one physiological parameter of a patient, a medical device
that delivers therapy to a patient according to a therapy program
to manage a psychiatric condition during a first period, wherein
the therapy program defines a value for at least one therapy
parameter, and a processor that monitors the signal during a second
period following the first period, and automatically determines a
characteristic of a washout period for the therapy program based on
the signal, wherein the washout period occurs during the second
period, and wherein at least one carryover effect from the therapy
substantially dissipates during the washout period.
[0015] In another embodiment, the disclosure is directed to a
system comprising means for delivering therapy to a patient
according to a therapy program during a first period, wherein the
therapy program defines a value for at least one therapy parameter
for managing a psychiatric condition of the patient, means for
monitoring a physiological signal of the patient during a second
period following the first period, and means for automatically
determining a characteristic of a washout period based on the
monitored physiological signal, wherein the washout period occurs
during the second period, and wherein at least one carryover effect
from the therapy substantially dissipates during the washout
period.
[0016] In another embodiment, the disclosure is directed to a
method comprising receiving a signal indicative of a physiological
parameter of a patient during a first period during which therapy
according to a first therapy program is delivered to the patient,
detecting a carryover effect from the delivery of the therapy
according to the first therapy program based on the signal, where
the carryover effect occurs during a washout period following the
first period, and automatically initiating delivery of therapy to
the patient according to a second therapy program at a time based
on the washout period.
[0017] In another embodiment, the disclosure is directed to a
method comprising establishing a baseline state of a physiological
signal of a patient, delivering electrical stimulation therapy to a
patient according to a first therapy program during a stimulation
period, monitoring the physiological signal of the patient during a
post-stimulation period following the stimulation period,
automatically determining when the physiological signal returns to
first state that is based on the baseline state, and automatically
delivering electrical stimulation therapy to the patient according
to a second therapy program after the physiological signal returns
to the baseline state.
[0018] In another embodiment, the disclosure is directed to a
system comprising a sensor that generates a signal as a function of
a physiological parameter of a patient, a medical device that
delivers therapy to the patient according to a first therapy
program during a first period, and a processor that receives the
signal from the sensor during a second period following the first
period, detects a carryover effect from delivery of the therapy
according to the first therapy program based on the signal, where
the carryover effect occurs during a washout period during the
second period, and automatically controls the medical device to
deliver therapy to the patient according to a second therapy
program at a time based on the washout period.
[0019] In another embodiment, the disclosure is directed to a
system comprising means for receiving a signal from a sensing
device monitoring a physiological parameter of a patient during a
first period during which therapy according to a first therapy
program is delivered to the patient, means for detecting a
carryover effect from the delivery of the therapy according to the
first therapy program based on the signal, wherein the carryover
effect occurs during a washout period following the first period,
and means for automatically initiating delivery of therapy to the
patient according to a second therapy program at a time based on
the washout period.
[0020] In another embodiment, the disclosure is directed to a
method comprising delivering psychiatric disorder therapy to a
patient via a medical device according to a therapy program,
monitoring a physiological parameter of the patient in response to
the psychiatric disorder therapy, wherein the physiological
parameter comprises at least one of a respiratory rate,
electrodermal activity, thermal activity or muscle activity,
determining a patient mood state based on the physiological
parameter, and controlling the delivery of the psychiatric disorder
therapy based on the determined patient mood state.
[0021] In another embodiment, the disclosure is directed to a
system comprising a medical device that delivers psychiatric
disorder therapy to a patient according to a therapy program, a
sensing module that generates a signal indicative of a
physiological parameter of the patient, wherein the physiological
parameter comprises at least one of a respiratory rate,
electrodermal activity, thermal activity or muscle activity, and a
processor that receives the signal from the sensing module,
determines a patient mood state based on the signal, and controls
the delivery of the psychiatric disorder therapy by the medical
device based on the determined patient mood state.
[0022] In another embodiment, the disclosure is directed to a
system comprising means for delivering psychiatric disorder therapy
to a patient according to a therapy program, means for monitoring a
physiological parameter of the patient in response to the
psychiatric disorder therapy, wherein the physiological parameter
comprises at least one of a respiratory rate, electrodermal
activity or muscle activity, means for determining a patient mood
state based on the physiological parameter, and means for
controlling the means for delivering psychiatric disorder therapy
based on the determined patient mood state.
[0023] In another embodiment, the disclosure is directed to a
method comprising delivering therapy to a patient according to a
therapy program during a stimulation period, wherein the therapy
program defines a value for at least one therapy parameter for
managing a psychiatric condition of the patient, monitoring a
physiological signal of the patient during the stimulation period,
automatically determining a characteristic of the stimulation
period based on the monitored physiological signal, determining a
patient mood state based on the characteristic of the stimulation
period, and associating the patient mood state with the therapy
program in a memory.
[0024] In another embodiment, the disclosure is directed to a
method comprising delivering therapy to a patient according to a
therapy program during a time period, monitoring a physiological
signal of the patient during the time period, receiving information
indicative of a patient mood state, wherein the patient mood state
occurs during the time period, and associating the patient mood
state with at least one characteristic of the physiological signal
during the time.
[0025] In another embodiment, the disclosure is directed to a
system comprising a memory, a sensor that generates a signal as a
function of at least one physiological parameter of a patient, a
medical device that delivers therapy to a patient according to a
therapy program to manage a psychiatric condition during a
stimulation period, wherein the therapy program defines a value for
at least one therapy parameter, and a processor that monitors the
signal during the stimulation period, automatically determines a
characteristic of the stimulation period based on the signal,
determines a patient mood state based on the characteristic of the
stimulation period, and associates the patient mood state with the
therapy program in the memory.
[0026] In another embodiment, the disclosure is directed to a
system comprising a memory, means for delivering therapy to a
patient according to a therapy program during a stimulation period,
wherein the therapy program defines a value for at least one
therapy parameter for managing a psychiatric condition of the
patient, means for monitoring a physiological signal of the patient
during the stimulation period, means for automatically determining
a characteristic of the stimulation period based on the monitored
physiological signal, means for determining a patient mood state
based on the characteristic of the stimulation period, and means
for associating the patient mood state with the therapy program in
the memory.
[0027] In another embodiment, the disclosure is directed to a
method comprising delivering psychiatric disorder therapy to a
patient via a medical device according to a therapy program,
monitoring a physiological parameter of the patient in response to
the psychiatric disorder therapy according to the therapy program,
determining a first patient mood state based on the physiological
parameter, receiving input indicating a second mood state
experienced by the patient in response to the delivery of the
psychiatric disorder therapy according to the therapy program,
determining whether the first and second mood states are consistent
to generate a consistency determination, and associating the
consistency determination with the therapy program.
[0028] In another embodiment, the disclosure is directed to a
system comprising a medical device that delivers psychiatric
disorder therapy to a patient according to a therapy program, a
sensing module that generates a signal indicative of a
physiological parameter of the patient, and a processor that
receives the signal from the sensing module, determines a first
patient mood state based on the signal, receives input indicating a
second mood state experienced by the patient in response to the
delivery of the psychiatric disorder therapy according to the
therapy program, determines whether the first and second mood
states are consistent to generate a consistency determination, and
associates the consistency determination with the therapy
program.
[0029] In another aspect, the disclosure is directed to a
computer-readable medium comprising instructions. The instructions
cause a programmable processor to perform any part of the
techniques described herein. The instructions may be, for example,
software instructions, such as those used to define a software or
computer program. The computer-readable medium may be a
computer-readable storage medium such as a storage device (e.g., a
disk drive, or an optical drive), memory (e.g., a Flash memory,
random access memory or RAM) or any other type of volatile or
non-volatile memory that stores instructions (e.g., in the form of
a computer program or other executable) to cause a programmable
processor to perform the techniques described herein.
[0030] The details of one or more examples are set forth in the
accompanying drawings and the description below. Other features,
objects, and advantages of the invention will be apparent from the
description and drawings, and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is a conceptual diagram illustrating an example
embodiment of a therapy system including an implantable medical
device, a patient programmer, and a clinician programmer.
[0032] FIG. 2 is a schematic block diagram illustrating example
components of the implantable medical device of FIG. 1.
[0033] FIG. 3 is a schematic block diagram illustrating example
components of the patient programmer of FIG. 1.
[0034] FIG. 4 is a schematic block diagram illustrating example
components of the clinician programmer of FIG. 1.
[0035] FIGS. 5A-5E are schematic diagrams of physiological signal
waveforms prior to, during, and after delivery of electrical
stimulation signals by a medical device.
[0036] FIG. 6 is a schematic diagram illustrating example external
sensing devices that may be used to monitor a physiological
parameter of a patient.
[0037] FIGS. 7A-7C are flow diagrams illustrating example
techniques for timing delivery of therapy according to different
therapy programs during a programming session.
[0038] FIG. 8 is a flow diagram illustrating a technique for
automatically determining a characteristic of a washout period
following therapy delivery according to a therapy program and
associating the washout period characteristic with the therapy
program.
[0039] FIG. 9 is a schematic illustration of a clinician
programmer, which includes a display presenting a graphical user
interface (GUI) with a list of therapy programs.
[0040] FIG. 10 is a flow diagram illustrating an example technique
for ordering therapy programs based on a washout period
characteristic.
[0041] FIG. 11 is a flow diagram illustrating an example technique
for associating different patient mood states with one or more
washout period characteristics.
[0042] FIG. 12 is a flow diagram illustrating an example technique
for associating a therapy program with a patient state based on a
comparison between a washout period characteristic and a threshold
value.
[0043] FIG. 13 is an example data structure that associates
different patient mood states with threshold values.
[0044] FIG. 14 is a flow diagram illustrating an example technique
for associating a therapy program with a patient state based on a
comparison between a washout period characteristic and a
template.
[0045] FIG. 15 is a flow diagram illustrating an example technique
for associating a therapy program with a patient state based on a
comparison between a washout period characteristic and a threshold
energy level of a frequency band.
[0046] FIG. 16 is a flow diagram illustrating an example technique
for adjusting a therapy program based on a patient mood state.
[0047] FIGS. 17 and 18 are flow diagrams illustrating example
techniques for controlling the delivery of therapy based on a
patient mood state.
[0048] FIG. 19 is a conceptual diagram illustrating the
relationship between a physiological signal and stimulation
signals.
[0049] FIG. 20 is a flow diagram illustrating an example technique
for determining whether patient input indicating a mood state and a
mood state determined based on a physiological signal are
consistent.
DETAILED DESCRIPTION
[0050] FIG. 1 is a conceptual diagram illustrating an embodiment of
a therapy system 10 that is implanted proximate to brain 12 of
patient 14 in order to help manage a patient condition, such as a
psychiatric disorder. Examples of psychiatric disorders that
therapy system 10 may be useful for managing include major
depressive disorder (MDD), bipolar disorder, anxiety disorders,
post traumatic stress disorder, dysthymic disorder, and
obsessive-compulsive disorder (OCD). While patient 14 is generally
referred to as a human patient, other mammalian or non-mammalian
patients are also contemplated. Therapy system 10 includes
implantable medical device (IMD) 16, connector block 17, lead
extension 18, leads 20A and 20B, clinician programmer 22, patient
programmer 24, and sensing module 26 (also referred to as "sensor
26"). IMD 16 includes a therapy module that delivers electrical
stimulation therapy to one or more regions of brain 12 via leads
20A and 20B (collectively referred to as "leads 20"). In the
embodiment shown in FIG. 1, therapy system 10 may be referred to a
deep brain stimulation (DBS) system because IMD 16 provides
electrical stimulation therapy directly tissue within brain 12,
e.g., a tissue site under the dura mater of brain 12. In other
embodiments, leads 20 may be positioned to deliver therapy to a
surface of brain 12 (e.g., the cortical surface of brain 12).
[0051] In the embodiment shown in FIG. 1, IMD 16 may be implanted
within a chest cavity of patient 14. In other embodiments, IMD 16
may be implanted within other regions of patient 14, such as a
subcutaneous pocket in the abdomen of patient 14 or proximate the
cranium of patient 14. Implanted lead extension 18 is coupled to
IMD 16 via connector block 17, which may include, for example,
electrical contacts that electrically couple to respective
electrical contacts on lead extension 18. The electrical contacts
electrically couple the electrodes carried by leads 20 to IMD 16.
Lead extension 18 traverses from the implant site of IMD 16 within
a chest cavity of patient 14, along the neck of patient 14 and
through the cranium of patient 14 to access brain 12.
[0052] Leads 20 are implanted within the right and left
hemispheres, respectively, of brain 12 in order deliver electrical
stimulation to one or more regions of brain 12, which may be
selected based on many factors, such as the type of patient
condition for which therapy system 10 is implemented to manage.
Different neurological or psychiatric disorders may be associated
with activity in one or more of regions of brain 12, which may
differ between patients. For example, in the case of MDD, bipolar
disorder, OCD, or other anxiety disorders, leads 20 may be
implanted to deliver electrical stimulation to the anterior limb of
the internal capsule of brain 12, and only the ventral portion of
the anterior limb of the internal capsule (also referred to as a
VC/VS), the subgenual component of the cingulate cortex, anterior
cingulate cortex Brodmann areas 32 and 24, various parts of the
prefrontal cortex, including the dorsal lateral and medial
pre-frontal cortex (PFC) (e.g., Brodmann area 9), ventromedial
prefrontal cortex (e.g., Brodmann area 10), the lateral and medial
orbitofrontal cortex (e.g., Brodmann area 11), the medial or
nucleus accumbens, thalamus, intralaminar thalamic nuclei,
amygdala, hippocampus, the lateral hypothalamus, the Locus
ceruleus, the dorsal raphe nucleus, ventral tegmentum, the
substantia nigra, subthalamic nucleus, the inferior thalamic
peduncle, the dorsal medial nucleus of the thalamus, the habenula,
or any combination thereof.
[0053] Although leads 20 are shown in FIG. 1 as being coupled to a
common lead extension 18, in other embodiments, leads 20 may be
coupled to IMD 16 via separate lead extensions or directly coupled
to IMD 16. Leads 20 may deliver electrical stimulation to treat any
number of neurological disorders or diseases in addition to
psychiatric disorders, such as movement disorders or seizure
disorders. Examples of movement disorders include a reduction in
muscle control, motion impairment or other movement problems, such
as rigidity, bradykinesia, rhythmic hyperkinesia, nonrhythmic
hyperkinesia, dystonia, tremor, and akinesia. Movement disorders
may be associated with patient disease states, such as Parkinson's
disease or Huntington's disease. An example seizure disorder
includes epilepsy.
[0054] Leads 20 may be implanted within a desired location of brain
12 via any suitable technique, such as through respective burr
holes in a skull of patient 14 or through a common burr hole in the
cranium. Leads 20 may be placed at any location within brain 12
such that the electrodes of the leads are capable of providing
electrical stimulation to targeted tissue during treatment.
Electrical stimulation generated from the signal generator (not
shown) within the therapy module of IMD 16 may help prevent the
onset of events associated with the patient's psychiatric disorder
or mitigate symptoms of the psychiatric disorder. For example,
electrical stimulation therapy delivered by IMD 16 to a target
tissue site within brain 12 may help prevent a manic event if
patient 14 has a bipolar disorder or help patient 14 maintain a
mood state between a manic state and a depressive state. The exact
therapy parameter values of the stimulation therapy, such as the
amplitude or magnitude of the stimulation signals, the duration of
each signal, the waveform of the stimuli (e.g., rectangular,
sinusoidal or ramped signals), the frequency of the signals, and
the like, may be specific for the particular target stimulation
site (e.g., the region of the brain) involved as well as the
particular patient and patient condition.
[0055] In the case of stimulation pulses, the stimulation therapy
may be characterized by selected pulse parameters, such as pulse
amplitude, pulse rate, and pulse width. In addition, if different
electrodes are available for delivery of stimulation, the therapy
may be further characterized by different electrode combinations,
which can include selected electrodes and their respective
polarities. Known techniques for determining the optimal
stimulation parameters may be employed. In one embodiment,
electrodes of leads 20 are positioned to deliver stimulation
therapy to an anterior limb of the internal capsule of brain 12 in
order to manage symptoms of a MDD of patient 14, and stimulation
therapy is delivered via a selected combination of the electrodes
to the anterior limb of the internal capsule with electrical
stimulation including a frequency of about 2 hertz (Hz) to about
2000 Hz, a voltage amplitude of about 0.5 volts (V) to about 50 V,
and a pulse width of about 60 microseconds (.mu.s) to about 4
milliseconds (ms). However, other embodiments may implement
stimulation therapy including other stimulation parameters.
[0056] The electrodes of leads 20 are shown as ring electrodes.
Ring electrodes may be relatively easy to program and are typically
capable of delivering an electrical field to any tissue adjacent to
leads 20. In other embodiments, the electrodes of leads 20 may have
different configurations. For example, the electrodes of leads 20
may have a complex electrode array geometry that is capable of
producing shaped electrical fields. The complex electrode array
geometry may include multiple electrodes (e.g., partial ring or
segmented electrodes) around the perimeter of each lead 20, rather
than a ring electrode. In this manner, electrical stimulation may
be directed to a specific direction from leads 20 to enhance
therapy efficacy and reduce possible adverse side effects from
stimulating a large volume of tissue. In some embodiments, a
housing of IMD 16 may include one or more stimulation and/or
sensing electrodes. In alternative examples, leads 20 may have
shapes other than elongated cylinders as shown in FIG. 1. For
example, leads 20 may be paddle leads, spherical leads, bendable
leads, or any other type of shape effective in treating patient
14.
[0057] In some embodiments, leads 20 may include sensing electrodes
positioned to detect electrical signals (also referred to as
bioelectrical brain signals) within one or more region of patient's
brain 12. Alternatively, another set of sensing electrodes may
monitor the electrical signal. The monitored electrical signals may
include an electroencephalogram (EEG) signal. Electrodes implanted
closer to the target region of brain 12 may help generate an EEG
signal that provides more useful information than an EEG generated
via a surface electrode array because of the proximity to brain 12.
The EEG signal that is generated from implanted electrode array may
also be referred to as an electrocorticography (ECoG) signal. In
some embodiments, the electrical signals from within brain 12 may
be used to determine a characteristic of a washout period, as
described below with respect to FIG. 8. In other embodiments, an
EEG signal of patient 14 may be monitored with external electrodes,
e.g., scalp electrodes.
[0058] In some embodiments, the electrical signals from within
brain 12 may be used to determine at least one characteristic of a
washout period following delivery of therapy to a patient according
to a therapy program. A washout period is the period of time
following delivery of therapy to patient 14 during which one or
more carryover effects from the therapy delivery substantially
dissipates. In the case of electrical stimulation therapy, the
carryover effect generally refers to a physiological effect from
delivery of electrical stimulation signals that persist after
termination of the signals. The end of the washout period
associated with a therapy program may be the time at which at least
one of the physiological effects resulting from the delivery of
electrical stimulation therapy to patient 14 according to the
therapy program have substantially dissipated, such that patient 14
returns to a baseline condition. The baseline condition may be, for
example, the mood state or state of a physiological parameter prior
to delivery of therapy according to the therapy program, or prior
to the delivery of any therapy to patient 14.
[0059] One type of characteristic of the washout period may include
the duration of the washout period, i.e., the time it takes for a
physiological signal to return to a particular state, which may be
a baseline state. The baseline state may be characterized by a
range of amplitude values or a waveform and may be based on the
state of patient 14 prior to delivery of stimulation according to a
particular therapy program or prior to any therapy delivery. Other
characteristics of the washout period may include the greatest or
smallest amplitude of the physiological signal during the washout
period, the average or median value of the physiological signal
amplitude during the washout period, a trend in the physiological
signal waveform during the washout period (e.g., a rate of change
over time), a power level of the physiological signal measured in a
particular frequency band of the physiological signal waveform
during the washout period, ratios of power levels between different
frequency bands during the washout period, and the like.
[0060] A carryover effect during the washout period may be detected
by monitoring one or more physiological signals of patient 14 in
addition to or instead of the EEG (or ECoG) signal. In embodiments
in which therapy system 10 is used to manage a psychiatric disorder
of patient 14, the physiological signals that are monitored may be
indicative of the patient's mood state, although not necessarily
symptomatic of the patient's mood disorder. In this way,
characteristics of the physiological signal during the washout
period may be a surrogate marker for a patient mood state. In
different embodiments, suitable physiological signals for detecting
a carryover effect and determining a characteristic of a washout
period may include, but are not limited to, signals indicative of a
bioelectrical brain signal (e.g., an EEG or ECoG), heart rate,
respiratory rate, electrodermal activity (e.g., skin conductance
level or galvanic skin response), muscle activity (e.g., via EMG),
thermal sensing (e.g. to detect facial flushing), or cardiac Q-T
interval.
[0061] Brain activity may be indicated by, for example, monitoring
electrical signals of the brain, such as EEG or ECoG signals. The
heart rate and respiratory rate may be determined by measuring the
heart rate and respiratory rate at any suitable place on the
patient's body, and need not be directly measured from the heart or
lungs. The electrodermal and thermal activity of patient 14 may be
measured at the patient's face or any other suitable place on the
patient's body, such as on the patient's hands (e.g., the palms),
arms, legs, torso, neck, and the like. Thermal activity may
indicate, for example, the temperature of the patient's skin due to
skin flushing or an increase in blood flow in the region of the
patient's skin. Monitoring the patient's muscle activity may detect
changes to the patient's demeanor, such as changes to the patient's
facial features (e.g., by detect facial contraction), tensing of
the patient's neck and should muscles, clenching of the patient's
hands, and the like. Such muscle movement may be detected via an
EMG sensor.
[0062] A cardiac Q-T interval is a measure of the time between the
start of the Q wave of the heart's electrical cycle and the end of
the T wave, and is typically dependent upon the heart rate.
Respiratory rate, heart rate, electrodermal activity, facial
flushing, and cardiac Q-T interval signals may each be indicative
of the patient's anxiety level. For example, a relatively high
respiratory rate, heart rate, electrodermal activity, facial
flushing, and Q-T interval may be indicative of a relatively high
anxiety level of patient 14.
[0063] A decrease in the patient's anxiety level during a washout
period may be desirable in situations in which therapy system 10 is
used to provide therapy to manage an anxiety disorder or OCD. On
the other hand, an increase in the patient's anxiety level during
the washout period may be desirable in situations in which therapy
system 10 is used to provide therapy to manage MDD. As described in
further detail below, a therapy program may be selected such that
the patient's heart rate or respiratory rate remains within a
particular range in order to reduce or minimize the possibility of
interfering with the patient's normal function or in order to
reduce or minimize the possibility of causing patient 14 to achieve
an abnormal emotional arousal state, such as elation, hypomania or
mania.
[0064] Sensing module 26 is configured to monitor a physiological
signal of patient 14 to detect a stimulation and/or carryover
effect from therapy delivery and to determine a washout period
characteristic for a particular therapy program. Sensing module 26
may be external to patient 14, may be implanted within patient 14
or may include portions both implanted and external to patient 14.
In some embodiments, sensing module 26 may be incorporated in a
common housing with IMD 16, may include electrodes on an outer
housing of IMD 16 or may be coupled to IMD 16 via leads 20 or
separate leads. Sensing module 26 is shown schematically in FIG.
1.
[0065] As described below with reference to FIG. 6, in some
embodiments, sensing module 26 includes electrodes positioned on
the patient's face in order to detect the electrical potential
generated by the patient's facial muscle cells when the patient's
face contracts. That is, in some embodiments, sensing module 26 may
include one or more electrodes positioned to detect EMG signals,
which may indicate changes to the patient's facial expressions.
Certain EMG signals may be associated with particular facial
expressions, e.g., during a learning process. In some embodiments,
sensing module 26 may include one or more thermal sensing
electrodes positioned on the patient's face in order to detect
facial flushing, and/or one or more sensing electrodes to detect
electrodermal activity, which may indicate changes in conductivity
of the patient's skin (e.g., attributable to perspiration). In
addition to or instead of the EMG or thermal sensing electrodes,
sensing module 26 may include a respiration belt or an
electrocardiogram (ECG) belt, as described below with reference to
FIG. 6.
[0066] If sensing module 26 determines one or more physiological
parameters of patient 14 within brain 12, sensing module 26 and IMD
16 may deliver and sense therapy to the same or different target
tissue sites. For example, in one embodiment, sensing module 26 may
detect an EEG signal within the CG25 of brain 12, while IMD 16
delivers therapy to the VC/VS. The CG25 of brain 12 may also be
referred to as the subgenual cingulate. As another example, sensing
module 26 may detect an EEG signal within the VC/VS of brain 12,
while IMD 16 delivers therapy to the CG25. As another example, both
IMD 16 and sensing module 26 may be configured to deliver therapy
and sense, respectively, within the VC/VS of brain 12. In other
cases, both IMD 16 and sensing module 26 may be configured to
deliver therapy and sense, respectively, within the CG25 of brain
12.
[0067] IMD 16 includes a therapy module that generates the
electrical stimulation delivered to patient 14 via leads 20. In the
embodiment shown in FIG. 1, IMD 16 generates the electrical
stimulation according to one or more therapy parameters, which may
be arranged in a therapy program (or a parameter set). In
particular, a signal generator (not shown) within IMD 16 produces
the stimulation in the manner defined by the therapy program or
group of programs selected by the clinician and/or patient 14. The
signal generator may be configured to produce electrical pulses to
treat patient 14. In other embodiments, the signal generator of IMD
16 may be configured to generate a continuous wave signal, e.g., a
sine wave or triangle wave. In either case, IMD 16 generates the
electrical stimulation therapy for DBS according to therapy
parameter values defined by a particular therapy program.
[0068] A therapy program defines respective values for a number of
parameters that define the stimulation. For example, the therapy
parameters may include voltage or current pulse amplitudes, pulse
widths, pulse rates, pulse frequencies, electrode combinations, and
the like. IMD 16 may store a plurality of programs. In some cases,
the one or more stimulation programs are organized into groups, and
IMD 16 may deliver stimulation to patient 14 according to a program
group. During a trial stage in which IMD 16 is evaluated to
determine whether IMD 16 provides efficacious therapy to patient
14, the stored programs may be tested and evaluated for
efficacy.
[0069] IMD 16 may include a memory to store one or more therapy
programs (e.g., arranged in groups), and instructions defining the
extent to which patient 14 may adjust therapy parameters, switch
between programs, or undertake other therapy adjustments. Patient
14 may generate additional programs for use by IMD 16 via patient
programmer 24 at any time during therapy or as designated by the
clinician.
[0070] Generally, an outer housing of IMD 16 is constructed of a
biocompatible material that resists corrosion and degradation from
bodily fluids. IMD 16 may be implanted within a subcutaneous pocket
close to the stimulation site. Although IMD 16 is implanted within
a chest cavity of patient 14 in the embodiment shown in FIG. 1, in
other embodiments, IMD 16 may be implanted within cranium. In
addition, while IMD 16 is shown as implanted within patient 14 in
FIG. 1, in other embodiments, IMD 16 may be located external to the
patient. For example, IMD 16 may be a trial stimulator electrically
coupled to leads 20 via a percutaneous lead during a trial period.
If the trial stimulator indicates therapy system 10 provides
effective treatment to patient 14, the clinician may implant a
chronic stimulator within patient 14 for long term treatment.
[0071] Clinician programmer 22 may be a computing device including,
for example, a personal digital assistant (PDA), a laptop computer,
a desktop PC, a workstation, and the like that permits a clinician
to program electrical stimulation therapy for patient 14, e.g.,
using input keys and a display. For example, using clinician
programmer 22, the clinician may specify therapy programs that
include one or more therapy parameters and/or organize the therapy
programs into therapy program groups (i.e., groups including one or
more therapy parameters) for use in delivery of DBS. Clinician
programmer 22 supports telemetry (e.g., radio frequency (RF)
telemetry) with IMD 16 to download stimulation parameters and,
optionally, upload operational or physiological data stored by IMD
16. In this manner, the clinician may periodically interrogate IMD
16 to evaluate efficacy and, if necessary, modify the stimulation
parameters.
[0072] Like clinician programmer 22, patient programmer 24 may be a
handheld computing device. Patient programmer 24 may also include a
display and input keys to allow patient 14 to interact with patient
programmer 24 and IMD 16. In this manner, patient programmer 24
provides patient 14 with an interface for limited control of
electrical stimulation therapy provided by IMD 16. For example,
patient 14 may use patient programmer 24 to start, stop or adjust
electrical stimulation therapy. In particular, patient programmer
24 may permit patient 14 to adjust stimulation parameters such as
duration, amplitude, pulse width and pulse rate within an
adjustment range specified by the clinician via clinician
programmer 22, select from a library of stored stimulation therapy
programs, or reset the current therapy cycle.
[0073] Patient programmer 24 includes input mechanisms to allow
patient 14 to enter information related to a patient event or
information in response to the delivery of therapy according to a
particular therapy program. For example, any of the above-listed
input mechanisms may be used to enter information including, but
not limited to, information characterizing the patient mood during
a washout period following delivery of therapy to patient 14
according to a specific therapy program. The information entered by
patient 14 may be associated with the specific therapy program.
[0074] Clinician programmer 22 may be used to program and/or
interrogate IMD 16 and patient programmer 24, as described in
further detail below. IMD 16, clinician programmer 22, and patient
programmer 24 may communicate via cables or a wireless
communication, as shown in FIG. 1. Clinician programmer 22 and
patient programmer 24 may, for example, communicate via wireless
communication with IMD 16 using RF telemetry techniques known in
the art. Clinician programmer 22 and patient programmer 24 also may
communicate with each other using any of a variety of local
wireless communication techniques, such as RF communication
according to the 802.11 or Bluetooth specification sets, infrared
communication, e.g., according to the IrDA standard, or other
standard or proprietary telemetry protocols.
[0075] Although IMD 16 configured to deliver electrical stimulation
is illustrated in the embodiment shown in FIG. 1, in other
embodiments, therapy system 10 may include a medical device
configured to deliver a therapeutic agent in addition to or instead
of IMD 16. The therapeutic agent may be used to provide therapy to
patient 14 to manage a psychiatric disorder of patient 14, and may
be delivered to the patient's brain 12, blood stream or tissue. In
some embodiments, the medical device that delivers the therapeutic
agent is implanted within patient 14, while in other embodiments,
the medical device is external to patient 14. For example, the
medical device may be an implanted or external drug pump that
delivers a therapeutic agent to a target tissue site within patient
14 with the aid of one or more catheters. As another example, the
medical device may be an external patch that is worn on a skin
surface of patient 14, where the patch elutes a therapeutic agent,
which is then absorbed by the patient's skin. Other types of
therapeutic agent delivery systems are contemplated.
[0076] FIG. 2 is a functional block diagram illustrating components
of an embodiment of IMD 16 in greater detail. IMD 16 is coupled to
leads 20A and 20B, which include electrodes 30A-30D and 31A-30D,
respectively. Although IMD 16 is coupled directly to leads 20, in
other embodiments, IMD 16 may be coupled to leads 20 indirectly,
e.g., via lead extension 18 (FIG. 1). In the example shown in FIG.
2, IMD 16 includes therapy module 32, processor 34, memory 35,
power source 36, and telemetry module 38.
[0077] IMD 16 may deliver electrical stimulation therapy to brain
12 of patient 14 via electrodes 30A-30D of lead 20A and electrodes
31A-30D of lead 20B (collectively "electrodes 30 and 31"). In the
embodiment shown in FIG. 2, implantable medical leads 20 are
substantially cylindrical, such that electrodes 30, 31 are
positioned on a rounded outer surface of leads 20. As previously
described, in other embodiments, leads 20 may be, at least in part,
paddle-shaped (i.e., a "paddle" lead). In some embodiments,
electrodes 30, 31 may be ring electrodes. In other embodiments,
electrodes 30, 31 may be segmented or partial ring electrodes, each
of which extends along an arc less than 360 degrees (e.g., 90-120
degrees) around the outer perimeter of the respective lead 20. The
use of segmented or partial ring electrodes 30, 31 may also reduce
the overall power delivered to electrodes 30, 31 by IMD 16 because
of the ability to more efficiently deliver stimulation to a target
stimulation site by eliminating or minimizing the delivery of
stimulation to unwanted or unnecessary regions within patient
16.
[0078] The configuration, type, and number of electrodes 30, 31
illustrated in FIG. 2 are merely exemplary. For example, IMD 16 may
be coupled to one lead with eight electrodes on the lead or three
or more leads with the aid of bifurcated lead extensions.
Electrodes 30, 31 are electrically coupled to a therapy module 32
of IMD 16 via conductors within the respective leads 20A, 20B. Each
of electrodes 30, 31 may be coupled to separate conductors so that
electrodes 30, 31 may be individually selected, or in some
embodiments, two or more electrodes 30 and/or two or more
electrodes 31 may be coupled to a common conductor. In one
embodiment, an implantable signal generator or other stimulation
circuitry within therapy module 32 delivers electrical signals
(e.g., pulses or substantially continuous-time signals, such as
sinusoidal signals) to a target tissue site within patient 14 via
at least some of electrodes 30, 31 under the control of processor
34. The stimulation energy generated by therapy module 32 may be
delivered from therapy module 32 to selected electrodes 30, 31 via
a switching module and conductors carried by leads 16, as
controlled by processor 34.
[0079] Processor 34 may include any one or more of a
microprocessor, a controller, a digital signal processor (DSP), an
application specific integrated circuit (ASIC), a field
programmable gate array (FPGA), discrete logic circuitry, or the
like. The functions attributed to processors described herein may
be embodied in a hardware device via software, firmware, hardware
or any combination thereof. Processor 34 controls the implantable
signal generator within therapy module 32 to deliver electrical
stimulation therapy according to selected therapy parameters.
Specifically, processor 34 controls therapy module 32 to deliver
electrical signals with selected voltage or current amplitudes,
pulse widths (if applicable), and rates specified by one or more
therapy programs, which may be arranged into therapy program
groups. In one embodiment, processor 34 controls therapy module 32
to deliver stimulation therapy according to one therapy program
group at a time. The therapy programs may be stored within memory
35. In another embodiment, therapy programs are stored within at
least one of clinician programmer 22 or patient programmer 24,
which transmits the therapy programs to IMD 16 via telemetry module
38.
[0080] In addition, processor 34 may also control therapy module 32
to deliver the electrical stimulation signals via selected subsets
of electrodes 30, 31 with selected polarities. For example,
electrodes 30, 31 may be combined in various bipolar or multi-polar
combinations to deliver stimulation energy to selected sites, such
as sites within brain 12. The above-mentioned switch matrix may be
controlled by processor 34 to configure electrodes 30, 31 in
accordance with a therapy program.
[0081] In embodiments in which IMD 16 senses a patient parameter,
such as an EEG, ECoG, heart rate or respiratory rate of patient 14,
processor 34 may control therapy module 32 to sense the patient
parameter. The sensed parameter signals generated by therapy module
32 may be stored within memory 35. Memory 35 may include any
volatile, non-volatile, magnetic, optical, or electrical media,
such as a random access memory (RAM), read-only memory (ROM),
non-volatile RAM (NVRAM), electrically-erasable programmable ROM
(EEPROM), flash memory, and the like. Memory 35 may store program
instructions that, when executed by processor 34, cause IMD 16 to
perform the functions ascribed to IMD 16 herein. In some
embodiments, memory 35 may also store the parameters for therapy
programs or program groups and/or patient physiological data (such
as sensed physiological signals) obtained by IMD 16 or another
sensing device.
[0082] During a trial session, which may occur after implantation
of IMD 16 or prior to implantation of IMD 16, a clinician may
determine the therapy parameter values that provide efficacious
therapy to patient 14. Processor 34 may control therapy module 32
based on information provided by clinician programmer 22, patient
programmer 24 or another computing device. For example, the
clinician may interact with clinician programmer 22 to select a
particular therapy program and clinician programmer 22 may transmit
a control signal to IMD 16, which is received by telemetry module
38 of IMD 16. The control signal may cause processor 34 to control
therapy module 32 to deliver therapy based on the parameter values
specific by the clinician-selected therapy program. As another
example, clinician programmer 22, patient programmer 24 or another
computing device may utilize a search algorithm that automatically
selects therapy programs for trialing, i.e., testing on patient 14.
When a therapy program is trialed, therapy is delivered to patient
14 according to the therapy program for a predetermined amount of
time, which may be a few minutes to a few hours or days, in order
to assess the efficacy of the therapy program in managing the
patient's condition. The efficacy of the therapy program may be
analyzed in terms of the therapeutic benefits to patient 14, as
well as the existence of side effects, which may include the
presence, severity, and duration of the side effects.
[0083] FIG. 3 is a functional block diagram illustrating components
of an example patient programmer 24, which includes processor 40,
memory 42, user interface 44, telemetry module 46, and power source
48. Processor 40 controls user interface 44 and telemetry module
46, and stores and retrieves information and instructions to and
from memory 42. Patient programmer 24 may be a dedicated hardware
device with dedicated software for programming of IMD 16.
Alternatively, patient programmer 24 may be an off-the-shelf
computing device running an application that enables programmer 24
to program IMD 16.
[0084] Patient 14 may use patient programmer 24 to select therapy
programs (e.g., sets of stimulation parameter values), generate new
therapy programs, modify therapy programs through individual or
global adjustments or transmit the new programs to a medical
device, such as IMD 16 (FIGS. 1 and 2). Patient 14 may interact
with patient programmer 24 via user interface 44, which includes
user input mechanism 56 and display 60. Patient 14 may input
information via user interface 44 relating to the therapeutic
efficacy of a therapy program or a mood state during a washout
period following therapy delivery by IMD 16 according to a
particular therapy program.
[0085] User input mechanism 56 may include any suitable mechanism
for receiving input from patient 14 or another user. In one
embodiment, user input mechanism includes an alphanumeric keypad.
In another embodiment, user input mechanism 56 includes a limited
set of buttons that are not necessarily associated with
alphanumeric indicators. For example, the limited set of buttons
may include directional buttons that permit patient 14 to scroll
up, down, or sideways through a display presented on display 60,
select items shown on display 60, as well as enter information. The
limited set of buttons may also include "increment/decrement"
buttons in order to increase or decrease a stimulation frequency or
amplitude of stimulation delivered by IMD 16.
[0086] User input mechanism 56 may include any one or more of push
buttons, soft-keys (e.g., with functions and contexts indicated on
display 60), voice activated commands, mechanisms activated by
physical interactions, magnetically triggered mechanisms,
mechanisms activated upon password authentication push buttons,
contacts defined by a touch screen, or any other suitable user
interface. In some embodiments, buttons of user input mechanism 56
may be reprogrammable. That is, during the course of use of patient
programmer 24, the buttons of user input mechanism 56 may be
reprogrammed to provide different programming functionalities as
the needs of patient 14 change or if the type of IMD 16 implanted
within patient 14 changes. User input mechanism 56 may be
reprogrammed, for example, by clinician programmer 22 (FIG. 1) or
another computing device.
[0087] Display 60 may include a color or monochrome display screen,
such as a liquid crystal display (LCD), light emitting diode (LED)
display or any other suitable type of display. Patient programmer
24 may present information related to stimulation therapy provided
by IMD 16, as well as other information, such as historical data
regarding the patient's condition and past event information.
Processor 40 monitors activity from user input mechanism 56, and
controls display 60 and/or IMD 16 function accordingly. In some
embodiments, display 60 may be a touch screen that enables the user
to select options directly from the display. In such cases, user
input mechanism 56 may be eliminated, although patient programmer
24 may include both a touch screen and user input mechanism 56. In
some embodiments, user interface 44 may also include audio
circuitry for providing audible instructions or sounds to patient
14 and/or receiving voice commands from patient 14.
[0088] User interface 44 may also include an LED or another
indication (e.g., via display 60) that provides confirmation to
patient 14 that an operation was carried out or that information
input via user input mechanism 56 was received. For example,
following cessation of therapy delivery according to a therapy
program, user interface 44 may prompt patient 14 to provide
feedback during the washout period. After patient 14 provides
feedback, user interface 44 may activate an LED to provide positive
feedback to patient 16 regarding the successfully received
information.
[0089] Processor 40 may comprise any combination of one or more
processors including one or more microprocessors, DSPs, ASICs,
FPGAs, or other equivalent integrated or discrete logic circuitry.
Accordingly, processor 40 may include any suitable structure,
whether in hardware, software, firmware, or any combination
thereof, to perform the functions ascribed herein to processor 40.
Memory 42 may include any volatile or nonvolatile memory, such as
RAM, ROM, EEPROM or flash memory. Memory 42 may also include a
removable memory portion that may be used to provide memory updates
or increases in memory capacities. A removable memory may also
allow patient data to be easily transferred to clinician programmer
22, or to be removed before patient programmer 24 is used by a
different patient.
[0090] Memory 42 stores, among other things, mood state information
50, therapy programs 52, and operating software 54. Memory 42 may
have any suitable architecture. For example, memory 42 may be
partitioned to store mood state information 50, therapy programs
52, and operating software 54. Alternatively, mood state
information 50, therapy programs 52, and operating software 54 may
each include separate memories that are linked to processor 40.
[0091] Therapy programs 52 portion of memory 42 stores data
relating to the therapy programs implemented by IMD 16. In some
embodiments, the actual settings for the therapy programs, e.g.,
the stimulation amplitude, pulse rate, pulse frequency and pulse
width data, are stored within therapy programs 52. In other
embodiments, an indication of each therapy program or group of
therapy programs, e.g., a single value associated with each therapy
program or group, may be stored within therapy programs 52, and the
actual parameters may be stored within memory 35 of IMD 16. The
"indication" for each therapy program or group may include, for
example, alphanumeric indications (e.g., Therapy Program Group A,
Therapy Program Group B, and so forth), or symbolic
indications.
[0092] Operating software 54 may include instructions executable by
processor 40 for operating user interface 44, telemetry module 46
and managing power source 48. Memory 42 may also store any therapy
data retrieved from IMD 16 during the course of therapy. The
clinician may use this therapy data to determine the progression of
the patient's disease in order to predict or plan a future
treatment.
[0093] Patient programmer 24 may communicate via wireless telemetry
with IMD 16, such as using RF communication or proximal inductive
interaction. This wireless communication is possible through the
use of telemetry module 46. Accordingly, telemetry module 46 may be
similar to the telemetry module contained within IMD 16. Telemetry
module 46 may also be configured to communicate with clinician
programmer 22 or another computing device via wireless
communication techniques, or direct communication through a wired
connection. Examples of local wireless communication techniques
that may be employed to facilitate communication between patient
programmer 24 and another computing device include RF communication
according to the 802.11 or Bluetooth specification sets, infrared
communication, e.g., according to the IrDA standard, or other
standard or proprietary telemetry protocols. In this manner, other
external devices may be capable of communicating with patient
programmer 24 without needing to establish a secure wireless
connection.
[0094] Power source 48 delivers operating power to the components
of patient programmer 24. Power source 48 may include a battery and
a power generation circuit to produce the operating power. In some
embodiments, the battery may be rechargeable to allow extended
operation. Recharging may be accomplished electrically coupling
power source 48 to a cradle or plug that is connected to an
alternating current (AC) outlet. In addition, recharging may be
accomplished through proximal inductive interaction between an
external charger and an inductive charging coil within patient
programmer 24. In other embodiments, traditional batteries (e.g.,
nickel cadmium or lithium ion batteries) may be used. In addition,
patient programmer 24 may be directly coupled to an alternating
current outlet recharge power source 48, or to power patient
programmer 24. Power source 48 may include circuitry to monitor
power remaining within a battery. In this manner, user interface 44
may provide a current battery level indicator or low battery level
indicator when the battery needs to be replaced or recharged. In
some cases, power source 48 may be capable of estimating the
remaining time of operation using the current battery.
[0095] FIG. 4 is a functional block diagram illustrating components
of clinician programmer 22, which may be similar to patient
programmer 24. Clinician programmer 22 may include a processor 70,
memory 72 including therapy programs 80, mood state information 82,
and operating software 84, user interface 74 including user input
mechanism 56 and display 60, telemetry module 76, and power source
78. The functions performed by each component may be similar to the
functions described above with reference to patient programmer 24.
Additionally, clinician programmer 22 may include more features
than patient programmer 24. For example, while clinician programmer
22 may be configured for more advanced programming features than
patient programmer 24. This may allow a user to modify more therapy
parameters with clinician programmer than with patient programmer
24. Patient programmer 24 may have a relatively limited ability to
modify therapy parameters of IMD 16 in order to minimize the
possibility of patient 14 selecting therapy parameters that are
harmful to patient 14. Similarly, clinician programmer 22 may
conduct more advanced diagnostics of IMD 16 than patient programmer
24.
[0096] As described in further detail below, processor 70 of
clinician programmer 22 may interrogate IMD 16 and/or patient
programmer 24 to retrieve any collected information stored within
memories 35, 42, such as information associated with therapy
programs, which may include information received from patient 14
relating to a mood state, or physiological parameter values. The
physiological parameter values may be values monitored during the
stimulation period, i.e., when IMD 16 is actively delivering
stimulation signals to target tissue within patient 14, or during
the washout period, i.e., the period following the stimulation
period. For example, memory 72 of clinician programmer 22 may
include software including instructions that cause processor 70 of
clinician programmer 22 to interrogate IMD 16 and/or patient
programmer 24. The information associated with therapy programs may
be stored within therapy program information portion 80 of memory
72.
[0097] In general, during a programming session, a clinician may
select values for a number of programmable therapy parameters in
order to define the electrical stimulation therapy to be delivered
by IMD 16 to patient 14. For example, the clinician may select a
combination of electrodes carried by one or more implantable leads,
and assigns polarities to the selected electrodes. In addition, the
clinician may select an amplitude, which may be a current or
voltage amplitude, a pulse width, and a pulse rate, in the case of
an IMD 16 that delivers stimulation pulses to patient 14. A group
of parameter values, including electrode configuration (electrode
combination and electrode polarity), amplitude, pulse width and
pulse rate, may be referred to as a therapy program in the sense
that they drive the neurostimulation therapy to be delivered to the
patient.
[0098] Programs selected during a programming session using
clinician programmer 22 may be transmitted to and stored within one
or both of patient programmer 24 and IMD 16. Where the programs are
stored in patient programmer 24, patient programmer 24 may transmit
the programs selected by patient 14 to IMD 16 for delivery of
neurostimulation therapy to patient 14 according to the selected
program. Where the programs are stored in IMD 16, patient
programmer 24 may receive a list of programs from IMD 16 to display
to patient 14, and transmit an indication of the selected program
to IMD 16 for delivery of neurostimulation therapy to patient 14
according to the selected program.
[0099] During a programming session, which may also be referred to
as a therapy program trial session, the clinician may specify a
program using clinician programmer 22 by selecting values for
various therapy parameters. When a program is specified, the
clinician may test the program by directing clinician programmer 22
to control IMD 16 to deliver therapy according to the program to
patient 14. The clinician or patient 14 may enter rating
information into the programming device for each tested program.
The rating information for a tested program may include information
relating to effectiveness of delivery of stimulation therapy
according to the program in treating symptoms of the patient, side
effects experienced by the patient due to the delivery of
neurostimulation therapy according to the program, or both. In the
case of psychiatric disorder stimulation therapy, efficacy
information may include an indication of patient mood state during
therapy delivery and during a washout period following therapy
delivery. The patient mood state information may include, for
example, patient feedback (received via patient programmer 22)
and/or physiological parameter values that are associated with a
particular patient mood state.
[0100] During the programming session, multiple therapy programs
may be tested (or trialed). That is, during a programming session,
IMD 16 may deliver therapy to patient 14 according to a first
therapy program, followed by a second therapy program, and so
forth, in order to assess the efficacy of each therapy program.
Clinician programmer 22 may maintain a session log in memory 72,
where the session log includes a listing of programs tested on
patient 14, rating information provided by the clinician or patient
14 for programs of the list, washout period information, and mood
state information. The listing may be ordered according to the
rating information in order to facilitate the selection of programs
from the list by the clinician.
[0101] For at least some of the tested therapy programs, at least
one characteristic of a washout period may be determined based on
one or more monitored physiological signals of patient 14. As
previously indicated, washout period characteristics may include
the duration of the washout period or one or more waveform
characteristics of one or more physiological signals during the
washout period.
[0102] FIGS. 5A-5E are schematic diagrams of a physiological signal
waveform prior to, during, and after delivery of electrical
stimulation signals by IMD 16. The diagrams shown in FIGS. 5A-5E
illustrate different types of physiological signal waveforms that
may occur during a period following delivery of stimulation
("post-stimulation period"), which may indicate the presence of one
or more carryover effects generated by therapy delivery according
to the therapy parameter values of a particular therapy program,
and may be used to determine a washout period characteristic. The
post-stimulation period may be immediately after the stimulation
period. The washout period generally refers to the portion of the
post-stimulation period during which carryover effects generated by
therapy delivery are present.
[0103] FIG. 5A illustrates a scenario in which therapy delivery
according to a first therapy program generates a stimulation effect
but does not generate a carryover effect, and, therefore, the
washout period has a duration of approximately 0 seconds (sec. or
s). Processor 70 of clinician programmer 22 may establish a
baseline characteristic of physiological signal 90 during a
pre-stimulation period 92, prior to delivery of stimulation by IMD
16 according to the first therapy program. While processor 70 is
primarily referred to throughout the description of FIGS. 5A-5E, in
other embodiments, a processor of another device, such as patient
programmer 24 or IMD 16, may monitor a physiological signal and
determine one or more washout period characteristics for a
particular therapy program.
[0104] In some embodiments, processor 70 establishes a baseline
state of physiological signal 90 prior to any stimulation delivery
by IMD 16 or prior to stimulation delivery by IMD 16 according to
the first therapy program or another therapy program. The baseline
state may be defined by a signal characteristic, such as an peak,
average or median amplitude value of physiological signal 90, a
trend in physiological signal 90 (e.g., a trend in inflection
points or a slope), a power level within one or more frequency
bands of physiological signal 90, a range of any of the
aforementioned signal characteristics, and the like. In some
embodiments, the baseline state of physiological signal 90 may be
based on the physiological signal 90 prior to therapy delivery
according to the first therapy program, i.e., prior to time
T.sub.1. For example, the baseline state may be a characteristic of
signal 90 that indicates patient 14 is in a baseline mood state,
which may be the mood state that occurs when therapy system 10 does
not deliver any therapy to patient 14. For example, if patient 14
is afflicted with MDD, the baseline mood state may be a severe or
moderately depressed mood state.
[0105] As shown in FIG. 5A, during the delivery of stimulation
signals by IMD 16, i.e., during stimulation period 94, the waveform
of physiological signal 90 may differ from the waveform observed
during pre-stimulation period 92. The first therapy program defines
a frequency of stimulation signals delivered to patient 14 during
stimulation period 94, i.e., the rate at which the stimulation
signals are delivered. Accordingly, stimulation signals in the form
of electrical pulses may be separated by an interval of time.
Stimulation period 94 refers to the entire stimulation session,
including the delivery of the stimulation signal and the intervals
between signals, rather than merely the period of time that
corresponds to the delivery of a stimulation signal.
[0106] The change in the amplitude of physiological signal 90
during stimulation period 94 indicates that therapy delivery
according to the first therapy program resulted in a stimulation
effect on patient 14. During stimulation period 94, physiological
signal 90 returns to the baseline amplitude value at time T.sub.3.
After therapy module 32 of IMD 16 (FIG. 2) terminates therapy
delivery according to the first therapy program, as indicated by
the post-stimulation period 96 beginning at time T.sub.2,
physiological signal 90 substantially returns to the baseline
state, e.g., the baseline signal characteristic determined during
pre-stimulation period 92.
[0107] Processor 70 may determine when physiological signal 90
returns to a baseline state by comparing the respective
characteristic of physiological signal 90 during post-stimulation
period 96 to the baseline state. For example, processor 70 may
compare an amplitude of signal 90 during post-stimulation period 96
to a baseline amplitude. In some cases, signal 90 may not return to
the exact baseline amplitude (or other signal characteristic
defining the baseline state) during post-stimulation period 96.
Thus, in some embodiments, processor 70 may determine that signal
90 has returned to the baseline state if the amplitude value of
signal 90 falls within a predetermined range of the baseline value,
such as about 1% to about 10% of the baseline amplitude value. The
clinician may select the predetermined percentage, which may depend
upon the type of physiological signal that is monitored.
[0108] The time windows for pre-stimulation period 92, stimulation
period 94, and post-stimulation period 96 may be fixed or may be
defined by the clinician, e.g., based on the actually time periods
during which the delivery of electrical stimulation therapy begins
and ends. For example, in some cases, the clinician may test one
therapy program longer than another, thereby resulting in a longer
stimulation period 94 for one therapy program compared to another
therapy program.
[0109] FIG. 5B illustrates a waveform of physiological signal 98
prior to, during, and after stimulation delivery according to a
second therapy program that generates a stimulation effect and an
immediate carryover effect. A baseline state of physiological
signal 98 may be established during a pre-stimulation period 92,
which may be prior to delivery of any stimulation by IMD 16 or
prior to delivery of stimulation by IMD 16 according to the second
therapy program. The baseline state of a physiological signal may
change over time. For example, if physiological signal 90 (FIG. 5A)
indicates the same patient parameter as physiological signal 98,
the baseline states of physiological signals 90, 98 may differ
depending on whether any prior therapy programs were tested prior
to the determination of the baseline states.
[0110] In some cases, if the first therapy program is tested prior
to the second therapy program, such that the pre-stimulation period
92 of FIG. 5B follows the post-stimulation period 96 of FIG. 5A,
the baseline state of physiological signal 98 may be characterized
by a higher amplitude value than the baseline state of
physiological signal 90 due to changes in the physiological
parameter of patient 14 that were generated based on therapy
delivery according to the first therapy program. Thus, processor 70
may implement an adaptive baseline state for a physiological signal
to account for physiological effects from prior therapy delivery.
However, as discussed above, in some examples, a single baseline
state may be established, e.g., at the beginning of the trial
stimulation. Processor 70 may generate the adaptive baseline state
by determining the baseline state for a physiological signal prior
to therapy delivery according to each tested therapy program.
[0111] After IMD 16 begins delivery of electrical stimulation to
patient 14 based on the second therapy program, an amplitude of
signal 98 increases, as shown in during stimulation period 94 in
FIG. 5B, thereby indicating the presence of a stimulation effect
from the delivery of therapy according to the second therapy
program. The second therapy program differs from the first program
in one or more respects. For example, the values of one or more
therapy parameters of the second therapy program may differ from
the values of the respective therapy parameters of the first
therapy program. As examples, the first and second therapy programs
may have different voltage or current amplitudes, signal durations,
total stimulation period durations, or may define different
electrode combinations for delivering therapy, and so forth. In
addition, the first and second therapy programs may be delivered to
different target tissue sites within patient 14. After termination
of therapy delivery according to the second therapy program,
physiological signal 98 remains at the elevated amplitude until
time T.sub.4. Thereafter, physiological signal 98 returns to a
baseline state, which was established during pre-stimulation period
92.
[0112] The washout period P.sub.1 associated with the second
therapy program may be defined as the period between time T.sub.4
and time T.sub.2, i.e., the end of the stimulation period 94. The
carryover effect shown by signal 98 in the example shown in FIG. 5B
may be characterized as an immediate carryover effect because of
its occurrence immediately after stimulation period 94. With some
immediate carryover effects, such as the one seen in FIG. 5B, the
change in physiological signal 98 is detected during stimulation
period 94 and carries over into post-stimulation period 96, after
IMD 16 terminates therapy delivery. In other embodiments, an
immediate carryover effect may occur although physiological signal
98 did not change during stimulation period 94. Processor 70 may
determine a characteristic of washout period P.sub.1 during washout
period P.sub.1, such as the peak amplitude of signal 98 during
washout period P.sub.1, the average or median amplitude during
washout period P.sub.1, a waveform morphology (e.g., slope of the
waveform or pattern in inflection points) during washout period
P.sub.1, and the like. In some embodiments, the one or more
characteristics of washout period P.sub.1 may be the duration of
washout period P.sub.1, which may be determined to be the duration
of time between time T.sub.4 and time T.sub.2.
[0113] In some embodiments, processor 70 may determine a
characteristic of stimulation period 94. The characteristic may
include, for example, a duration or percentage of time a
physiological signal 98 change from a baseline state was observed
during stimulation period 94, or a trend in physiological signal 98
waveform during stimulation period 94, a power level of the
physiological signal 98 measured in a particular frequency band
during stimulation period 94, ratios of power levels between
different frequency bands during stimulation period 94, and the
like. The stimulation period characteristic may be used to evaluate
the therapy program. For example, the stimulation period
characteristic may indicate the affect of the therapy delivery on
the physiological parameter of patient 12. In addition, in
embodiments in which a plurality of therapy programs are tested, a
stimulation period characteristic may be determined for each of the
therapy programs and may be used to compare the efficacy of the
therapy programs.
[0114] FIG. 5C illustrates a waveform of physiological signal 100
prior to, during, and after stimulation delivery according to a
third therapy program that generates a stimulation effect and an
immediate carryover effect. Again, a baseline state of
physiological signal 100 may be established during a
pre-stimulation period 92, prior to delivery of any stimulation by
IMD 16 prior to delivery of stimulation according to the third
therapy program in the case of an adaptive baseline state. After
IMD 16 begins delivery of electrical stimulation to patient 14
based on the third therapy program, an amplitude of signal 100
increases, thereby indicating a stimulation effect from therapy
delivery according to the third therapy program. After termination
of therapy delivery according to the third therapy program at time
T.sub.2, physiological signal 100 remains above the baseline
amplitude until time T.sub.5. Thereafter, physiological signal 100
returns to the baseline state, which was established generated
during pre-stimulation period 92.
[0115] The washout period P.sub.2 associated with the third therapy
program may be defined as the period between time T.sub.5 and time
T.sub.2, i.e., the end of the stimulation period 94. The carryover
effect shown by signal 100 in the example shown in FIG. 5C may be
characterized as an immediate carryover effect because of its
occurrence immediately after stimulation period 94. The carryover
effect resulting from therapy delivery by the third therapy program
is longer than the carryover effect resulting from the second
therapy program, shown in FIG. 5B, thus, the washout period P.sub.2
shown in FIG. 5C has a longer duration than washout period P.sub.1
shown in FIG. 5B.
[0116] FIG. 5D illustrates a waveform of physiological signal 102
prior to, during, and after delivery of stimulation according to a
fourth therapy program that does not generate a significant
stimulation effect, but generates a carryover effect within patient
14. Again, a baseline waveform of physiological signal 102 may be
established during a pre-stimulation period 92, prior to delivery
of any stimulation by IMD 16 or prior to delivery of stimulation
according to the fourth therapy program. After IMD 16 begins
delivery of electrical stimulation to patient 14 based on the
fourth therapy program, an amplitude of signal 102 remains
substantially similar to the baseline state of stimulation signal
102, i.e., as shown by signal 102 during the pre-stimulation period
92 in FIG. 5A. This indicates that therapy delivery according the
parameter values defined by the fourth therapy program does not
generate a stimulation effect within patient 14. That is, the
therapy delivery did not impact the physiological signal 102.
[0117] After termination of therapy delivery according to the
fourth therapy program, physiological signal 102 remains at or
below the baseline amplitude until time T.sub.6, at which time the
amplitude of the physiological signal 102 waveform increases. The
increase in amplitude of the physiological signal 102 waveform
during post-stimulation period 96 indicates that therapy delivery
according to the fourth therapy program generated a carryover
effect within patient 14. In addition, because the increase in
amplitude of the physiological signal 102 waveform did not occur
immediately after stimulation period 94, the carryover effect may
be characterized as a delayed carryover effect. With a delayed
carryover effect, the change in physiological signal 102 is
detected during post-stimulation period 96, with or without prior
detection of signal changes during stimulation period 94.
[0118] Physiological signal 102 returns to at or below the
amplitude of the baseline signal generated during the
pre-stimulation period 92 at time T7. Accordingly, a washout period
P.sub.3 associated with the fourth therapy program may be defined
as the duration between time T.sub.7 and T2. In other embodiments,
washout period P.sub.3 associated with the fourth therapy program
may be defined as the duration between time T.sub.7 and T.sub.6, as
shown in FIG. 5D, i.e., the actual duration of time at which
physiological signal 102 differs from the baseline state.
[0119] FIG. 5E illustrates a waveform of physiological signal 104
prior to, during, and after stimulation delivery according to a
fifth therapy program that does not generate a stimulation effect
or a carryover effect within patient 14. As FIG. 5E illustrates,
physiological signal 104 remains substantially the same during
pre-stimulation period 92, stimulation period 94, and
post-stimulation period 96. The duration of a washout period
associated with the fifth therapy program may be characterized as
approximately 0 seconds.
[0120] The physiological signals 90 (FIG. 5A), 98 (FIG. 5B), 100
(FIG. 5C), 102 (FIG. 5D), and 104 (FIG. 5E) may be any suitable
signal detectable within patient 14 that changes in response to
delivery of therapy to patient 14, and indicates a physiological
parameter of patient 14 that varies as a function of a patient mood
state, such as an anxious state or a depressive state. Examples of
suitable physiological signals include, but are not limited to,
signals indicating a patient's heart rate, respiratory rate, ECG
morphology, core temperature, electrodermal activity, EEG or ECoG
activity, thermal sensing or facial EMG activity.
[0121] While the examples of stimulation effects and carryover
effects in FIGS. 5B-5D illustrate an increase in an amplitude of a
physiological signal during stimulation period 94 and/or during
post-stimulation period 96, in some embodiments, the physiological
signal may decrease in amplitude relative to the baseline state
during at least one of the stimulation period 94 or
post-stimulation period 96. Accordingly, if the physiological
signal returns to a baseline state, the signal may increase in
value.
[0122] FIG. 6 is a schematic diagram illustrating different
examples embodiments of sensing module 26 (FIG. 1) that may be used
to monitor a physiological parameter of patient 14 in order to
detect a carryover effect from therapy delivery. As indicated above
with respect to FIG. 1, signals generated by sensing module 26,
which may be implanted or external to patient 14, may be
transmitted to IMD 16 or at least one of programmers 22, 24 via
wireless signals or a wired connection. IMD 16 or programmers 22,
24 may monitor and analyze the signals from sensing module 26 to
detect a carryover effect from therapy delivery, and determine one
or more characteristics of a washout period following active
therapy delivery.
[0123] In some embodiments, sensing module 26 may include ECG
electrodes, which may be carried by an ECG belt 110. ECG belt 110
incorporates a plurality of electrodes for sensing the electrical
activity of the heart of patient 14. In the embodiment shown in
FIG. 6, ECG belt 110 is worn by patient 14. The heart rate and, in
some embodiments, ECG morphology of patient 14 may be monitored
based on the signal provided by ECG belt 110. Examples of suitable
ECG belts for sensing the heart rate of patient 14 are the "M" and
"F" heart rate monitor models commercially available from Polar
Electro OY of Kempele, Finland. In some embodiments, instead of ECG
belt 110, patient 14 may wear a plurality of ECG electrodes (not
shown in FIG. 6) attached, e.g., via adhesive patches, at various
locations on the chest of patient 14, as is known in the art. An
ECG signal derived from the signals sensed by such an array of
electrodes may enable both heart rate and ECG morphology
monitoring. In addition to or instead of ECG belt 110, IMD 16 may
sense the patient's heart rate, e.g., using electrodes on a housing
of IMD 16, electrodes of leads 20, electrodes coupled to other
leads or any combination thereof.
[0124] In other embodiments, sensing module 26 may include a
respiration belt 112 that outputs a signal that varies as a
function of respiration of the patient may also be worn by patient
14 to monitor activity to determine whether patient 14 is in a
particular mood state or to determine the stimulation or carryover
effects of therapy delivery on patient 14. For example, in an
anxious mood state, the patient's respiration rate may increase
relative to a baseline respiration rate associated with a
non-anxious mood state of patient 14. Respiration belt 112 may be a
plethysmograpy belt, and the signal output by respiration belt 112
may vary as a function of the changes is the thoracic or abdominal
circumference of patient 14 that accompany breathing by patient 14.
An example of a suitable respiration belt is the TSD201 Respiratory
Effort Transducer commercially available from Biopac Systems, Inc.
of Goleta, Calif. Alternatively, respiration belt 112 may
incorporate or be replaced by a plurality of electrodes that direct
an electrical signal through the thorax of patient 14, and
circuitry to sense the impedance of the thorax, which varies as a
function of respiration of patient 14, based on the signal. The
respiration belt may, for example, be used to generate an impedance
cardiograph (ICG), which detects properties of blood flow in the
thorax. In some embodiments, the ECG and respiration belts 110, 112
may be a common belt worn by patient 14.
[0125] In some embodiments, sensing module 26 may also include
electrode 114, which may be a surface electrode or intramuscular
electrode. Electrode 114 may be positioned to monitor muscle
activity (e.g., EMG), the temperature of the patient's facial skin
(e.g., a thermal sensing electrode), or the moisture level of the
patient's skin (e.g., via electrodermal activity). Alternatively,
electrode 114 may be positioned to monitor the muscle activity,
temperature, moisture level or extent of perfusion of other regions
of the patient's body, such as an arm, leg or torso. Electrode 114
may be coupled to clinician programmer 22, or another device, which
may monitor the signals generated by electrode 114 as a function of
the physiological parameter and transmit the signals to clinician
programmer 22. Each of the types of sensing device 110, 112, and
114 described above may be used alone or in combination with each
other, as well as in addition to other sensing devices.
[0126] During a programming session during which IMD 16 delivers
therapy to patient 14 according to a plurality of therapy programs,
it may be desirable to time the trialing of the different therapy
programs such that one or more carryover effects from stimulation
delivery according to the prior-trialed therapy program have
substantially dissipated. That is, during a programming session, it
may be desirable to determine the times at which different therapy
programs should be applied, and the time intervals between
successive programs based on one or more carryover effects.
[0127] Waiting to deliver trial stimulation according to a
particular therapy program until after one or more carryover
effects from a prior-trialed therapy program may help reduce or
even eliminate contamination between therapy programs. For example,
with respect to the example of FIG. 5B, which illustrates
physiological signal 98 prior to, during, and after stimulation
delivery according to a second therapy program, it may be
undesirable to initiate therapy delivery according to a different
therapy program until after time T.sub.4, which indicates the end
of the washout period and the time at which carryover effects from
therapy delivery according to the second therapy program have
substantially dissipated. Initiating therapy delivery according to
a different therapy program between times T.sub.2 and T.sub.4 may
result in inaccurate therapeutic effects on patient 14 due to
lingering carryover effects from the previous therapy program. For
example, the amplitude increase of physiological signal 98
occurring between times T.sub.2 and T.sub.4 may result in an
increased amplitude of physiological signal 98 in response to the
therapy delivery by the subsequently-trialed therapy program due to
cumulative or interactive effects of the stimulation from the
therapy programs.
[0128] FIG. 7A is a flow diagram illustrating an example technique
for automatically timing delivery of therapy programs during a
programming session based on the duration of a washout period. The
automatic technique for timing trials of therapy delivery may more
accurately and precisely time trials of different therapy programs
to help reduce contamination between the stimulation and
post-stimulation effects of the trialed therapy programs compared
to a technique in which a clinician manually monitors a
physiological signal of patient 14 or manually observes patient 14
to estimate when one or more carryover effects from a trialed
therapy program have substantially dissipated.
[0129] The manual techniques for timing the delivery of therapy
programs during a trial period are susceptible to human error. For
example, as previously indicated, in some cases, a baseline state
of a physiological signal may change during a programming session.
While processor 70 of clinician programmer 22 may readily adapt the
baseline state of the physiological signal to the patient's current
condition, a clinician may find it difficult, cumbersome or
time-consuming to continually monitor the patient's baseline state.
As another example, the clinician may not be able to easily
manually observe subtle changes to a physiological signal during
stimulation period 94 and post-stimulation period 96. Processor 70
implements various algorithms to compare the physiological signal
waveform to a threshold value or pattern template in order to
detect a stimulation effect or carryover effect. Accordingly, the
clinician may not detect the subtle changes to a physiological
signal through visual observation that processor 70 may be to
detect with the comparison algorithms. Changes to physiological
signals that indicate a change to a patient's mood state may be
subtle.
[0130] While clinician programmer 22 and its processor 70 are
primarily referred to throughout the description of FIGS. 7A-7C, as
well as FIGS. 8-16, in other embodiments, processor 40 of patient
programmer 24 or a processor of another device may perform any of
the techniques described with respect to FIG. 7A or any of the
other figures. Under the control of a clinician, e.g., via
clinician programmer 22, processor 34 of IMD 16 may control therapy
module 32 to deliver electrical stimulation therapy to patient 14
according to the stimulation parameter values defined by a therapy
program (120). For example, the clinician may select the therapy
program from a list of therapy programs stored in clinician
programmer 22 (FIG. 3) by interacting with user interface 74.
Processor 70 of clinician programmer 22 may then transmit a control
signal to processor 34 of IMD 16 by the telemetry module 76 of
clinician programmer 22. The control signal may set forth the
parameter values of the therapy program or may merely be an
identifier associated with the therapy program, and the actual
parameter values may be stored within memory 35 of IMD 16 and
associated with the identifier in memory 35.
[0131] As an alternative to a clinician-selected therapy program,
processor 70 of programmer 22 may automatically select the
parameter values for the therapy program. For example, processor 70
may implement a methodical system of identifying potentially
beneficial therapy parameter values for patient 14. In one
embodiment, processor 70 may implement a tree-based technique for
selecting the therapy program. A programming tree structure may
include a plurality of levels that are associated with a different
therapy parameter. The tree may include nodes that are connected to
nodes of adjacent levels, whereby each node defines values for at
least one therapy parameter. A clinician or patient 14 may interact
with processor 70 via user interface 74 in order to create a
program path by moving through one node at each level of the tree
according to efficacy feedback from patient 14 and/or one or more
sensors that detect physiological parameters of patient 14.
[0132] Examples of tree-based techniques for modifying a therapy
program or generating a new therapy program are described in
commonly-assigned U.S. patent application Ser. No. 11/799,114 to
Gerber et al., entitled, "TREE-BASED ELECTRICAL STIMULATION
PROGRAMMING FOR PAIN THERAPY," and filed on Apr. 30, 2007;
commonly-assigned U.S. patent application Ser. No. 11/799,113 to
Gerber et al., entitled, "TREE-BASED ELECTRICAL STIMULATOR
PROGRAMMING," and filed on Apr. 30, 2007; and commonly-assigned
U.S. patent application Ser. No. 11/414,527 to Gerber et al.,
entitled, "TREE-BASED ELECTRICAL STIMULATOR PROGRAMMING," and filed
on Apr. 28, 2006, which are each incorporated herein by reference
in their entireties.
[0133] In another embodiment, processor 70 may implement a genetic
algorithm-based technique for selecting the therapy program, such
as the one described in commonly-assigned U.S. Pat. No. 7,239,926
to Goetz et al., entitled, "SELECTION OF NEUROSTIMULATION PARAMETER
CONFIGURATIONS USING GENETIC ALGORITHMS," which issued on Jul. 3,
2007 and is incorporated herein by reference in its entirety. In
one embodiment described in U.S. Pat. No. 7,239,926 to Goetz et
al., genetic algorithms guide the selection of stimulation
parameter values by suggesting the parameter values that are most
likely to be efficacious given the results of tests already
performed during an evaluation (or programming) session. Genetic
algorithms encode potential solutions to a problem as members of a
population of solutions. This population is then judged based on a
fitness function. The best performers, i.e., the best fit
solutions, are then retained and a new generation is created based
upon their characteristics. The new generation is composed of
solutions similar in nature to the best performers of the previous
generation.
[0134] Other suitable techniques for selecting a therapy program
include the decision-tree based techniques described in
commonly-assigned U.S. patent application Ser. No. 10/767,545 to
Goetz, entitled, "SELECTION OF NEUROSTIMULATOR PARAMETER
CONFIGURATIONS USING DECISION TREES," which was filed on Jan. 29,
2004, and U.S. Pat. No. 6,901,754 to Goetz, entitled, "SELECTION OF
NEUROSTIMULATOR PARAMETER CONFIGURATIONS USING BAYESIAN NETWORKS,"
which was filed on Jan. 29, 2004. The entire content of U.S. patent
application Ser. No. 10/767,545 and U.S. Pat. No. 6,901,754 is
incorporated herein. As described in U.S. patent application Ser.
No. 10/767,545 to Goetz, a parameter configuration search algorithm
may be used to guide the clinician and/or processor 70 in the
selection of parameter configurations for a therapy program. The
search algorithm relies on a decision tree to identify potential
optimum parameter configurations, where the decision tree
interactively guides the clinician by suggesting the configurations
that are most likely to be efficacious given the results of
determinations along the path of the decision tree based on
efficacy observations already performed during an evaluation
session.
[0135] As described in U.S. Pat. No. 6,901,754 to Goetz, processor
70 or a clinician may execute a parameter configuration search
algorithm that relies on a Bayesian network structure that encodes
conditional probabilities describing different states of the
parameter configuration. The Bayesian network structure may provide
a conditional probability table that represents causal
relationships between different parameter configurations and
clinical outcomes. The search algorithm uses the Bayesian network
structure to infer likely efficacies of possible parameter
configurations based on the efficacies of parameter configurations
already observed.
[0136] Processor 70 may monitor one or more physiological signals
of patient 14 (122) at least during the stimulation period, and, in
some cases, prior to the stimulation period to determine a baseline
physiological parameter state. During the trial therapy session,
processor 70 may control IMD 16 to deliver therapy to patient 14
according to the therapy program for a limited period of time. For
example, after about 20 seconds to about 60 minutes, such as about
30 seconds to about one minute, processor 70 may control IMD 16 to
stop therapy delivery (123). Alternatively, IMD 16 may be
preprogrammed to automatically stop therapy delivery (123)
independently of any clinician programmer 22 or clinician control.
As another alternative, processor 60 may generate a prompt for the
clinician to take an action or approve an action.
[0137] After IMD 16 has stopped therapy delivery according to the
trialed therapy program (123), processor 70 of programmer 22 may
continue monitoring the physiological signal during the
post-stimulation period until the monitored physiological signal
returns to a particular state, which may be the baseline state
(125, 126), thereby indicating one or more carryover effects from
the therapy delivery have substantially terminated. The baseline
state may be stored in memory 72 (FIG. 4) of clinician programmer
22 or a memory of another device. The baseline state may be an
exact baseline value of the physiological signal at the time prior
to the stimulation period, or may be a value substantially close to
the baseline value, such as within certain percentage (e.g., within
about 5% to about 25%, depending on the type of signal). For
example, in some cases, the physiological signal may return to the
baseline state (125, 126), but may have an average amplitude value
that is greater than the amplitude value prior to the stimulation
period. In other embodiments, processor 70 of programmer 22 may
determine when the physiological signal returns to another state,
which may be selected by the clinician and may or may not be based
on the baseline state. In some embodiments, the state may be
defined as a single value or a range of values.
[0138] As previously indicated, processor 70 may determine the
baseline state of the relevant physiological signal prior to
therapy delivery according to the trialed therapy program (120) or
prior to any therapy delivery by IMD 16. Processor 70 may determine
whether the signal returned to a baseline state using different
techniques, which may depend on the physiological signal
characteristic that characterizes the baseline state of the
signal.
[0139] In embodiments in which the baseline state of the
physiological signal is characterized by a peak amplitude value,
average amplitude value, mean amplitude value or another amplitude
value, processor 70 may compare the amplitude value of the
physiological signal to the relevant amplitude value, which may be
stored as a threshold value in memory 72. Rather than continuously
comparing the amplitude of the physiological signal, processor 70
may sample the physiological signal during the post-stimulation
period 96 (FIGS. 5A-5E) and average the amplitude of the
physiological signal for each sampled period, which may be, e.g., a
few milliseconds or a few seconds in duration.
[0140] In embodiments in which the baseline state of the
physiological signal is characterized by a trend in the
physiological signal waveform, processor 70 may compare a trend in
the physiological signal during the post-stimulation period 96
(FIGS. 5A-5E) to a template stored in memory 72. A similar
technique for comparing the physiological signal waveform to a
template is described below with respect to FIG. 14. In embodiments
in which the baseline state of the physiological signal is
characterized by a frequency band characteristic of the
physiological signal waveform, such as an energy level in a
frequency band or a ratio of energy levels in more than one
frequency band, processor 70 may compare the relevant frequency
band characteristics of the physiological signal waveform during
the post-stimulation period 96 (FIGS. 5A-5E) to a template or
threshold value stored in memory 72. A similar technique for
analyzing a frequency band characteristic of a physiological signal
waveform is described below with respect to FIG. 15.
[0141] If processor 70 determines that the physiological signal has
not returned to the baseline state (126), processor 70 may continue
monitoring the physiological signal (125) until the signal returns
to the baseline state, thereby indicating that one or more
carryover effects from therapy delivery according to the therapy
program have substantially dissipated. On the other hand, if
processor 70 determines that the physiological signal has returned
to the baseline state (126), processor 70 may initiate the delivery
of trial stimulation according to another therapy program (128).
Again, processor 70 may automatically initiate the trialing of
another therapy program or may initiate the therapy delivery
according to another therapy program after providing a notification
to a clinician and receiving approval from the clinician to proceed
to the next therapy program.
[0142] For example, in the example shown in FIG. 5A, for example,
physiological signal 90 returns to the baseline state during
stimulation period 94 and there is substantially no carryover
effect, and, therefore, processor 70 may automatically determine
that the physiological signal 90 is at the baseline state
approximately immediately following the cessation of therapy
delivery. As another example, in the example shown in FIG. 5B,
processor 70 may automatically determine that physiological signal
98 returns to the baseline state at approximately time T.sub.4,
which occurs after the end of the stimulation period 94 and denotes
the end of the washout period P.sub.1. With respect to delayed
carryover effects, as shown with respect to physiological signal
102 in FIG. 5D, processor 70 may continue monitoring physiological
signal 102 for a period of time following stimulation period 94 in
order to detect the delayed carryover effect. In the example shown
in FIG. 5D, processor 70 may automatically determine that
physiological signal 98 returns to the baseline at approximately
time T.sub.7.
[0143] Processor 70 may control IMD 16 to delivery therapy
according to another therapy program (i.e., a "next-trialed"
therapy program) (128). In some embodiments, processor 70 may
generate an indication to the clinician that the next therapy
program may be trialed, e.g., by a visible (e.g., a green light
that lights up), audible, or somatosensory indication (e.g., a
vibration). The clinician may then select a therapy program to test
and processor 70 may control IMD 16 to delivery therapy according
to the clinician-selected therapy program. As another example, the
clinician may provide input indicating approval for processor 70 to
automatically select another therapy program to test.
Alternatively, processor 70 may generate the indication that the
next therapy program may be tested and automatically select another
therapy program to test. The indication may, therefore, be an
indication that another therapy program is being tested in addition
to being an indication that one or more carryover effects from the
prior-trialed therapy program have substantially dissipated.
[0144] As with the prior-trialed therapy program, the clinician or
processor 70 may select the next-trialed therapy program from a
list of therapy programs stored in clinician programmer 22 (FIG. 3)
by interacting with user interface 44, or processor 70 of clinician
programmer 22 may automatically select the second therapy program.
The therapy parameter values for the second therapy program may be
stored within IMD 16 and/or within clinician programmer 22.
[0145] In one embodiment, as described by U.S. Pat. No. 7,239,926
to Goetz et al., processor 70 may receive an indication of observed
efficacy of the prior-trialed therapy program, and select another
therapy program for IMD 16 based on the indication of observed
efficacy and a genetic algorithm. A genetic algorithm may suggest
cross-over between different solutions identified by the genetic
algorithm or mutation of one or more solutions identified by the
genetic algorithm, or random electrode changes.
[0146] FIG. 7B is a flow diagram illustrating another example
technique for automatically timing delivery of therapy programs
during a programming session based on the duration of a washout
period. Just as with the technique shown in FIG. 7A, therapy may be
delivered to patient 14 according to a therapy program (120), and
processor 70 may monitor a physiological signal of patient that
changes as the mood state of patient 14 changes (122). Upon the
cessation of therapy delivery according to the therapy program
(123), processor 70 may determine whether the physiological signal
has returned to the baseline state (126). If the physiological
signal has not returned to the baseline state, processor 70 may
continue monitoring the physiological signal (125).
[0147] If the physiological signal has returned to the baseline
state, processor 70 may determine whether a minimum waiting period
has passed (129). The minimum waiting period may be, for example, a
minimum period of time following the end of the stimulation period
94 for the trial therapy delivery according to the therapy program.
The minimum waiting period may be selected by the clinician or may
be pre-programmed into clinician programmer 22, e.g., by the
manufacturer or distributor of IMD 16 or programmer 22. For
example, the minimum waiting period may be minimum desired spacing
between the trial sessions for different therapy programs.
[0148] If the minimum waiting period has passed, processor 70 may
initiate therapy delivery to patient 14 according to another
therapy program (128). If the minimum waiting period has not
passed, processor 70 may continue monitoring the physiological
signal (125) and determine whether the signal is at the baseline
state (126) until the minimum waiting period has passed (129) prior
to initiating therapy delivery according to the next trialed
therapy program (128). Processor 70 may continue comparing the
physiological signal to the baseline state in order to detect one
or more delayed carryover effects. Timing the trialing of therapy
programs using a minimum waiting period may help regulate the rate
at which processor 70 switches between therapy programs during the
programming session, and helps minimize the possibility that
processor 70 will not detect a delayed carryover effect.
[0149] FIG. 7C is a flow diagram illustrating another example
technique for automatically timing delivery of therapy programs
during a programming session based on the duration of a washout
period. Therapy may be delivered to patient 14 according to a
therapy program (120), and processor 70 may monitor a physiological
signal of patient that changes as the mood state of patient 14
changes (122). Upon the cessation of therapy delivery according to
the therapy program (123), processor 70 may control the application
of a stimulus to actively drive of the physiological signal to a
baseline state (124). The physiological signal may be actively
driven to the baseline state using any technique that increases the
speed at which the physiological signal returns to the baseline
state compared to the passive return to the baseline state, i.e.,
without substantial interference from an external stimulus.
[0150] For example, in embodiments in which therapy system 10 is
used to manage a MDD of patient 14, processor 70 may present an
unpleasant or distressing image (e.g., a picture or video) to
patient 14 via display 60 (FIG. 4) of clinician programmer 20 or
prompt the clinician or another user to present the unpleasant
image to patient 14. As another example, IMD 16 may deliver
electrical stimulation to patient 14 to cause the physiological
signal to return to a baseline state. For example, in embodiments
in which a therapy system is used to manage pain of patient 14
(e.g., in the case of spinal cord stimulation), IMD 16 may provide
stimulation to patient 14 to cause pain or processor 70 may prompt
patient 14 to engage an activity that is known to cause patient 14
pain. Other techniques for expressly driving the physiological
signal to a baseline state are contemplated, and may be dependent
on the type of patient condition the therapy system is used to
manage.
[0151] After the attempt to actively drive the physiological signal
to the baseline state, processor 70 may determine whether the
physiological signal has returned to the baseline state (126). If
the physiological signal has not returned to the baseline state,
processor 70 may control the application of another stimulus to
attempt to actively drive the physiological signal to the baseline
state (124). If the physiological signal has returned to the
baseline state, processor 70 may initiate the delivery of therapy
to patient 14 according to another therapy program (128). In some
embodiments, processor 70 may also wait the minimum wait period (as
discussed with respect to FIG. 7B) prior to initiating therapy
delivery according to the next-trialed therapy program.
[0152] Determining the times at which different therapy programs
should be applied, and the time intervals between successive
programs based on one or more carryover effects may be used to time
the testing of therapy programs for other types of therapy
applications. Accordingly, the techniques shown in FIGS. 7A-7C are
applicable to many types of therapy systems 10 in addition to or
instead of DBS system 10 shown in FIG. 1.
[0153] In some cases, a washout period may be used to track the
effects of DBS (or other types of therapy) on sensed physiological
parameters of patient 14 and identify one or more carryover effects
from the stimulation. In the case of therapy used to manage a
psychiatric disorder of patient 14, the physiological parameters
may indicate changes in the patient's mood state. For example, a
change in the patient's respiratory rate, heart rate, and galvanic
skin response may indicate changes in the patient's overall arousal
level or anxiety level. As another example, a change in the
patient's facial expression (e.g., monitored by EMG) or facial
flushing (e.g., monitored by thermal sensing) may indicate a change
in an mood state. Changes in the patient's EEG or ECoG signal,
detected by template matching, peak detection, comparison to a
threshold amplitude or energy level value may, may also indicate a
change in the patient's mood state. An example technique for
performing template matching between the physiological signal
waveform and a template waveform is described below with reference
to FIG. 14.
[0154] In some embodiments, changes to a patient's mood state
during the washout period, i.e., in response to therapy delivery
may be indicative of the efficacy of therapy, while in other
embodiments, changes to the patient's mood state may be indicative
of a undesirable response to the therapy delivery. For example, if
therapy system 10 provides therapy to patient 14 to manage MDD, a
slight increase in emotional arousal indicated by a physiological
parameter of patient 14 during the washout period may indicate a
positive response to the therapy. On the other hand, if therapy
system 10 provides therapy to patient 14 to manage an anxiety
disorder, a slight increase in emotional arousal during the washout
period may indicate a negative response to therapy because the
increase in emotional arousal may suggest an increase in the
patient's anxiety level.
[0155] Changes in a physiological parameter of patient 14 that is
suggestive of the patient's mood state may be assessed by
monitoring the physiological signal during pre-stimulation period
92, stimulation period 94, and post-stimulation period 96 (FIGS.
5A-5E). As described above, the time windows for pre-stimulation
period 92, stimulation period 94, and post-stimulation period 96
may be fixed or may be defined by the clinician, e.g., based on the
actually time periods during which the delivery of electrical
stimulation therapy begins and ends.
[0156] FIG. 8 is a flow diagram illustrating an example technique
for automatically determining a characteristic of a washout period
following therapy delivery by a therapy program and associating the
washout period characteristic with the therapy program. The
characteristic of the washout period may be used to evaluate the
efficacy of the therapy program. Examples of suitable washout
period characteristics include, but are not limited to, a duration
of the washout period, an amplitude of the physiological signal
waveform during the washout period, a trend in the physiological
signal waveform during the washout period, a power level of the
physiological signal measured in a particular frequency band of the
physiological signal waveform, ratios of power levels between
different frequency bands, and the like. While psychiatric disorder
therapy is primarily referred to in the description of FIG. 8, as
well as FIGS. 9-10, in other embodiments, therapy programs for
managing other patient conditions may be evaluated and ordered
based on washout period characteristics.
[0157] Prior to delivering electrical stimulation therapy (or
another type of therapy) to patient 14 according to a therapy
program, processor 70 may monitor a physiological parameter of
patient 14 (131). For example, processor 70 may receive input from
sensing module 26 (FIG. 1) during the pre-stimulation period 92
(FIGS. 5A-5E). Processor 70 may determine a baseline state for the
monitored physiological signal, e.g., by selecting an amplitude
value or waveform trend during the pre-stimulation period 92 (131).
In one embodiment, processor 70 determines an average or median
amplitude of the physiological signal waveform during the
pre-stimulation period 92, which may be a predetermined period of
time prior to therapy delivery, such as about 30 seconds to about
10 minutes, and sets the average or median amplitude as a baseline
amplitude value. Other time ranges for the pre-stimulation period
92 are also contemplated. In another embodiment, processor 70 may
determine the peak amplitude value of the physiological signal
waveform during the pre-stimulation period, and set the peak
amplitude value as the baseline value. In other embodiments,
processor 70 may determine a trend of the physiological signal
waveform during the pre-stimulation period, and set the trend as a
baseline waveform.
[0158] Processor 70 may control IMD 16 to deliver therapy to
patient 14 according to a therapy program (132), which may be
clinician-selected or automatically selected by clinician
programmer 22. Processor 70 may monitor one or more physiological
signals of patient 14 during the stimulation period 94 (FIGS.
5A-5E) (134). For example, processor 70 may determine whether the
therapy delivery had a stimulation effect on patient 14 by
comparing the physiological signal sensed during stimulation period
94 to the baseline state. As one example, if the peak amplitude of
the physiological signal waveform during the stimulation period 94
exceeds a baseline amplitude value, the physiological signal may
indicate that the therapy delivery according to the therapy program
had an effect on patient 14.
[0159] Processor 70 may control IMD 16 to terminate active therapy
delivery (136). In some embodiments, IMD 16 may be preprogrammed to
actively deliver electrical stimulation signals to patient 14 for a
predetermined time period, such as about 1 minute to about 60
minutes, although other stimulation period durations are
contemplated. Thus, in some embodiments, IMD 16 may automatically
terminate active therapy delivery independently of any control by
clinician programmer 22. Processor 70 may monitor the physiological
signal during the post-stimulation period 96 (FIGS. 5A-5E) (138)
and determine whether the physiological signal changed from the
baseline state during the post-stimulation period 96, e.g., by
comparing one or more characteristics of the physiological signal
sensed during the post-stimulation period 96 to the baseline state
established during the pre-stimulation period 92 (140). If
processor 70 does not detect a change in the physiological signal
from the baseline state during the post-stimulation period 96
(140), processor 70 may generate an indication that indicates the
therapy delivery according to the therapy program did not result in
a carryover effect (142). The no carryover effect indication may be
a value, flag or signal that is stored in memory 72 (FIG. 4) of
clinician programmer 22 and associated with the therapy
program.
[0160] If the baseline state is characterized by a threshold
amplitude value, processor 70 may compare a peak, average, median
or any other amplitude value of the signal during a the
post-stimulation period 96 to a baseline amplitude value in order
to determine whether the physiological signal differs from the
baseline state during the post-stimulation period 96. The peak,
average, median or other amplitude value that is compared to the
baseline amplitude value may be the amplitude value during a
particular time range following the stimulation period 94. For
example, processor 70 may compare the peak, average or median
amplitude value of the physiological signal during a one minute
period following stimulation period 94 to the baseline amplitude
value. The time period may be selected by the clinician, and may be
long enough to confirm that there are no delayed carryover effects
from the therapy delivery.
[0161] In other embodiments, processor 70 may determine whether the
physiological signal differs from the baseline by comparing a trend
in the physiological signal during the particular time range of the
post-stimulation period to a template. For example, processor 70
may compare the physiological signal during the particular time
range following the stimulation period 94 to a template to
determine whether the physiological signal differs from the
baseline. In one embodiment, processor 70 implements a temporal
correlation technique, during which processor 70 samples the
physiological signal with a sliding window and compares the sample
to a template to determine whether the sampled signal correlates
well with the template. For example, processor 70 may perform a
correlation analysis by moving a window along a digitized plot of
the amplitude of the measured physiological signals at regular
intervals following the stimulation period 94, such as between
about one millisecond to about one second intervals, to define a
sample of the physiological signal. The sample window may be slid
along the plot of the physiological signal waveform until a
correlation is detected between the waveform of the baseline
template and the waveform of the sample of the physiological
defined by the window.
[0162] By moving the window at regular time intervals, multiple
sample periods are defined. The correlation may be detected by, for
example, matching multiple points between the template waveform and
the waveform of the plot of the physiological signal over time, or
by applying any suitable mathematical correlation algorithm between
the sample in the sampling window and a corresponding set of
samples stored in the template waveform. As examples, if rate of
change (i.e., the slope) of the monitored physiological signal
immediately following the stimulation period 94 correlates to the
slope of a trend template, the physiological signal may indicate a
lack of a carryover effect from the therapy delivery. As another
example, if inflection points in the physiological signal waveform
substantially correlate to a template immediately following
stimulation period 94, the physiological signal may indicate a lack
of a carryover effect from the therapy delivery.
[0163] In another embodiment, processor 70 implements a frequency
correlation technique, during which processor 70 analyzes the
physiological signal in the frequency domain to compare selected
frequency components of the sensed physiological signal to
corresponding frequency components of the template signal. In each
of the embodiments described above, the one or more templates or
baseline amplitude values may be stored within memory 72 of
clinician programmer 22 or another device.
[0164] If processor 70 detects a change in the physiological signal
from the baseline value or waveform during the post-stimulation
period (140), processor 70 may determine a characteristic of a
washout period (144). The washout period indicates the period
during the post-stimulation period 96 in which a carryover effect
from delivery of therapy according to the therapy program is
observed, which may be determined by comparing the physiological
signal to the baseline state. The washout period may be the period
during which the physiological signal substantially differs from
the baseline state by at least a threshold amount.
[0165] In one embodiment, the characteristic of the washout period
may include the duration of the washout period. Processor 70 may
determine the duration of the washout period by determining when
the physiological signal returns to the baseline state during the
post-stimulation period 96. The duration of the washout period may
then be the duration of time between the end of stimulation period
94 (e.g., when IMD 16 terminates therapy delivery or when the final
electrical stimulation signal according to the therapy program is
delivered) and the time at which the physiological signal returns
to the baseline state. In some situations in which the
physiological parameter indicates a delayed carryover effect,
processor 70 may determine the duration of the washout period by
determining when processor 70 determined that the physiological
signal differs from the baseline state during the post-stimulation
period 96 and when the signal returns to the baseline state during
the post-stimulation period 96. However, as previously discussed,
in some cases, despite the presence of a delayed carryover effect,
a duration of a washout period may be considered to be the duration
of time between the end of stimulation period 94 and the time at
which the signal returns to the baseline state.
[0166] In other embodiments, the characteristic of the washout
period may include the peak amplitude value, average amplitude,
median amplitude value or any other amplitude value of the
physiological signal during the washout period. The characteristic
of the washout period may also be a pattern in the physiological
signal waveform over time, such as a slope or trend in the
inflection points, or one or more frequency band components of the
physiological signal. In some cases, processor 70 may determine
more than one characteristic of the washout period.
[0167] After determining the one or more characteristics of the
washout period (144), processor 146 may associate the determined
washout period characteristic with the therapy program (146) and
store the characteristic in memory 72 (FIG. 4) of clinician
programmer 22 or another device, such as patient programmer 24, IMD
16 or a different device. If there are more therapy programs to
test during the trialing session (148), processor 70 may establish
another baseline for the pre-stimulation period prior to delivery
of therapy according to the next-trialed therapy program (131), and
repeat the process to establish one or more washout period
characteristics for the next-trialed therapy program.
Alternatively, processor 70 may utilize a previously established
baseline. If there are no more therapy programs to test, processor
70 may not take any further action with respect to determining
washout period characteristics associated with trialed therapy
programs.
[0168] Changes in a physiological signal during the
post-stimulation period 96 may be desirable or undesirable,
depending on the type of response to the therapy program that is
evoked, as well as the intended outcome of the therapy delivery.
For example, slight increases in emotional arousal caused by
stimulation may be beneficial to a patient with MDD, if it does not
interfere with normal function or cause the patient to achieve an
emotional state not considered normal (e.g., elation, hypomania).
Similarly, a decrease in emotional arousal may be desired in
patients engaged in compulsions to reduce anxiety, such as with
OCD. In other instances, the observed change may be unwanted, and
represent a transient or adverse event. In such cases, the goal of
determining the washout period characteristics associated with
therapy delivery according to a plurality of therapy programs would
be to test and identify therapy programs that produce minimal or no
changes in the physiological signal(s).
[0169] A washout period characteristic may be determined for more
than one segment of the washout period. For example, processor 70
may determine the peak amplitude of the physiological signal for
every 5 ms segment of time until the physiological signal returns
to the baseline state. This may enable processor 70 to verify the
return of the amplitude of the physiological signal to the baseline
amplitude is not temporary, i.e., that the physiological signal
does not subsequently increase in amplitude following a return of
the signal to the baseline state. In addition, determining the
washout period characteristic for sequential segments of the
washout period may be useful for determining a trend in the washout
period relatively quickly, e.g., by establishing specific points in
the trend during the washout period.
[0170] In some embodiments, processor 70 may monitor more than one
physiological parameter of patient 14 to determine effects of the
therapy on patient 14. Accordingly, processor 70 may associate
multiple washout period characteristics with each trialed therapy
program, or a weighted washout period characteristics including
respective characteristics from each of a plurality of
physiological signals may be associated with each trialed therapy
program. If multiple physiological signals are monitored during the
pre-stimulation 92, stimulation 94, and post-stimulation periods
96, processor 70 may determine that the washout period has
terminated when all the physiological signals return to their
respective baseline states. Alternatively, processor 70 may
determine that the washout period has terminated when one of the
physiological signals has returned to its baseline state or a
specific subset of the types of physiological signals have returned
to their respective baseline states. The clinician may, for
example, denote one or more of the physiological signals as being
primary signals that control when the washout period has
terminated.
[0171] If processor 70 monitors multiple physiological parameters
of patient 14 to determine a washout period characteristic,
processor 70 may apply weights to the physiological parameters. The
physiological parameters may be weighted based on the relationship
to patient mood state. For example, processor 70 may apply more
weight to a particular physiological parameter based on the
directness of its relationship to a patient mood state, which may
be specific to a patient. Depending on the patient, a mood state
may be characterized by a different set of symptoms. Processor 70
may, for example, generate a weighted summation of the washout
period characteristics and compare the weighted summation to a
threshold to determine when the physiological signals have returned
to a baseline state.
[0172] In some embodiments, processor 70 may apply dynamically
shifting weights to different physiological parameters. For
example, processor 70 may weigh data from different sensors
monitoring different physiological signals based on their
reliability or dynamic response characteristics. Physiological
signals may be subject to interference from factors such as patient
movement, patient breathing, or electrical interference. If the
level of the interference is sufficiently low, the physiological
data signal may still provide accurate data although there may be
some acceptable level of error. In one embodiment, a suitable
filter may be used to apply a variable weight to more than one
physiological parameter according to estimates of the current noise
for signal indicative of the respective physiological
parameter.
[0173] In other cases, different sensing modalities may reflect
different transient responses to therapy stimulation or different
washout period characteristics. For example, EEG activity or heart
rate may reflect relatively short-term trends in behavior of the
physiological parameter of the patient, but may not accurately
measure long-term affects due to variation. In some cases,
long-term patient state (e.g., long term effects of therapy
delivery) may be better reflected in the galvanic skin response and
blood pressure, which may take longer to reach a new equilibrium
following therapy delivery compared to EEG activity or signals
indicative of heart rate. In another embodiment, therefore,
processor 70 may implement an algorithm to establish or apply
weighting factors to different physiological signals from
relatively fast-acting sensors in order to estimate short-term
trends, while for physiological signals indicating longer-term
washout period trends, the weighting may be used to be adjusted to
favor slow-response sensors.
[0174] With the aid of suitable filters like a Kalman filter,
processor 70 may apply less weight to a physiological signal, and,
therefore, the characteristics of the signal during the washout
period, if the signal is subject to a relatively high level of
noise or adjust the relative weighting of sensors to reflect the
dynamic behavior of the sensing modality. In other embodiments,
other types of digital filters may be used to process signals from
sensing module 26 or other sensors of therapy system 10.
[0175] After trialing a plurality of therapy programs and
determining a washout period characteristic for each of the therapy
programs, a clinician, with the aid of clinician programmer 22, may
order the list of therapy programs based on the washout period
characteristics. FIG. 9 is a schematic illustration of clinician
programmer 22, which illustrates a graphical user interface (GUI)
150 presented on display 60 of programmer 22. GUI 150 includes a
list of therapy programs tested during a programming session, which
are designated Program A, Program B, and so forth, along with
associated efficacy ratings 154, washout period characteristics
156, and an overall evaluation metric 157. The efficacy rating and
washout period characteristic may be considered to be evaluation
metrics of the respective therapy program.
[0176] The efficacy rating presented by display 60 in the example
of FIG. 9 is a numerical rating on a scale from 1 to 5, where a
rating of "5" indicates a higher efficacy than a rating of "1."
However, other types of scales are possible, and are not limited to
a numerical scale or a numerical 1-5 scale. Patient 14 may provide
the numerical efficacy ratings, e.g., via clinician programmer 22
or patient programmer 24, in response to therapy delivery according
to each therapy program. In this way, the numerical efficacy
ratings 154 are subjective assessments of the therapeutic efficacy
of a particular therapy program by patient 14. In other
embodiments, processor 70 may automatically rate the efficacy of
the therapy program based on patient responses to various
questions, such as the Beck Depression Inventory, Hamilton Rating
Scale for Depression (HAM-D) or the Montgomery-Asberg Depression
Rating Scale (MADRS). The Beck Depression Inventory and the HAM-D
are both 21-question multiple choice surveys that is filled out by
patient 14, and the MADRS is a ten-item questionnaire. The answers
to the questions may indicate the severity of patient symptoms or
the general patient mood state, and processor 70 may assign an
efficacy rating to the therapy program based on the severity of the
patient symptoms or patient mood state.
[0177] The washout period characteristic shown on display 60 in
FIG. 9 is the duration of the washout period. In other embodiments,
programmer 22 may display other washout period characteristics,
such as the peak amplitude of the physiological signal during the
washout period. In addition, in some embodiments, programmer 22 may
present more than one washout period characteristic for each tested
therapy program.
[0178] In addition to a washout period characteristic, in some
embodiments, the clinician may evaluate the tested therapy programs
based on or a stimulation period characteristic. The stimulation
period characteristic may include a characteristic of the
physiological signal during the stimulation period 94. For example,
the stimulation period characteristic may include the peak, average
or median amplitude of the signal during the stimulation period 94,
a particular trend in the signal waveform, one or more frequency
band characteristics of the signal during the stimulation period 94
or the duration that changes to the signal from the baseline state
were observed. One or more characteristics of a physiological
signal during stimulation period 94 may be suggestive of the
patient's mood state.
[0179] In other embodiments, the clinician may evaluate tested
therapy programs based on other evaluation metrics, such as a mood
indicator rating, an anxiety indicator rating, a patient energy
level rating or a subjective rating of the mood improvement (e.g.,
a mood improvement score) indicated by patient 14 in response to
therapy delivery according to each therapy program. Patient 14 may
directly provide input to clinician programmer 22 regarding these
other evaluation metrics via user interface 74 (FIG. 4) or may
provide input to the clinician or another user, who may then input
the information to clinician programmer 22 or another computing
device. In the case of a mood indicator rating or mood improvement
rating, patient 14 may provide a subjective rating of mood or
improvement of mood, respectively, following therapy delivery by a
therapy program. The rating may be a numerical rating, a sliding
scale or any suitable type of rating system. In the case of an
anxiety disorder, patient 14 may provide a subjective rating of an
anxiety level following therapy delivery by a therapy program. In
the case of MDD, patient 14 may provide a subjective rating of
depression. In some cases, however, patient 14 may have symptoms of
two or more mood disorders, such as MDD and an anxiety disorder,
which may be interrelated.
[0180] A patient energy level rating may also be received from
patient 14 following therapy delivery by a therapy program, e.g.,
via a numerical rating scale. The patient energy level rating may
be useful for evaluating the patient's mood state. For example, in
the case of MDD, a relatively high patient energy level (e.g.,
compared to a baseline energy level prior to delivery of therapy to
patient 14) may indicate the therapy system is improving the
patient's mood state, i.e., is providing at least a minimal amount
of efficacious therapy to patient 14. Processor 70 may associate
the mood indicator rating, anxiety indicator rating, and/or patient
energy level rating with the therapy program.
[0181] Other evaluation metrics may include a rating of the IMD 16
power usage when delivering therapy according to particular therapy
program, which may be associated with the power usage rating in
memory 72 of programmer 22 or a memory of another device. For
example, IMD 16 may consume more energy when generating and
delivering electrical stimulation therapy according to some therapy
programs versus other therapy programs. The energy associated with
each therapy program may be calculated as product of the power
required to generate the stimulation signals defined by the therapy
program and the duration of the stimulation signal. The power
required to generate the stimulation signal may generally be a
product of the voltage and current needed to generate the
stimulation signal. Therefore, an energy associated with a
stimulation signal may be a direct function of voltage, current,
and duration of the stimulation signal.
[0182] In embodiments in which IMD 16 is implanted within patient
14 for chronic therapy delivery, it may be desirable to minimize
power consumption in order to extend the useful life of IMD 16 or
minimize time between recharging of power source 36 (FIG. 2).
Accordingly, the clinician may evaluate the tested therapy programs
based on the respective power usages. The power usage may be, for
example, rated on a numerical scale, where the lower power
consumption therapy programs are provided with a higher energy
efficiency rating. For example, a rating of "5" may be assigned to
therapy programs that require a particular range of power to
generate the stimulation signals defined by the therapy programs, a
rating of "4" may be assigned to therapy programs that require
another range of power for signal generation, where the power range
for the rating of "4" is higher than the power range for the rating
of "5." Other scales for evaluating power usage are
contemplated.
[0183] In some embodiments, a clinician may also evaluate tested
therapy programs based on side effects resulting from therapy
delivery according to the respective therapy programs. Side effect
information that may be collected for each therapy program may
include, for example, the type, duration or severity of the side
effects observed during the stimulation period and/or washout
period, i.e., after stimulation delivery as ceased, as well as the
time during the washout period that the side effects became evident
to patient 14. In some embodiments, patient 14 may provide input
indicating a numerical rating of the side effects, where a higher
numerical rating number indicates a relatively more severe side
effect. Alternatively, patient 14 may select the type of side
effects experienced in response to therapy delivery by a therapy
program from a list provided by programmer 22, and processor 70 may
automatically assign a side effect rating based on the selected
side effects. For example, patient 14 may select a "severe
headache" or "moderate headache" rating from a menu provided by
programmer 22, which processor 70 may automatically associate with
a particular numerical side effect rating.
[0184] Examples of side effects that patient 14 may select from or
rate include, but are not limited to, hypomania effects, euphoria,
perseveration, anxiety (e.g., panic), vague feelings of unease,
subjective feelings of facial flushing, subjective feelings of
increased heart rate, actual facial flushing data (e.g., indicated
by physiological signals during the washout period), actual heart
rate data, paresthesia (e.g., sensations n the face, neck or arms),
and subjective feelings muscular contraction (e.g., sensations in
the face, neck or arms) or actual EMG data reflecting muscular
contraction. The relevant side effects may be determined based on
the patient condition for which therapy system 10 is used to
manage.
[0185] In some cases, an overall evaluation metric 157 may be
generated for each trialed therapy program, where the specific
evaluation metrics, such as the efficacy rating, washout period
characteristic, stimulation period characteristic, mood indicator
rating, an anxiety indicator rating, a patient energy level rating,
and/or power consumption or efficiency rating, are weighted
according to their relative importance to the therapy program
evaluation. For example, the clinician may determine that the
washout period characteristic should have twice the weight as the
efficacy rating, due to the subject nature of the efficacy rating
and the relatively objective nature of the washout period
characteristic. As another example, the clinician may select the
one or more therapy programs having the greatest improvement in
patient mood state, minimal or no side effects, and optimal battery
life for chronic therapy delivery to patient 14.
[0186] In the embodiment shown in FIG. 9, each washout period
characteristic is given a score on a scale from 1 to 5, where a
score of "1" indicates a washout period duration of between about 0
seconds (s) and about 30 s, a score of "2" indicates a washout
period duration of between about 30 s to about 2 minutes (min), a
score of about "3" indicates a washout period duration between
about 2 min to about 4 min, a score of about "4" indicates a
washout period duration between about 4 min to about 6 min, and a
score of about "5" indicates a washout period duration between of
about 6 min or higher. Some physiological effects, such as facial
flushing, may take a relatively long time (on the duration of
minutes) to return to a baseline state. These washout period scores
may then be weighted with the efficacy rating to arrive at the
overall metric. For example, with respect to Program A, the washout
period duration is about 5 minutes, thus, the score is 4. If the
washout period characteristic has twice the weight as the efficacy
rating, the overall metric would equal approximately 5.5 (i.e.,
(washout period score*2+efficacy rating)/2).
[0187] Processor 70 of clinician programmer 22 may receive input
from the clinician or another user selecting one of the evaluation
metric types with which to order the list of therapy programs. For
example, display 60 may be a touch screen display, and the
clinician may select efficacy rating box 154, washout period
characteristic box 156 or weighted metric box 157, and processor 70
may order the list of therapy programs according to evaluation
metric associated with the selected text box. In some cases, the
clinician may wish to maximize the duration of the washout period,
e.g., to maximize the energy efficiency of IMD 16. The clinician
may determine which therapy program resulted in the longest washout
period duration by ordering the list of therapy programs according
to the washout period duration or the overall metric 157, as shown
in FIG. 9.
[0188] Ordering the list of therapy programs according to a
user-chosen criteria enables the clinician to quickly identify the
therapy programs that exhibited the longest washout period
duration, as well as to identify the respective efficacy rating for
the therapy programs. In contrast, without the automatic ordering
of the therapy programs list according a user-chosen criteria, the
clinician must typically manually sort through the data in order to
identify the therapy program with the desired evaluation metric
values. In other embodiments, the clinician may wish to decrease
the washout period.
[0189] In the embodiment shown in FIG. 9, the therapy programs are
ordered according to the associated washout period characteristics.
In the example shown in FIG. 9, Programs A and B both exhibited the
longest relative washout period duration. However, Program B is
associated with a higher efficacy rating (5) than Program A (rating
of 3). In addition, Program B has a higher overall metric value
than Program A, due to the higher efficacy rating. Accordingly, the
clinician may choose to implement Program B for chronic therapy
delivery or to use Program B to generate further therapy programs
for testing.
[0190] In some cases, the clinician may further evaluate Program B,
e.g., by rating the efficacy of Program B based on patient
responses to various questions, such as the Beck Depression
Inventory, Hamilton Rating Scale for Depression (HAM-D) or the
Montgomery-Asberg Depression Rating Scale (MADRS). In some cases,
processor 70 may prompt patient 14 to answer the questions after
therapy is delivered to patient according to Program B. The
questions may be presented to patient 14 via display 60 of
clinician programmer 22, or by another electronic form or paper
form and the answers may be inputted into clinician programmer 22.
The patient's answers to the questions may be useful for confirming
the usefulness of Program B, as well as other selected therapy
programs.
[0191] In some cases, processor 70 of clinician programmer 22 may
automatically determine more than one washout period characteristic
for each therapy program. Thus, in some embodiments, GUI 150 may
present more a list of therapy programs along with two or more
types of associated washout period characteristics. The clinician
may order the list according to any one of the washout period
characteristics. In addition, the clinician may order the list
according to an overall metric that applies different weights to
two or more of evaluation metrics, which may include two or more
washout period characteristics (e.g., washout period duration and
peak amplitude).
[0192] Compared to the respective efficacy ratings 154 or other
subjective evaluation metrics received from patient 14 (e.g.,
ratings as to severity of side effects), a washout period
characteristic and stimulation period characteristic may provide a
relatively objective metric with which to evaluate therapy
programs. The washout period and stimulation period characteristics
are determined based on a monitored physiological signal of patient
14 rather than the subjective input from patient 14. Accordingly,
the washout period and stimulation period characteristics may also
be useful for evaluating therapy programs, e.g., based on a
consistency between the patient's subjective input and information
determined based on the stimulation and/or washout period
characteristics.
[0193] As one example, if patient 14 provides an efficacy rating of
"3" for Programs A and D, as shown in FIG. 9, but the washout
period characteristics are different, the clinician may conclude
that the Programs A and D are effective, but not as effective as
Therapy Program B, which may be associated with a consistency
indication that indicates the patient input regarding a mood state
was consistent with a mood state determined based on a washout or
stimulation period characteristic. In addition, the clinician may
conclude that the washout period characteristic or stimulation
period characteristic is useful for differentiating between the
effects of Programs A and D. Similar efficacy ratings for two or
more therapy programs may indicate that the patient efficacy rating
scale is not fine enough. Thus, the washout period characteristic
(or the stimulation period characteristic) may be useful for
determining between subtle differences in the effects of different
therapy programs on patient 14.
[0194] In some cases, the patient input may be entitled to less
weight than the physiological signal. That is, because the washout
period and stimulation period characteristics are determined based
on a monitored physiological signal of patient 14 rather than the
subjective input from patient 14, the washout period and
stimulation period characteristics may also be useful for assessing
the consistency of the patient's subjective input for other
evaluation metrics and assessing the validity of the patient's
input. If, for example, patient 14 provides an efficacy rating of
"3" for Programs A and D, as shown in FIG. 9, but the washout
period characteristics are different, the clinician may conclude
that the patient's efficacy rating is invalid or entitled to less
weight than the washout period characteristic. Thus, the clinician
may conclude that the washout period characteristic is more useful
for differentiating between the effects of Programs A and D.
[0195] As another example, the objective nature of the washout
period and stimulation period characteristics may be useful for
diagnosing a placebo effect from the stimulation therapy. For
example, if patient 14 provides an efficacy rating of "5" for all
tested therapy programs, but the washout period characteristics or
stimulation period characteristics differ greatly between the
tested therapy programs, the clinician may determine that minimal
to no stimulation therapy is necessary to manage the patient's
psychiatric disorder.
[0196] Clinician programmer 22 also includes housing 152, power
button 158, contrast buttons 160A, 160B, control pad 162 with
directional buttons 164A, 164B, 164C, and 164D, increase button
166, and decrease button 168. Housing 152 may substantially enclose
the components of programmer 22, such as processor 70 and memory
72. A user may depress power button 158 to turn programmer 22 on or
off. Programmer 22 may include safety features to prevent
programmer 22 from shutting down during a telemetry session with
IMD 16 or another device in order to prevent the loss of
transmitted data or the stalling of normal operation.
Alternatively, programmer 22 and IMD 16 may include instructions
for handling possible unplanned telemetry interruption, such as
battery failure or inadvertent device shutdown.
[0197] As previously indicated with respect to FIG. 4, display 60
may be a liquid crystal display (LCD), touch screen display, or
another type of monochrome or color display capable of presenting
information to a user, e.g., a clinician. Contrast buttons 160A,
160B may be used to control the contrast of display 60. In addition
to displaying a list of trialed therapy programs and associated
evaluation metrics, processor 70 of clinician programmer 22 may
also present information regarding the type of IMD 16, operational
status of IMD 16, patient data, and operational status of clinician
programmer 22 on display 60. Control pad 162 allows the user to
navigate through items presented on display 60. For example, the
clinician may press control pad 120 on any of arrows 164A-164D in
order to move between items presented on display 60 or move to
another screen not currently shown by display 60. For example, the
clinician may depress or otherwise activate arrows 164A, 164C to
navigate between screens of GUI 150, and depress or otherwise
activate arrows 164B, 164D to scroll through the therapy programs
presented by GUI 150. The clinician may press the center portion of
control pad 162 in order to select any highlighted element in GUI
150. For example, the clinician may scroll to and select "PROGRAM
B," which is shown to be highlighted in FIG. 9, in order to receive
more information about Program B, such as the stimulation parameter
values defined by Program B. In other embodiments, scroll bars, a
touch pad, scroll wheel, individual buttons, a stylus (in
combination with a touch screen display 60) or a joystick may
perform the complete or partial function of control pad 162.
[0198] Increase button 166 and decrease button 168 provide input
mechanisms for a user, such as clinician or patient 14. In general,
depressing decrease button 168 one or more times may decrease the
value of a highlighted therapy parameter and depressing increase
button 166 one or more times may increase the value of a
highlighted therapy parameter. While buttons 166, 168 may be used
to control the value of any therapy parameter, the user may also
utilize buttons 166, 168 to select or generate particular programs
for testing during a therapy programming session. In addition,
patient 14, the clinician or another user may utilize control pad
120, buttons 166, 168 or display 60 in embodiments in which display
60 comprises a touch screen to input information related to the
efficacy of a therapy program or other evaluation metrics. Further,
the clinician or another user may utilize control pad 162, buttons
166, 168 or display 60 in embodiments in which display 60 comprises
a touch screen in order to input information related to a washout
period characteristic. Alternatively, processor 70 of programmer 22
may automatically determine the washout period characteristics
based on physiological parameter signals received from sensing
module 26 (FIG. 1).
[0199] Clinician programmer 22 may take other shapes or sizes not
described herein. For example, programmer 22 may take the form of a
clam-shell shape, similar to cellular phone designs. In any shape,
programmer 22 may be capable of performing the requirements
described herein. Furthermore, in other embodiments, the buttons of
programmer 22 may perform different functions than the functions
provided in FIG. 9 as an example. In addition, other embodiments of
programmer 22 may include different button layouts or number of
buttons. For example, display 60 may be a touch screen that
incorporates all user interface and user input mechanism
functionality.
[0200] FIG. 10 is a flow diagram illustrating an embodiment of a
technique for ordering a list of therapy programs according to a
washout period characteristic. With the aid of clinician programmer
22 or another computing device, a clinician may deliver electrical
stimulation to patient 14 according to a plurality of therapy
programs during a trial stimulation session (170). As previously
indicated, during a trial stimulation session, stimulation may be
delivered to patient 14 according to each therapy program for a
sufficient period of time to determine the effects, if any, the
therapy has on patient 14. For each trialed therapy program, the
clinician may determine a washout period characteristic (172). For
example, processor 70 of programmer 22 may automatically determine
the washout period characteristics during the trial therapy
sessions. In addition, other evaluation metrics may be generated
for each therapy program, such as an efficacy rating (e.g., a
numerical efficacy rating or a pain map) or different thresholds
for each therapy program (e.g., a perception threshold).
[0201] In some cases, the clinician may determine a weighted
evaluation metric (i.e., an overall metric) for each trialed
therapy program. As previously indicated, two or more evaluation
metrics (e.g., efficacy rating or washout period characteristic)
may be combined into a composite metric by applying weights to the
evaluation metrics based on their relative importance to the
evaluation of the therapy programs, where the evaluation metrics
may be weighted the same or differently. The clinician may order
the list of therapy programs based on an evaluation metric that
considers the washout period characteristic (174). For example, the
clinician may order the list of therapy programs with the aid of
GUI 150 of clinician programmer 22 (FIG. 9) according to the
washout period characteristic or an overall evaluation metric. In
this way, the clinician may evaluate the trialed therapy programs
based on the washout period characteristic in a relatively quick
manner. If more than one washout period characteristic is
determined for each therapy program, the clinician may order the
list of trialed therapy programs according to one of the
characteristics or according to an evaluation metric that considers
two or more of the washout period characteristics.
[0202] When titrating DBS parameter values to determine an
efficacious range of therapy parameter values for managing a mood
disorder of patient 14, changes in mood state during stimulation
period 94 (FIGS. 5A-5E) as well as during the post-stimulation
period 96 (FIGS. 5A-5E) may be desirable. For example, changes to
the patient's mood state may indicate the patient's response to
therapy delivery according to a particular therapy program.
Associating a patient mood state with a washout period
characteristic, and, in some cases, a stimulation period
characteristic ("mood state classification") may be useful for
screening therapy programs, e.g., to help identify a target change
in a physiological signal during a washout period that indicates a
beneficial change to the patient's psychiatric disorder. Similarly,
a washout period characteristic may also be useful for avoiding
stimulation parameter values that result in adverse events. For
example, after delivering therapy to patient 14 according to a
therapy program during a trial session, the clinician may identify
a target change in a physiological signal during the washout period
that is associated with a negative mood state (e.g., a depressed
state, hypomanic state or manic state). In response, the clinician
may test another therapy program or modify at least one therapy
parameter value of the tested therapy program.
[0203] In addition, as described in further detail below,
associating a washout period characteristic with a patient mood
state may be useful for a closed-loop therapy system. For example,
if a certain characteristic of a physiological signal during the
washout period is associated with an improvement in a MDD of
patient 14, a closed-loop therapy system may deliver therapy,
monitor the physiological signal, and continue delivering therapy
until the characteristic of the physiological signal is observed
following therapy delivery.
[0204] FIG. 11 is a flow diagram illustrating an example technique
for associating different patient mood states with one or more
washout period characteristics. In this way, at a later time, a
washout period characteristic resulting from therapy delivery may
be used to determine a patient mood state. As with the previous
techniques, although the technique shown in FIG. 11 is described as
being performed by processor 70 of clinician programmer 22, in
other embodiments, processor 40 of patient programmer 24 or a
processor of another computing device may associate different
patient mood states with one or more washout period characteristics
in accordance with the technique shown in FIG. 11.
[0205] Processor 70 of clinician programmer 22 may control IMD 16
to deliver therapy to patient 14 according to a therapy program
(120) using any suitable technique, such as the ones described
above with respect to FIG. 7A. Processor 70 may receive a signal
from sensor 26 indicating activity of a physiological parameter of
patient 14, such as the patient's respiratory rate, heart rate or
galvanic skin response. Based on the physiological signal from
sensor 26, processor 70 may automatically determine a
characteristic of a washout period associated with the therapy
program (180). For example, processor 70 may use the technique
described with respect to FIG. 8 to determine the washout period
characteristic. Processor 70 may associated the washout period
characteristic with the therapy program (182), and record the
washout period characteristic in memory 72 (FIG. 4) of clinician
programmer 22.
[0206] Processor 70 may receive input from patient 14 indicating a
mood state during the post-stimulation period, and, in some cases,
the stimulation period (184). The patient 14 may indicate a mood
state felt by patient 12 in response to therapy delivery according
to the therapy program. The mood state may be the mood state that
is first observed during the stimulation period and substantially
persists throughout a washout period, which follows the stimulation
period. In other examples, the mood state associated with the
therapy program may be first observed during the post-stimulation
period. In one embodiment, patient 14 provides input indicating a
mood state by interacting with user input mechanism 56 of user
interface 44 of patient programmer 24. As another example, patient
14 may provide input indicating a mood state by interacting with
user input mechanism 56 of user interface 74 of clinician
programmer 22 either directly or indirectly, e.g., via another user
than inputs the information into clinician programmer 22.
[0207] Patient 14 may indicate a mood state using any suitable
technique. For example, patient 14 may select a mood state from a
predefined list of mood states (e.g., moderate anxiety, severe
anxiety, lack of anxiety, in the case of an anxiety disorder),
manually input a mood state, select a numerical rating of the
severity of a specific mood state (e.g., a numerical range of 1
through 5, where a rating of "5" indicates patient 14 experienced a
severe depressive state, while a rating of "1" indicates patient 14
was in a relatively non-depressed state compared to a depressive
state). Other techniques for receiving input regarding a mood state
of patient 14 are contemplated.
[0208] Processor 70 may associate the indicated mood state with the
washout period characteristic (186) and store the data in memory 72
of programmer 22 or a memory of another device, such as IMD 16 or
patient programmer 24. In some cases, upon request by a user,
processor 70 may present a list, table or other data format
illustrating the washout period characteristics and associated mood
states via display 60. For example, if the washout period
characteristic includes a peak or average value of the waveform
amplitude of the physiological signal during the washout period,
processor 70 may present a list of a plurality of mood states and
associated physiological signal amplitude values. As another
example, if the washout period characteristic includes a trend in
the physiological signal waveform during the washout period,
processor 70 may present a list of mood states and provide links to
a visual representation of the waveform trend.
[0209] After associating washout period characteristics with mood
states for one or more patients, a clinician may generate a mood
state probability for each washout period characteristic. In some
cases, the washout period characteristic may not provide a direct
link to patient mood and may be a surrogate marker that is
suggestive of the patient mood state, rather than symptomatic.
Thus, the association between mood states and washout period
characteristics may be somewhat inaccurate and imprecise.
Furthermore, the patient input regarding the mood state may be
inaccurate or inconsistent between therapy programs having similar
washout period characteristics. Accordingly, it may be desirable
for the clinician to confirm that a mood state is associated with a
particular washout period characteristic by recording the patient's
mood state for multiple trials of one or more therapy programs that
result in the washout period profile. That is, processor 70 may
determine that a washout period characteristic is associated with a
patient mood state only after the patient indicates the same mood
state for the same washout period characteristic a minimum number
of times, regardless of whether the washout period characteristic
is generated by the same therapy program. Different therapy
programs may result in the same washout period characteristic.
[0210] In some embodiments, rather than directly associating a
patient mood state with a washout period characteristic, processor
70 may assign a probability of the mood state with the washout
period characteristic. For example, for a particular washout period
characteristic, processor 70 may determine that 85% of the time the
washout period characteristic was observed, patient 14 indicated a
non-depressive mood state. The washout period characteristics may
be associated with a patient mood state based on testing therapy
programs on a single patient or more than one patient.
[0211] Mood state classification based on washout period
characteristics may be beneficial for screening therapy programs.
After establishing a library (or catalog or any data structure) of
washout period characteristics and associated mood states or mood
state probabilities, a clinician may evaluate the efficacy of one
or more therapy programs by associating the therapy program with a
mood state or mood state probability based on the washout period
characteristic associated with the therapy program. The library of
period characteristics and associated mood states or mood state
probabilities may be specific to patient 14 (i.e., generated based
on information from patient 14) or may be more general, e.g., based
on information from more than one patient.
[0212] In some embodiments, processor 70 may also determine a
stimulation period characteristic, receive input from patient 14
indicating a mood state, and associate the stimulation period
characteristic with the patient mood state using a technique
similar to that shown in FIG. 11.
[0213] Although FIG. 11 illustrates associating a mood state with a
washout period characteristic based on data from a single patient,
in some embodiments, mood states may be associated with washout
period characteristics based on data from more than one patient.
Thus, in some cases, mood state information and washout period
characteristics from a cross-section of patients (e.g., a class of
patients having similar conditions) may be used to support an
assumed correlation between a mood state and a washout period
characteristic.
[0214] FIG. 12 is a flow diagram illustrating an example technique
for associating a therapy program with a patient mood state based
on the washout period characteristic associated with the therapy
program. Just as with the technique shown in FIG. 11, processor 70
may deliver therapy to patient 14 according to a therapy program
(120) and determine a washout period characteristic of the therapy
program (180). If the washout period characteristic comprises a
washout period duration or physiological signal amplitude,
processor 70 may compare the washout period characteristic to a
threshold value (188). The threshold value may be stored in memory
72 of clinician programmer 22 or a memory of another device. The
threshold value may indicate the presence of a particular patient
state during the washout period, and may be established using any
suitable technique that associates a washout period characteristic
with a patient mood state, such as the technique described with
respect to FIG. 11.
[0215] In some embodiments, processor 70 may compare the washout
period characteristic to one or more threshold values, which may
each be associated with a different patient mood state. FIG. 13
illustrates a data structure that associates a plurality of patient
mood states with threshold amplitude values. The threshold values
are listed in terms of a voltage amplitude change relative to a
baseline amplitude value, which may be established during the
pre-stimulation period 92 (FIGS. 5A-5E), prior to the delivery of
stimulation according to the therapy program. As previously
discussed, the baseline amplitude value may include a peak voltage
or current amplitude of the signal during the pre-stimulation
period 92, a mean, median or average value of the physiological
signal amplitude during the pre-stimulation period 92, or other
values based on the amplitude of the physiological signal amplitude
during the pre-stimulation period 92.
[0216] While a baseline amplitude value of the physiological signal
may differ between patients, it may be found that for a plurality
of patients, a change in the physiological signal amplitude is
associated with a particular patient mood state. Accordingly, the
threshold value may be stated in terms of the sum of the baseline
amplitude value and the absolute change in the physiological signal
amplitude. In other embodiments, the threshold value may be merely
stated in terms of the amplitude change in the physiological
signal, and processor 70 may determine the washout period
characteristic to be the change in the physiological signal
amplitude relative to the baseline amplitude value.
[0217] Processor 70 may compare the washout period characteristic
to the threshold values shown in FIG. 13 in order to determine
whether patient 14 is in a non-depressed mood state, moderately
depressed mood state or a severely depressed mood state. For
example, if the amplitude value of the washout period
characteristic exceeds (or, in some embodiments, is greater than or
equal to) the threshold value associated with the non-depressed
mood state, processor 70 may conclude that patient 14 is in a
non-depressed mood state. On the other hand, if the amplitude value
of the washout period characteristic does not exceed (or, in some
embodiments, is less than or equal to) the threshold value
associated with the non-depressive mood state, processor 70 may
conclude that patient 14 was not in a non-depressed mood state
following therapy delivery according to the therapy program.
[0218] Processor 70 may then compare the amplitude value of the
washout period characteristic to the threshold value associated
with the moderate depression mood state. If the amplitude value of
the washout period characteristic exceeds (or, in some embodiments,
is greater than or equal to) the threshold value associated with
the moderate depression mood state, processor 70 may conclude that
patient 14 was in a moderately depressed mood state following
therapy delivery according to the therapy program. On the other
hand, if the amplitude value of the washout period characteristic
does not exceed (or, in some embodiments, is less than or equal to)
the threshold value associated with the moderate depression mood
state, processor 70 may conclude that patient 14 was not moderately
depressed following therapy delivery according to the therapy
program. Processor 70 may then conclude that patient 14 was in a
severely depressed mood state following therapy delivery according
to the therapy program. In some cases, processor 70 may compare the
amplitude value of the washout period characteristic to the
threshold value associated with the severe depression mood state in
order to verify that patient 14 was in a severely depressed mood
state following therapy delivery according to the therapy
program.
[0219] Processor 70 may employ a similar technique to compare a
washout period characteristic with multiple thresholds other than
amplitude thresholds. While a voltage amplitude is shown in FIG.
13, in other embodiments, the baseline amplitude may be a current
amplitude. In addition, in other embodiments, other mood state
characteristics may be associated with the mood states. For
example, the threshold value may be a washout period duration
provided in terms of seconds or milliseconds. Furthermore, the
threshold values associated with the patient mood state in FIG. 13
are for purposes of illustration only. Other threshold values for
determining a patient mood state are contemplated.
[0220] Returning now to the flow diagram shown in FIG. 12, if
processor 70 determines that the washout period characteristic is
not greater than or equal to one or more threshold values (190),
processor 70 may not associate the therapy program with a
particular mood state. On the other hand, if processor 70
determines that the washout period characteristic is greater than
or equal to one or more threshold values (190), processor 70 may
associate the determined mood state with the therapy program (192).
Processor 70 may determine the mood states for a plurality of
therapy programs and compare the efficacy of the therapy programs
based on the associated mood states.
[0221] In some cases, a washout period characteristic may be a
trend in the physiological signal during the post-stimulation
period. FIG. 14 is a flow diagram illustrating an example technique
for associating a therapy program with a patient mood state based
on a comparison between a washout period characteristic and a
template, which may be stored in memory 72 of clinician programmer
22. Processor 70 may control the delivery of therapy to patient 14
according to a therapy program (120). During the washout period, if
any, following the therapy delivery, processor 70 may monitor a
pattern of the physiological signal waveform (194) and compare the
pattern to a template (196).
[0222] In one embodiment, processor 70 performs a temporal
correlation between the physiological signal waveform during the
washout period and the template. Processor 70 may sample the
physiological signal with a sliding window and compare the sampled
waveform with a stored template waveform. For example, processor 70
may perform a correlation analysis by moving a window along a
digitized plot of the amplitude waveform of physiological signal at
regular intervals, such as between about 1 ms to about 10 ms
intervals, to define a sample of the physiological signal during
the washout period. The sample window is slid along the plot until
a correlation is detected between the waveform of the template and
the waveform of the sample of the physiological signal defined by
the window, or until the end of the washout period (e.g., when the
physiological signal returns to a baseline state). By moving the
window at regular time intervals, multiple sample periods are
defined. The correlation may be detected by, for example, matching
multiple points between the template waveform and the waveform of
the plot of the physiological signal over time, or by applying any
suitable mathematical correlation algorithm between the sample in
the sampling window and a corresponding set of samples stored in
the template waveform.
[0223] If the pattern of the physiological signal waveform does not
match the template (196), processor 70 may determine that there is
no patient state associated with the washout period characteristic.
In some cases, processor 70 may prompt patient 14 to input
information relating to the patient mood state following the
therapy delivery, e.g., by initiating a communication session with
patient 14 via display 60, and associate the patient indicated mood
state with the washout period characteristic.
[0224] If the pattern of the physiological signal waveform
substantially matches (e.g., within a particular percentage, such
as 90% to about 100% match) the template (196), processor 70 may
associate the patient mood state with the therapy program (192). In
some embodiments, processor 70 may compare the physiological signal
waveform to a plurality of templates, which are each associated
with a different patient state.
[0225] In some cases, a washout period characteristic may be a
frequency band characteristic of the physiological signal during
the post-stimulation period, such as an energy level in a
particular frequency band or a ratio in energy levels between
different frequency bands. FIG. 15 is a flow diagram illustrating
an example technique for associating a therapy program with a
patient state based on a comparison between a washout period
characteristic and a threshold energy level of a frequency band,
which may be stored in memory 72 of clinician programmer 22 or a
memory of another device. Processor 70 may control the delivery of
therapy to patient 14 according to a therapy program (120). During
the washout period, if any, following the therapy delivery
according to the therapy program, processor 70 may monitor a
physiological signal (194) and compare the energy level of the
physiological signal within one or more frequency bands to a
threshold value (198).
[0226] Either sensing module 26 or processor 70 may tune the
physiological signal to a particular frequency band that is
indicative of the patient's mood state. For example, in one
embodiment, processor 70 tunes the physiological signal to the
alpha band (e.g., about 5 Hz to about 10 Hz). The energy level of
the physiological signal within the selected frequency band may be
considered to be the washout period characteristic in some
embodiments. Processor 70 may compare energy level within the
particular frequency band during the washout period to a stored
value to determine the patient mood state resulting from therapy
delivery according to the therapy program. In another embodiment,
processor 70 may compare the ratio of power levels within two or
more frequency bands to a stored value in order to determine the
patient mood state.
[0227] If the energy level of the physiological signal during the
washout period is not greater than or equal to the threshold value
(198), processor 70 may determine that there is no patient state
associated with the washout period characteristic. In some cases,
processor 70 may prompt patient 14 to input information relating to
the patient mood state following the therapy delivery, e.g., by
initiating a communication session with patient 14 via display 60,
and associate the patient indicated mood state with the washout
period characteristic. If the energy level of the physiological
signal during the washout period is greater than or equal to the
threshold value (198), processor 70 may associate the patient mood
state with the therapy program (192). In some embodiments,
processor 70 may compare the energy level or ratio of energy levels
of the physiological signal to a plurality of threshold values,
which are each associated with a different patient mood state.
[0228] Although the technique shown in FIG. 15 associates a patient
mood state with a therapy program if the energy level of the
physiological signal within one or more frequency bands is greater
than or equal to a threshold value, in other embodiments, processor
70 may determine the presence of the mood state if the energy level
of the physiological signal within one or more frequency bands is
greater than a threshold value, less than the threshold value, or
less than or equal to the threshold value.
[0229] In another embodiment, the correlation of changes of power
between frequency bands may be compared to a stored value to
determine whether the physiological signal indicates patient 14 is
in a particular mood state. This correlation of changes in power of
different frequency bands may be implemented into an algorithm that
helps processor 70 eliminate false positives of a patient mood
state by relying on energy levels within more than one frequency
band.
[0230] In some embodiments, processor 70 may also associate a
therapy program with a patient mood state based on a stimulation
period characteristic with a technique similar to that shown in
FIGS. 12, 14, 15. The association between a therapy program and a
stimulation period characteristic may be used for similar purposes
as the association between a therapy program and a washout period
characteristic. The patient mood state may be associated with a
stimulation period characteristic in any suitable way, such as with
a technique similar to that shown in FIG. 11.
[0231] The techniques shown in FIGS. 12, 14, and 15 may be used to
determine the efficacy of a therapy program or to determine the
relatively efficacy of a plurality of therapy programs based on a
patient mood state following delivery of therapy according to the
therapy programs. In some cases, mood state classification may also
be useful for modifying at least one therapy parameter value of a
therapy program. For example, after identifying a target change in
a physiological signal during the washout period that is associated
with a negative mood state, e.g., using the techniques shown in
FIG. 12, 14 or 15, a clinician may test another therapy program or
modify at least one therapy parameter value of the tested therapy
program. The clinician may adjust the at least one therapy
parameter value in order to generate a therapy program that
improves the patient's mood state from the patient's baseline state
and/or from the patient's mood state following therapy delivery
according to the tested therapy program.
[0232] FIG. 16 is a flow diagram illustrating an embodiment of a
technique for adjusting a therapy program based on a patient mood
state generated in response to therapy delivery according to the
therapy program. Processor 70 may control therapy delivery to
patient 14 according to a therapy program (120) and determine a
washout period characteristic associated with the therapy program
(180), e.g., using the technique described above with respect to
FIG. 8. Processor 70 may determine a patient mood state based on
the washout period characteristic (200), e.g., using the techniques
described with respect to FIGS. 12, 14, and 15.
[0233] Processor 70 may determine whether the determined patient
mood state is a positive mood state (202). For example, if patient
14 has a MDD and therapy system 10 provides therapy to improve the
patient's depressive mood, a positive mood state would be a
relatively less depressed mood state than the patient's baseline
mood state. Alternatively, the positive mood state may be an
objectively positive mood state, rather than a relatively positive
mood state. For example, although a moderately depressed mood state
may be an improvement on the patient's baseline mood state, the
clinician may determine that the moderately depressed mood state is
not a positive mood state, but rather, a substantially
non-depressed mood state is a positive mood state.
[0234] If processor 70 determines that the washout period
characteristic indicates a positive mood state (202), processor 70
may consider the therapy program efficacious and may not take any
action to modify the therapy program. On the other hand, if
processor 70 determines that the washout period characteristic does
not indicate a positive mood state (202), processor 70 may adjust
at least one therapy parameter value of the therapy program based
on the determined mood state (204). Processor 70 may modify the
therapy program to help improve the patient mood state resulting
from therapy delivery according to the therapy program, e.g., to
make the therapy delivery more efficacious. Processor 70 may modify
the therapy program using any suitable technique, such as the
tree-based technique or the genetic algorithm technique described
above with respect to FIG. 16. In some cases, the technique shown
in FIG. 16 may be used in a closed-loop therapy system to modify a
therapy program during chronic therapy delivery, e.g., after a
trial session in which efficacious therapy parameter values are
titrated.
[0235] Many therapy systems 10 used to provide stimulation therapy
to patient 14 to manage a psychiatric disorder provide
substantially continuous delivery of stimulation to patient 14. One
drawback with the continuous stimulation approach is the
inefficient use of power. For example, with continuous delivery,
therapy may be provided to patient 14 even though patient 14 does
not need the therapy. Therapy may be unnecessary or undesired when
patient 14 is in a positive mood state. A positive mood state may
be a relatively positive mood state, such as an improvement on the
patient's baseline mood state (e.g., a moderately depressed mood
state compared to a baseline state of severe depression), or may be
an objectively positive mood state, such as a non-depressed or
non-anxious mood state. Accordingly, a negative mood state may be a
relatively negative mood state, such as mood state worse than the
patient's baseline mood state (e.g., a severely depressed mood
state compared to a baseline state of moderate depression), or may
be an objectively negative mood state, such as a state of severe
depression or severe anxiousness.
[0236] Information associating a patient mood state with a washout
period characteristic may be useful for controlling the delivery of
therapy. In one embodiment, a physiological parameter of patient 14
may be monitored and a response of the physiological parameter to
the delivery of psychiatric disorder therapy may be used to cycle
IMD 16 between an active delivery state ("on" state) and a sleep or
off state, during which IMD 16 does not deliver therapy to patient
14. The physiological parameter of the patient may, therefore, be
monitored to provide "on demand" therapy to patient 14. In
particular, a patient mood state may be determined based on the
physiological parameter, such as by determining a patient mood
state associated with a washout period characteristic that
indicates a physiological parameter value or trend. The therapy
delivery may then be controlled based on the determined patient
mood state.
[0237] The physiological parameter of patient 14 that is monitored
for the closed-loop control of therapy system 10 may be a parameter
that is indicative of the patient's mood state, such as a heart
rate, respiratory rate, electrodermal activity, thermal activity or
muscle activity (e.g., facial EMG). A physiological parameter
characteristic, such as a trend or amplitude value of a
physiological signal measuring the activity of the physiological
parameter, may be associated with a patient mood state using any
suitable technique, such as the one described above with respect to
FIG. 11. The information associating a patient mood state with a
physiological parameter characteristic may be based specific to
patient 14 or may be general to two more patients.
[0238] The techniques shown in FIGS. 12, 14, and 15 may also be
used to determine the efficacy of a therapy program or to determine
the relatively efficacy of a plurality of therapy programs based on
a patient mood state during delivery of therapy according to the
therapy programs using the technique described with respect to FIG.
16. However, rather than determining a washout period
characteristic, processor 70 or another processor may determine a
characteristic of a physiological signal during a stimulation
period, and determine a patient mood state based on the stimulation
period characteristic.
[0239] FIG. 17 is a flow diagram illustrating an embodiment of a
technique for controlling the delivery of therapy to patient 14
based on a patient mood state. While processor 34 (FIG. 2) of IMD
16 is primarily referred to throughout the description of FIGS. 17
and 18, in other embodiments, a processor of another device, such
as clinician programmer 22 or patient programmer 24 may perform any
part of the technique shown in FIGS. 17 and 18. Processor 34 may
control therapy module 32 to deliver therapy to patient 14 (210)
according to one or more therapy programs that have been determined
to provide efficacious therapy to patient 14. The therapy program
may be selected using any of the techniques above, such as based a
technique that evaluates therapy programs based on a washout period
characteristic alone or in combination with other evaluation
metrics.
[0240] Processor 34 may monitor a physiological parameter of
patient and determine a mood state of patient based on the
monitored parameter (212) as therapy is actively delivered, e.g.,
as electrical stimulation signals are delivered to patient 14. For
example, processor 34 may monitor a physiological parameter of
patient 14, e.g., via signals provided by sensor 26 (FIG. 1) or
signals provided by sensors on leads 20 or on a housing of IMD 16.
The physiological parameter may be at least one of a respiratory
rate, electrodermal activity, thermal activity or muscle activity
of patient 14, which may be a surrogate marker for a mood state of
patient 14. In addition, in some examples, the physiological
parameter may include a brain signal (e.g., an EEG or ECoG) in
addition to the respiratory rate, electrodermal activity, thermal
activity or muscle activity.
[0241] Processor 34 may compare the physiological signal to one or
more thresholds or templates in order to determine a mood state,
e.g., using techniques similar to those described with respect to
FIGS. 12, 14, and 15. Processor 34 may determine the patient mood
state at periodic intervals, such as about every one second to
every one minute or more. Processor 34 may determine a specific
mood state of patient 14, such as a severely depressed mood state,
moderately depressed mood state, and the like. Processor 34 may
determine the mood state from among a plurality of stored mood
states, where each mood state is associated with a physiological
signal characteristic in memory 35 of IMD 16 or a memory of another
device.
[0242] If processor 34 detects a negative mood state (214),
processor 34 may continue delivering therapy to patient (210).
Processor 34 may detect a negative mood state, e.g., by comparing
the determined mood state with a baseline mood state, which may be
stored in memory 42. As previously indicated, the baseline mood
state may be a mood state of patient 14 prior to any therapy
delivery by therapy system 10. Alternatively, processor 34 may
automatically determine that predetermined mood states are
negative, regardless of the patient's baseline mood state. For
example, processor 34 may determine the mood state of patient 14
indicated by the sensed physiological signal by comparing a
characteristic of the sensed signal to a plurality of stored
templates or threshold values that are each associated with
different mood states. If the determined mood state is indicated as
being a negative mood state in memory 35, processor 34 may control
therapy module 32 to continue delivery therapy to patient 14.
[0243] In some embodiments, processor 34 may also modify the
therapy program based on the detected mood state. For example,
processor 34 may modify the therapy program if processor 34
determines that the current therapy program is insufficiently
efficacious, e.g., based on past detection of negative mood states.
In one embodiment, processor 34 may track the number of times a
negative mood state is detected during the delivery of therapy
according to the therapy program and compare the total number of
negative mood states or a number of mood states within a particular
subset of time to a threshold value.
[0244] As another example, processor 34 may determine that the
current therapy program is insufficiently efficacious and modify
the therapy program if processor 34 determines that the patient
mood state has worsened. For example, processor 34 may order stored
mood states based on severity of mood states, and determine that
the patient mood state has worsened based on the change between the
mood states. In this way, determining which of a plurality of
stored mood states the physiological parameter of patient 14
indicates may be useful for distinguishing between patient mood
states. Different therapy parameter values may be more efficacious
for different patient mood states. Thus, an ability to determine
different mood states of patient 14 based on a physiological
parameter may help provide patient 14 with efficacious psychiatric
disorder therapy.
[0245] In some embodiments, processor 34 may also receive input
from patient 14 indicating a mood state. For example, when patient
14 feels a negative mood state, patient 14 may interact with user
interface 44 of patient programmer 24 (FIG. 3), such as by pressing
a button dedicated to indicating a negative mood state or by a
multi-function button or other user input mechanism. In some
embodiments, processor 34 may determine the patient mood state
based on both the physiological signal and the patient input.
Processor 34 may apply equal weights or different weights to the
physiological signal and the patient input. Processor 34 may
dynamically change the weight applied to the patient input and
physiological signal over time.
[0246] If processor 34 does not detect a negative mood state (214),
processor 34 may control therapy module 32 to stop therapy delivery
(216). Processor 34 may then continue monitoring the physiological
parameter and determining the associated mood state (212) until a
negative mood state is detected (214), at which time processor 34
may initiate the delivery of therapy to patient 14 (210). In the
technique shown in FIG. 17, IMD 16 substantially continuously
delivers stimulation therapy to patient 14 until a negative mood
state is not detected. Alternatively, IMD 16 may substantially
continuously deliver stimulation therapy to patient 14 until a
positive mood state is detected.
[0247] FIG. 18 is a flow diagram illustrating another embodiment of
a technique for controlling the delivery of therapy to patient 14
based on a patient mood state. Processor 34 may control therapy
module 32 to deliver therapy to patient 14 according to one or more
therapy programs determined to provide efficacious therapy to
patient 14 (210). Processor 34 may control therapy module 32 to
deliver the therapy for a limited period of time, rather than
substantially continuously. For example, processor 34 may control
therapy module 32 to deliver therapy for about a few seconds to one
minute or more (i.e., an "on-cycle") Thereafter, processor 34 may
control therapy module 32 to stop therapy delivery (217). After
therapy delivery has been stopped, i.e., during an off-cycle of the
therapy, processor 34 may monitor a physiological parameter of
patient to determine which patient mood state from among a
plurality of stored mood states the physiological parameter
indicates (212). Again, processor 34 may use any of the techniques
described above with respect to FIGS. 12, 14, and 15 to associate a
mood state with a monitored physiological signal and determine a
mood state. In some embodiments, processor 34 may also receive
input from patient 14 indicating a mood state, as described above
with respect to FIG. 17.
[0248] If processor 34 detects a negative mood state (214) during
the post-stimulation period, processor 34 may initiate therapy
delivery to patient 14 (210). The frequency at which processor 34
determines the patient's mood state may be selected such that
processor 34 detects a negative mood state relatively quickly
(e.g., within less than a minute), thereby enabling processor 34 to
deliver responsive therapy to the change in the patient's mood
state. In some embodiments, processor 34 may also modify the
therapy program if processor 34 determines that the current therapy
program is not efficacious. If processor 34 does not detect a
negative mood state (214) during the post-stimulation period,
therapy module 32 may remain in the off-cycle and processor 34 may
continue monitoring the physiological signal (212) until a negative
mood state is detected, i.e., until a physiological signal of
patient 14 indicates that therapy delivery is desirable.
[0249] If sensing module 26 or other physiological parameter
monitoring systems fail, processor 34 may automatically switch to a
particular on-cycle and off-cycle based on a history of the
patient's response to therapy. For example, processor 34 may
determine that based on the past on-cycle and off-cycle durations,
therapy module 32 remained off after a therapy on-cycle for about
20 hours (which is used merely as an example), at which time a
negative mood state was detected and therapy module 32 was shifted
back to the on-cycle. Accordingly, in the event that sensor 26
fails, processor 34 may control therapy module 32 to deliver
therapy to patient 14 with on-cycles separated by an approximately
20 hour off-cycle. In other embodiments, if sensing module 26 or
other physiological parameter monitoring systems fail, the
processor 34 may also be default such that therapy module 32
delivers therapy in a continuous stimulation or open loop mode.
[0250] In addition, in some embodiments, if processor 34 determines
that patient 14 provides a substantially consistent response to
therapy delivery over a period of time, such as three months to 12
months, such that therapy module 32 delivers therapy to patient 14
with a substantially consistent off-cycle between therapy delivery,
processor 34 may control sensor 26 to shut down or enter a sleep
mode (a low power mode) to conserve energy. In this way, therapy
system 10 may convert to an open-loop therapy system.
[0251] The therapy delivery techniques described with respect to
FIGS. 17 and 18 may provide a dynamic on/off cycle for therapy
delivery to patient 14. In addition, the therapy delivery
techniques described with respect to FIGS. 17 and 18 may help
reduce the possibility or speed at which patient 14 adapts to the
therapy. It has also been found that patient 14 may adapt to DBS
provided by IMD 16 over time. That is, a certain level of
electrical stimulation provided to brain 12 may be less effective
over time. This phenomenon may be referred to as "adaptation." As a
result, any beneficial effects to patient 14 from the DBS may
decrease over time. While the electrical stimulation levels (e.g.,
amplitude of the electrical stimulation signal) may be increased to
overcome such adaptation, the increase in stimulation levels may
consume more power, and may eventually reach undesirable or harmful
levels of stimulation.
[0252] FIG. 19 is a conceptual diagram illustrating a stimulation
signal 217 delivered by IMD 16 to a target tissue site within
patient 14 and a corresponding physiological signal 218. Processor
34 may receive physiological signal 218 from sensor 26 or from a
sensing module within IMD 16. Physiological signal 218 may be
received from a separate sensor 26 via a wired or wireless
connection. Processor 34 may determine a patient mood state based
on physiological signal 218. In the embodiment shown in FIG. 19,
processor 34 detects a negative patient mood state when the
amplitude of physiological signal 218 crosses amplitude threshold
A.
[0253] In accordance with the technique shown in either FIG. 17 or
18, processor 34 may continue delivering therapy or resume therapy
when the amplitude of physiological signal 218 crosses (e.g., is
greater than or equal to) threshold A. As shown in FIG. 19,
stimulation signal 217 indicates therapy is delivered to patient
14, as reflected by a higher waveform amplitude, when physiological
signal 218 crosses threshold A. Processor 34 controls IMD 16 to
deliver therapy to patient 14 as long as physiological signal 218
indicates patient 14 is in a negative mood state or otherwise not
in a positive mood state. Thus, in a first instance, the portion of
stimulation signal 217A that indicates IMD 16 was delivering active
stimulation to patient 14 temporally correlates with the portion of
physiological signal 218A, which has an amplitude at or above
threshold T.
[0254] Processor 34 controls therapy module 32 to being delivering
therapy to patient 14 at time T1. Upon determining an amplitude of
physiological signal 218 is below threshold A, at time T2,
processor 34 may control therapy module 32 to stop therapy delivery
or at least decrease the intensity of the therapy. Processor 34 may
continue monitoring physiological signal 218 to determine when
signal 218 suggest patient 14 is experiencing a negative mood
state.
[0255] At time T3, processor 34 may determine that the amplitude of
physiological signal is greater than or equal to threshold A, and
initiate therapy delivery, as indicated by portion 217B of
stimulation signal 217. Therapy is delivered until processor 34
determines an amplitude of physiological signal 218 no longer
indicates patient 14 is in the negative mood state, e.g., in the
example shown in FIG. 19, the amplitude of physiological signal 218
falls below threshold A. Thus, stimulation signal portion 217B
corresponds temporally to physiological signal portion 218B.
Similarly, stimulation signal portions 217C, 217D temporally
correlate to physiological signal portions 218C, 218D,
respectively.
[0256] FIG. 19 is merely a conceptual diagram of an example of a
stimulation signal 217 and physiological signal 218. In other
embodiments, other characteristics of physiological signal 218 may
control therapy delivery, and in other embodiments, stimulation
signal 217 may not include pulses, but rather continuous wave
signals. Similarly, other relationships between a stimulation
signal and physiological signal are contemplated and may be
specific to the type of physiological signal monitored and the type
of washout period or stimulation period characteristic used to
associate a patient mood state with a physiological signal
characteristic.
[0257] As previously described, a washout period characteristic or
stimulation period characteristic may be compared to patient input
regarding the efficacy of a tested therapy program, such as to
determine whether the patient input and is consistent with the
washout period characteristic. In some cases, a washout period
characteristic or stimulation period characteristic may be used to
validate patient input regarding the efficacy of a tested therapy
program, such as to determine whether the patient input is
consistent with relatively objective indicia, such as a washout
period characteristic. FIG. 20 is a flow diagram illustrating an
example embodiment of a technique for comparing patient feedback to
therapy delivery according to a therapy program to information
determined based on a washout period characteristic. The technique
shown in FIG. 20 may also be used to compare patient feedback to
therapy delivery according to a therapy program to information
determined based on a stimulation period characteristic.
[0258] The patient feedback may be received, e.g., during a trial
therapy session in which the therapy program is tested for relative
efficacy in managing the patient's psychiatric disorder and
minimizing side effects from the therapy delivery. In other
embodiments, determining whether patient input regarding the
efficacy of a therapy program matches information determined based
on a washout period characteristic may be applicable to therapy
programs for other therapeutic applications, including other DBS
therapies, SCS therapies, peripheral nerve stimulation, and the
like. While the description of FIG. 20 primarily refers to
processor 70 of clinician programmer 22, in other embodiments,
processor 34 of IMD 16, processor 40 of patient programmer 24 or a
processor of another device may implement the technique shown in
FIG. 20, alone or in combination with processor 70.
[0259] Processor 70 may control IMD 16 to deliver therapy to
patient 14 according to a therapy program (120), and processor 70
may determine a characteristic of a washout period resulting from
the therapy delivery, e.g., using the technique described above
with respect to FIG. 8 (180). Processor 70 may determine a patient
mood state based on the washout period characteristic (200), which
may be a probability of the mood state based on previous data
acquired from patient 14 or a plurality of patients. Processor 70
may receive input from patient 14 indicating the efficacy of the
therapy delivered according to the therapy program (220). For
example, processor 70 may prompt the clinician or patient 14 to
input information via user interface 74 (FIG. 4). The information
may be, for example, an overall rating of efficacy, a rating of the
therapeutic benefits, a rating of the side effects, and the like.
The rating information may, but need not be, based on a numerical
rating scale or may be determine based on the patient's answer to
one or more questions. In some embodiments, the rating information
may merely be textual notes inputted by the clinician or patient
14.
[0260] Processor 70 may compare the patient input regarding
efficacy to the mood state determined based on the washout period
characteristic (222) and determine whether the patient input and
mood state determination match (224), e.g., whether the patient
input and determined mood state are consistent. For example,
processor 70 may determine whether the washout period
characteristic is associated with a positive patient mood state,
which as previously described may be an objectively positive mood
state, such as a non-depressive mood state, or may merely be an
improvement from the patient's baseline mood state, and whether the
patient's input also indicates a positive mood state. If the mood
state determined based on the washout period characteristic is a
positive mood state, and patient 14 indicates that the therapy
delivery according to the therapy program did not provide any
beneficial results, processor 70 may determine that the patient
input and determined mood state are inconsistent (224).
[0261] Similarly, if the mood state determined based on the washout
period characteristic is a negative mood state, which may be an
objectively negative mood state, such as severe depressive mood
state, or may be a degradation in the patient's baseline state,
such as a change from a moderate depressive mood state to a severe
depressive mood state, and patient 14 provides input indicating
that the therapy delivery according to the therapy program provided
beneficial results, processor 70 may determine that the patient
input and the mood state determined based on the washout period
characteristic are inconsistent (224).
[0262] Processor 70 may record an inconsistency indication in
memory 72 (FIG. 4) that indicates that the patient input in
response to the test therapy delivery according to the therapy
program was inconsistent with the mood state determined based on
the washout period characteristic (226). The inconsistency
indication may be, for example, a value, flag or signal that is
stored in memory 72 (FIG. 4) of clinician programmer 22 and
associated with the therapy program. The clinician may review the
recorded information, and, if desired, retest the therapy program
may by delivering therapy according to the therapy program. In some
cases, processor 70 may automatically retest the therapy program by
controlling IMD 16 to deliver therapy according to the therapy
program in a subsequent trial, which may, but need not, immediately
follow the prior trial therapy delivery according to the therapy
program. In other embodiments, processor 70 may generate a prompt
and receive clinician approval prior to retesting the therapy
program.
[0263] In some cases, if the patient input and mood state
determination are inconsistent, the clinician may determine whether
the washout period characteristic or the patient input is entitled
to more weight with respect to evaluating the therapy program. For
example, the clinician may determine that patient 14 has provided
inconsistent, inaccurate or untruthful responses in the past, and,
therefore, attribute more weight to the mood state determination
based on the washout period characteristic. The clinician may
provide input to programmer 22 indicating whether the patient input
or washout period characteristic is entitled to more weight. If the
clinician selects the washout period characteristic as the more
reliable indicia of patient mood and the patient input and mood
state determination are inconsistent, processor 70 may determine
that the patient input was invalid (or entitled to less weight) due
to its inconsistency with the mood state determined based on the
washout period characteristic. On the other hand, if the clinician
selects the patient input as the more reliable indicia of patient
mood and the patient input and mood state determination are
inconsistent, processor 70 may determine that the mood state
determination based on a washout period characteristic was invalid
(or entitled to less weight) due to its inconsistency with the mood
state determined based on the patient input.
[0264] Processor 70 may generate a notification to the clinician
that the patient input was inconsistent with the determined mood
state. In some embodiments, processor 70 may prompt patient 14 to
input more detailed information evaluating the efficacy of the
therapy program. Processor 70 may determine, for example, whether
patient 14 provided input that was inconsistent with the determined
patient mood state because the therapy delivery according to the
therapy program resulted in a positive mood state, but also
generated side effects that patient 14 deemed to render the therapy
program unacceptable, e.g., subjectively non-efficacious.
[0265] If the mood state determined based on the washout period
characteristic and the patient input are consistent, e.g., match
(224), processor 70 may record a consistency indication in memory
72 and associate the input with the therapy program (228). The
therapy program may be implemented for chronic therapy delivery or
may be retested at a later time. Processor 70 may determine that
the patient input is consistent with the mood state determined
based on the washout period characteristic if the mood state
determined based on the washout period characteristic is a positive
mood state, and patient 14 indicates that the therapy delivery
according to the therapy program provided beneficial results.
Similarly, processor 70 may determine that the patient input is
consistent with the mood state determined based on the washout
period characteristic if the mood state determined based on the
washout period characteristic is a negative mood state, and patient
14 indicates that the therapy delivery according to the therapy
program did not provide beneficial results.
[0266] After testing a plurality of therapy programs and
associating each tested therapy program with consistency or
inconsistency indications, the clinician may evaluate the therapy
programs based on the consistency or inconsistency indications. For
example, processor 70 may order the list of therapy programs
according to the consistency or inconsistency indications in order
to allow the clinician to relatively quickly discern which therapy
programs resulted in consistent mood state determinations based on
a washout period characteristic and patient input. In some
examples, processor 70 may order the list of therapy programs
according to the consistency or inconsistency indications. For
example, processor 70 may order the list of therapy programs
according to the total number of consistency or inconsistency
indications associated with the therapy programs, or according to a
percentage that represents the percentage of trials that the
patient's input matched the mood state determined based on the
physiological signal (e.g., the washout period characteristic or a
stimulation period characteristic).
[0267] If, for example, 3 out of 5 trials of a therapy program
(e.g., testing for a limited period of time) resulted in a match
between the patient input and mood state, such that 3 consistency
indications and 2 inconsistency indications are associated with the
therapy program, the match percentage associated with the therapy
program may be about 60% and the non-match percentage may be about
40%. The list of tested therapy programs may be ordered upon
receiving instructions from clinician indicating the list of
therapy programs should be ordered according to the consistency or
inconsistency indications. In some cases, the consistency and
inconsistency indications may be a part of an overall metric for
evaluating therapy programs, such as the overall metric described
above with respect to FIG. 9.
[0268] Evaluating a list of therapy programs based on whether the
therapy programs resulted in consistent patient input indicating a
mood state and mood state determination based on a washout period
characteristic may be useful for increasing the clinician's
confidence about the efficacy of a therapy program. For example, if
a therapy program is tested one or more times and has a relatively
low match rate (e.g., in terms of percentage of matches for two or
more trials), as indicated by the number of consistency or
inconsistency indications associated with the therapy program, the
clinician may determine that the therapy program is not as
efficacious as another therapy program that has a relatively high
match rate. In addition, the consistency or inconsistency
indications associated with the therapy programs may be useful for
differentiating between two therapy programs that are associated
with relatively similar patient efficacy inputs.
[0269] The technique shown in FIG. 20 may be performed after a
washout period characteristic of a physiological signal has been
associated with a patient mood state, as described with respect to
FIG. 11. In other embodiments, the technique shown in FIG. 20 may
be performed without associating washout period characteristics
with a patient mood state. For example, activity of a physiological
signal during a post-stimulation period may indicate the therapy
delivery according to the therapy program resulted in a detectable
physiological effect on patient 14. Accordingly, if patient 14
provides input stating that the therapy delivery according to the
therapy program did not have any effect, therapeutic or not, on
patient 14, the clinician may evaluate the therapy program based on
whether the patient's input matches information gained from the
physiological signal during the post-stimulation period, which may
be automatically detected.
[0270] As an example, if the clinician notices a relatively large
change in a signal indicating the heart rate of patient 14, but the
patient provides input indicating that no physiological effect was
felt, the clinician may determine that the therapy program provided
inconsistent physiological signal morphology and patient input. The
clinician may then apply less weight to the therapy program
associated with the inconsistent patient input and physiological
effects when selecting therapy programs to implement for chronic
therapy delivery for patient 14. In some cases, the inconsistency
between the activity of physiological signal during the
post-stimulation period, indicating a carryover effect, and the
patient's input may prompt the clinician to retest the therapy
program.
[0271] While the description primarily refers to electrical
stimulation therapy, in some cases, a characteristic of a washout
period following the delivery of a therapeutic agent to patient 14
may be determined. Just as with the therapy systems 10 described
above, for a therapy system that includes delivery of a therapeutic
agent, one or more physiological parameters of patient 14 may be
monitored in order to detect the washout period and determine a
washout period characteristic, such as a brain activity, heart
rate, respiratory rate, electrodermal activity, facial
electromyogram or thermal activity of the patient's body.
[0272] In the case of therapeutic agent delivery, the therapy
parameters may include the dosage of the therapeutic agent (e.g., a
bolus size or concentration), the rate of delivery of the
therapeutic agent, the maximum acceptable dose in each bolus, a
time interval at which a dose of the therapeutic agent may be
delivered to a patient (lock-out interval), and so forth. Example
therapeutic agents include, but are not limited to, selective
serotonin reuptake inhibitor drugs, amitriptyline, amoxapine,
benzodiazepines, bupropion, clomipramine, desipramine, doxepin,
imipramine, monoamine oxidase inhibitors, maprotiline, mirtazapine,
nefazodone, nortriptyline, protriptyline, trazodone, trimipramine,
venlafaxines to manage OCD, anxiety disorders or MDD; alprazolam,
buspirone, chlordiazepoxide, clonazepam, diazepam, halazepam,
lorazepam, oxazepam, prazepam to manage anxiety disorders; and
carbamazepine, depakote, divalproex sodium (valproic acid),
gabapentin, lamotrigine, lithium carbonate, lithium citrate or
topimarate to manage bipolar disorder.
[0273] The disclosure also contemplates computer-readable media
comprising instructions to cause a processor to perform any of the
functions described herein. The computer-readable media may take
the form of any volatile, non-volatile, magnetic, optical, or
electrical media, such as a RAM, ROM, NVRAM, EEPROM, flash memory,
or any other digital media. A programmer, such as clinician
programmer 22 or patient programmer 24, may also contain a more
portable removable memory type to enable easy data transfer or
offline data analysis.
[0274] The techniques described in this disclosure, including those
attributed to IMD 16, programmers 22, 24, or various constituent
components, may be implemented, at least in part, in hardware,
software, firmware or any combination thereof For example, various
aspects of the techniques may be implemented within one or more
processors, including one or more microprocessors, DSPs, ASICs,
FPGAs, or any other equivalent integrated or discrete logic
circuitry, as well as any combinations of such components, embodied
in programmers, such as physician or patient programmers,
stimulators, image processing devices or other devices. The term
"processor" or "processing circuitry" may generally refer to any of
the foregoing logic circuitry, alone or in combination with other
logic circuitry, or any other equivalent circuitry.
[0275] Such hardware, software, firmware may be implemented within
the same device or within separate devices to support the various
operations and functions described in this disclosure. While the
techniques described herein are primarily described as being
performed by processor 40 of IMD 16 and/or processor 60 of
programmer 14, any one or more parts of the techniques described
herein may be implemented by a processor of one of IMD 16,
programmer 14, or another computing device, alone or in combination
with each other.
[0276] In addition, any of the described units, modules or
components may be implemented together or separately as discrete
but interoperable logic devices. Depiction of different features as
modules or units is intended to highlight different functional
aspects and does not necessarily imply that such modules or units
must be realized by separate hardware or software components.
Rather, functionality associated with one or more modules or units
may be performed by separate hardware or software components, or
integrated within common or separate hardware or software
components.
[0277] When implemented in software, the functionality ascribed to
the systems, devices and techniques described in this disclosure
may be embodied as instructions on a computer-readable medium such
as RAM, ROM, NVRAM, EEPROM, FLASH memory, magnetic data storage
media, optical data storage media, or the like. The instructions
may be executed to support one or more aspects of the functionality
described in this disclosure.
[0278] Many embodiments of the disclosure have been described.
Various modifications may be made without departing from the scope
of the claims. These and other embodiments are within the scope of
the following claims.
* * * * *