U.S. patent application number 13/961963 was filed with the patent office on 2016-06-16 for medical device to provide breathing therapy.
The applicant listed for this patent is MEDTRONIC, INC.. Invention is credited to Yong K. Cho, Shaileshkumar V. Musley, Avram Scheiner.
Application Number | 20160166831 13/961963 |
Document ID | / |
Family ID | 52449263 |
Filed Date | 2016-06-16 |
United States Patent
Application |
20160166831 |
Kind Code |
A9 |
Cho; Yong K. ; et
al. |
June 16, 2016 |
MEDICAL DEVICE TO PROVIDE BREATHING THERAPY
Abstract
Medical devices and methods for providing breathing therapy
(e.g., for treating heart failure, hypertension, etc.) may
determine at least the inspiration phase of one or more breathing
cycles based on the monitored physiological parameters and control
delivery of a plurality of breathing therapy sessions (e.g., each
of the breathing therapy sessions may be provided during a defined
time period). Further, each of the plurality of breathing therapy
sessions may include delivering stimulation after the start of the
inspiration phase of each of a plurality of breathing cycles to
prolong diaphragm contraction during the breathing cycle.
Inventors: |
Cho; Yong K.; (Excelsior,
MN) ; Musley; Shaileshkumar V.; (Blaine, MN) ;
Scheiner; Avram; (Vadnais Heights, MN) |
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Applicant: |
Name |
City |
State |
Country |
Type |
MEDTRONIC, INC. |
MINNEAPOLIS |
MN |
US |
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Prior
Publication: |
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Document Identifier |
Publication Date |
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US 20150045848 A1 |
February 12, 2015 |
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Family ID: |
52449263 |
Appl. No.: |
13/961963 |
Filed: |
August 8, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13192914 |
Jul 28, 2011 |
8509902 |
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13961963 |
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Current U.S.
Class: |
607/18 |
Current CPC
Class: |
A61B 5/0205 20130101;
A61B 5/0816 20130101; A61N 1/36585 20130101; A61B 5/6877 20130101;
A61N 1/36521 20130101; A61B 5/6869 20130101; A61B 5/0809 20130101;
A61N 1/3601 20130101; A61B 5/02405 20130101 |
International
Class: |
A61N 1/36 20060101
A61N001/36; A61N 1/365 20060101 A61N001/365 |
Claims
1. A method for providing breathing therapy, comprising: providing
a plurality of breathing therapy sessions wherein each of the
plurality of breathing therapy sessions comprises delivering
stimulation during each of a plurality of breathing cycles to
prolong diaphragm contraction during the breathing cycle and
delivering cardiac pacing to the patient based on a predefined
ratio of breathing rate to heart rate.
2. The method of claim 1 further comprising: monitoring one or more
physiological parameters of a patient to determine a presence of a
temporary or sustained elevated sympathetic tone based on at least
an elevated blood pressure; and monitoring respiration of a patient
to determine at least an inspiration phase of one or more breathing
cycles.
3. The method of claim 2, wherein the plurality of breathing
therapy sessions upon determination of the presence of an elevated
sympathetic tone, wherein each of the breathing therapy sessions is
provided during a defined time period, and further wherein each of
the plurality of breathing therapy sessions comprises delivering
stimulation after the start of the inspiration phase of each of a
plurality of breathing cycles to prolong diaphragm contraction
during the breathing cycle.
4. The method of claim 3, wherein delivering stimulation comprises
delivering at least one of phrenic nerve stimulation, diaphragmatic
stimulation, intercostal muscle stimulation, and central
respiratory control center stimulation to control the breathing
cycle of the patient.
5. The method of claim 3, wherein delivering stimulation comprises
delivering phrenic nerve stimulation after the start of the
inspiration phase of each of a plurality of breathing cycles and
prior to termination of the inspiration phase of such breathing
cycles to prolong diaphragm contraction during the breathing
cycle.
6. The method of claim 3, wherein providing the plurality of one or
more breathing therapy sessions comprises providing one or more
breathing therapy sessions during each of a plurality of days.
7. The method of claim 3, wherein each of the plurality of
breathing therapy sessions comprises: determining a current
breathing cycle length for the patient and duration of the
inspiration phase of the current breathing cycle; setting a target
breathing cycle length for the patient; delivering stimulation
after the start of the inspiration phase of each of a plurality of
breathing cycles and prior to termination of the inspiration phase
of such breathing cycles to provide an increasing diaphragm
contraction prolongation over the plurality of breathing cycles
until the target breathing cycle length of the patient is
attained.
8. The method of claim 7, wherein the duration and/or amplitude of
the stimulation delivered over the plurality of breathing cycles
follows an increasing linear function.
9. The method of claim 7, wherein each of the plurality of
breathing therapy sessions further comprises continuing stimulation
after the target breathing cycle length of the patient is attained
to maintain the target breathing cycle length of the patient until
the end of the predefined time period for the breathing therapy
session.
10. The method of claim 7, wherein each of the plurality of
breathing therapy sessions further comprises delivering cardiac
pacing to the patient based on a predefined ratio of inspiration
pacing rate to expiration pacing rate.
11. The method of claim 7, wherein the method further comprises
providing the plurality of breathing therapy sessions when the
patient is not cognitive of respiratory control.
12. The method of claim 11, wherein the method further comprises
determining when the patient is sleeping, and further wherein the
plurality of breathing therapy sessions are provided when the
patient is sleeping.
13. The method of claim 3, wherein monitoring one or more
physiological parameters of a patient to determine the presence of
an elevated sympathetic tone comprises determining the presence of
at least one of an elevated blood pressure, an elevated heart rate,
a decreased heart rate variability, decreased muscle sympathetic
nerve activity, a decreased galvanic skin response, and an
increased respiratory rate.
14. The method of claim 3, wherein the method further comprises
monitoring the one or more physiological parameters of a patient to
determine a change in the elevated sympathetic tone and adjusting
one or more characteristics of one or more breathing therapy
sessions based thereon.
15. The method of claim 14, wherein the method comprises monitoring
at least blood pressure of the patient to determine a change in the
elevated sympathetic tone and adjusting one or more characteristics
of one or more breathing therapy sessions based thereon.
16. The method of claim 3, wherein the method further comprises
defining a schedule to provide the plurality of breathing therapy
sessions, wherein each of the breathing therapy sessions is
provided during the defined time period such that a patient attains
a target breathing cycle length during the breathing therapy
session.
17. The method of claim 3, wherein providing a plurality of
breathing therapy sessions further comprises delivering one or more
additional therapies during each of the plurality of breathing
therapy sessions, wherein the one or more additional therapies
comprise at least one of carotid sinus stimulation, aortic
baroreceptor stimulation, baroreflex activation therapy, vagus
nerve stimulation, cardiac synchronization therapy, cardiac pacing,
spinal cord stimulation, renal nerve block, and drug therapy.
18. A system for providing breathing therapy, comprising:
processing means for providing a plurality of breathing therapy
sessions wherein each of the plurality of breathing therapy
sessions comprises delivering stimulation during each of a
plurality of breathing cycles to prolong diaphragm contraction
during the breathing cycle and delivering cardiac pacing to the
patient based on a predefined ratio of breathing rate to heart
rate.
19. The system of claim 18 further comprising: monitoring means for
monitoring one or more physiological parameters of a patient to
determine a presence of a temporary or sustained elevated
sympathetic tone based on at least an elevated blood pressure; and
monitoring means for monitoring respiration of a patient to
determine at least an inspiration phase of one or more breathing
cycles.
20. The system of claim 19, wherein the plurality of breathing
therapy sessions upon determination of the presence of an elevated
sympathetic tone, wherein each of the breathing therapy sessions is
provided during a defined time period, and further wherein each of
the plurality of breathing therapy sessions comprises delivering
stimulation after the start of the inspiration phase of each of a
plurality of breathing cycles to prolong diaphragm contraction
during the breathing cycle.
21. The system of claim 20, wherein delivering stimulation
comprises delivering at least one of phrenic nerve stimulation,
diaphragmatic stimulation, intercostal muscle stimulation, and
central respiratory control center stimulation to control the
breathing cycle of the patient.
22. The system of claim 20, wherein delivering stimulation
comprises delivering phrenic nerve stimulation after the start of
the inspiration phase of each of a plurality of breathing cycles
and prior to termination of the inspiration phase of such breathing
cycles to prolong diaphragm contraction during the breathing
cycle.
23. The system of claim 20, wherein the processing means for
providing the plurality of one or more breathing therapy sessions
comprises providing one or more breathing therapy sessions during
each of a plurality of days.
24. An article of manufacture including a machine readable medium
having stored thereon instructions which may be used to program a
system to perform a method, comprising: providing a plurality of
breathing therapy sessions wherein each of the plurality of
breathing therapy sessions comprises delivering stimulation during
each of a plurality of breathing cycles to prolong diaphragm
contraction during the breathing cycle and delivering cardiac
pacing to the patient based on a predefined ratio of breathing rate
to heart rate.
25. The article of manufacture of claim 24 wherein the method
further comprising: monitoring one or more physiological parameters
of a patient to determine a presence of a temporary or sustained
elevated sympathetic tone based on at least an elevated blood
pressure; and monitoring respiration of a patient to determine at
least an inspiration phase of one or more breathing cycles.
26. The article of manufacture of claim 25 wherein the plurality of
breathing therapy sessions upon determination of the presence of an
elevated sympathetic tone, wherein each of the breathing therapy
sessions is provided during a defined time period, and further
wherein each of the plurality of breathing therapy sessions
comprises delivering stimulation after the start of the inspiration
phase of each of a plurality of breathing cycles to prolong
diaphragm contraction during the breathing cycle.
Description
RELATED APPLICATION
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/192,914, filed Jul. 28, 2011 entitled
"MEDICAL DEVICE TO PROVIDE BREATHING THERAPY", herein incorporated
by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] The disclosure herein relates to devices and/or methods for
treating conditions, such as heart failure, hypertension, etc.,
using breathing therapy.
[0003] Heart failure typically refers to the inability of the heart
to keep up with the functional demands made upon it. Congestive
heart failure typically refers to an inability of the heart to pump
an adequate amount of blood to the body tissues. In other words,
congestive heart failure is characterized by inadequate cardiac
output.
[0004] Because the heart is unable to pump an adequate amount of
blood, blood returning to the heart becomes congested in the venous
and pulmonary system. A patient with congestive heart failure may
be unable to pump enough blood forward to provide an adequate flow
of blood to the kidneys, for example, causing the patient to retain
excess water and salt. The patient's heart may also be unable to
handle the blood returning from the patient's pulmonary system,
resulting in a damming of the blood in the lungs and increasing the
risk of developing pulmonary edema.
[0005] Symptoms experienced by a patient with congestive heart
failure may include breathing difficulty caused by pulmonary edema,
swelling, particularly of the lower extremities, fatigue,
difficulty concentrating, dizziness, and fainting. During periods
where a patient with congestive heart failure is experiencing
severe symptoms, breathing difficulty may be such that the patient
cannot lie down to sleep, and the patient may feel as though they
are suffocating.
[0006] Patients with congestive heart failure may be treated with
pharmacological therapies to increase cardiac output. Some patients
with congestive heart failure benefit from an implanted pacemaker
that increases cardiac output by increasing the heart rate, or
synchronizing the contraction of the ventricles of such patients.
When a patient experiences severe symptoms, the patient may be
admitted to a hospital or clinic, and receive supplemental
pharmacological therapy to alleviate the symptoms. This situation
may be very costly because of the hospital stay, nursing costs,
patient transportation costs, and so forth.
[0007] Generally, chronic heart failure (HF) is accompanied by a
sustained elevation in sympathetic nervous system activity (e.g., a
sustained elevation of sympathetic tone) which is thought to be an
important component in the pathophysiology and progression of the
disease. Hypertension or elevated blood pressure is generally
indicative of an elevated sympathetic tone. Further, HF patients
may also show abnormal breathing patterns with an increased
respiratory rate and a lower tidal volume. Faster respiratory rate
is associated with higher levels of sympathetic activity and has a
negative impact on the functioning of the heart. All these factors
contribute to the distressing symptoms of fatigue, dyspnea and
exercise intolerance in these patients.
[0008] It has been shown that when a slow breathing technique was
taught to patients with heart failure (e.g., employing a scripted
technique that directed patients to modify their breathing rate),
they had a reduction in their sensation of shortness of breath and
an improvement in their exercise performance (see, Swanson et al.,
"The effect of biofeedback on function in patients with heart
failure" Appl Psychophysiol Biofeedback, 2009; 34(2):71-91).
Further, studies have shown that slow breathing, when directed and
performed routinely, can lower blood pressure (see Elliot et al.,
"Graded blood pressure reduction in hypertensive outpatients
associated with use of a device to assist with slow breathing," J
Clin Hypertens, 2004; 6(10):553-9; and Viskoper et al.,
"Nonpharmacologic Treatment of Resistant Hypertensives By
Device-Guided Slow Breathing Exercises," AJH, 2003; 16:484-487.
[0009] Further, U.S. Pat. App. Pub. No. US2007/0118183 to Gelfand
et al., published May 24, 2007, and entitled "System and Method to
Modulate Phrenic Nerve to Prevent Sleep Apnea," describes a device
for treating breathing disorders such as central sleep apnea using
stimulation provided to the phrenic nerve through a transvenous
lead system. Unlike other breathing modification devices, such as
"Breathing Pacemakers" of Avery Biomedical Devices, Inc. that
stimulate the phrenic nerves to cause diaphragm contraction, U.S.
Pat. App. Pub. No. US2007/0118183 describes use of stimulation
beginning after inspiration to extend the duration of a breath and
to hold the diaphragm in a contracted condition (e.g., prolong
diaphragm contraction).
SUMMARY
[0010] The disclosure herein relates generally to the use of
diaphragm contraction prolongation during breathing therapy
sessions (e.g., when a patient is not cognitive of respiratory
control, such as when they are sleeping) to treat, for example, one
or more characteristics of heart failure or hypertension (e.g.,
which may be determined or identified by an increase in sympathetic
tone, such as by an elevated blood pressure). Such breathing
therapy may, for example, restore or simulate cardiopulmonary
biofeedback to provide biofeedback therapy, e.g., to improve
respiratory sinus arrhythmia (RSA), heart rate variability (HRV),
etc. Use of breathing therapy sessions that apply diaphragm
contraction prolongation, such as when a patient is not cognitive
of respiratory control, may not even be noticeable to a patient.
The prolongation may effectively extend the respiratory cycle of
the patient and, for example, continued or continuous application
of the technique during breathing sessions may slow the breathing
rate. For example, diaphragm contraction prolongation (DCP) can be
activated one or more times (e.g., therapy sessions) during each of
one or more days (i.e., during 24 hour periods) and continued for a
predetermined duration (e.g., 15-30 minutes) during each of such
times (e.g., during each therapy session).
[0011] An exemplary medical device (e.g., an implantable medical
device) for providing breathing therapy may include monitoring
apparatus configured to monitor one or more physiological
parameters of a patient (e.g., may include an electrode as part of
a lead to monitor one or more physiological parameters of a patient
such as termination of an inspiration phase of a breathing cycle);
a therapy delivery module configured to deliver electrical
stimulation to a patient in which the presence of an elevated
sympathetic tone (e.g., temporary or sustained) has been determined
(e.g., the elevated sympathetic tone may be determined based at
least on an elevated blood pressure); and a control module. The
control module may be configured to determine at least the
inspiration phase of one or more breathing cycles based on the
monitored physiological parameters and control delivery of a
plurality of breathing therapy sessions. For example, each of the
breathing therapy sessions may be provided during a defined time
period, and further wherein each of the plurality of breathing
therapy sessions may include delivering stimulation after the start
of the inspiration phase of each of a plurality of breathing cycles
(e.g., such as prior to termination of the inspiration phase of
such breathing cycles) to prolong diaphragm contraction during the
breathing cycle.
[0012] One or more embodiments of the medical device may include
one or more of the following features: the control module may be
configured to determine the presence of a sustained elevation of
sympathetic tone of a patient based on the monitored one or more
physiological parameters of a patient; the therapy delivery module
may be configured to deliver at least one of phrenic nerve
stimulation, diaphragmatic stimulation, intercostal muscle
stimulation, and central respiratory control center stimulation;
the control module may be configured to provide one or more
breathing therapy sessions during each of a plurality of days; the
control module may be configured to determine a current breathing
cycle length for the patient and duration of the inspiration phase
of the current breathing cycle, provide a target breathing cycle
length for the patient, and control delivery of stimulation after
the start of the inspiration phase of each of a plurality of
breathing cycles and prior to termination of the inspiration phase
of such breathing cycles to provide an increasing diaphragm
contraction prolongation over the plurality of breathing cycles
until the target breathing cycle length of the patient is attained
(e.g., delivery of stimulation may be controlled such that the
duration of the stimulation delivered over the plurality of
breathing cycles follows an increasing linear function); the
control module may be configured to control delivery of stimulation
such that, during each of the plurality of breathing therapy
sessions, stimulation is continued after the target breathing cycle
length of the patient is attained to maintain the target breathing
cycle length of the patient until the end of the predefined time
period for the breathing therapy session; the therapy module may be
configured for delivering cardiac stimulation with the control
module being configured to control delivery of cardiac pacing to
the patient based on predefined ratios of breathing rate to heart
rate; the control module may be configured to control delivery of
cardiac pacing to the patient based on a predefined ratio of
inspiration pacing rate to expiration pacing rate; the control
module may be configured to determine when a patient is sleeping
and to provide the plurality of breathing therapy sessions when the
patient is sleeping; the control module may be configured to
determine the presence of an elevated sympathetic tone by at least
one of determining the presence of at least one of an elevated
blood pressure, an elevated heart rate, a decreased heart rate
variability, decreased muscle sympathetic nerve activity, a
decreased galvanic skin response, and an increased respiratory
rate; the control module may be configured to determine a change in
the elevated sympathetic tone and may be configured to adjust one
or more parameters of one or more breathing therapy sessions based
thereon; the control module may be configured to determine a change
in at least blood pressure of the patient to determine a change in
the elevated sympathetic tone and may be configured to adjust one
or more parameters of one or more breathing therapy sessions based
thereon; and the control module may be configured to define a
schedule to provide the plurality of breathing therapy sessions
(e.g., each of the breathing therapy sessions may be provided
during a defined tie period such that a patient attains a target
breathing cycle length during the breathing therapy session).
[0013] One exemplary method described herein for providing
breathing therapy may include monitoring one or more physiological
parameters of a patient to determine the presence of an elevated
sympathetic tone, monitoring respiration of a patient to determine
at least the inspiration phase of one or more breathing cycles, and
providing a plurality of breathing therapy sessions upon
determination of the presence of an elevated sympathetic tone
(e.g., temporary or sustained). Each of the breathing therapy
sessions may be provided during a defined time period, and further,
each of the plurality of breathing therapy sessions may include
delivering stimulation after the start of the inspiration phase of
each of a plurality of breathing cycles (e.g., prior to termination
of the inspiration phase of such breathing cycles) to prolong
diaphragm contraction during the breathing cycle.
[0014] One or more embodiments of the exemplary method may include
one or more of the following steps, processes, or features:
delivering at least one of phrenic nerve stimulation, diaphragmatic
stimulation, intercostal muscle stimulation, and central
respiratory control center stimulation to control the breathing
cycle of the patient (e.g., stimulating after the start of the
inspiration phase of each of a plurality of breathing cycles to
prolong diaphragm contraction during the breathing cycle);
providing one or more breathing therapy sessions during each of a
plurality of days; providing each of the plurality of breathing
therapy sessions by determining a current breathing cycle length
for the patient and duration of the inspiration phase of the
current breathing cycle, setting a target breathing cycle length
for the patient, delivering stimulation after the start of the
inspiration phase of each of a plurality of breathing cycles and
prior to termination of the inspiration phase of such breathing
cycles to provide an increasing diaphragm contraction prolongation
over the plurality of breathing cycles until the target breathing
cycle length of the patient is attained (e.g., the duration and or
amplitude of the stimulation delivered over the plurality of
breathing cycles may follow an increasing linear function);
continuing stimulation after the target breathing cycle length of
the patient is attained to maintain the target breathing cycle
length of the patient until the end of the predefined time period
for the breathing therapy session; delivering cardiac pacing (e.g.,
during the breathing therapy sessions) to the patient based on a
predefined ratio of breathing rate to heart rate; delivering
cardiac pacing (e.g., during the breathing therapy sessions) to the
patient based on a predefined ratio of inspiration pacing rate to
expiration pacing rate; providing the plurality of breathing
therapy sessions when the patient is not cognitive of respiratory
control; determining when the patient is sleeping and providing the
plurality of breathing therapy sessions when the patient is
sleeping; determining the presence of an elevated sympathetic tone
by determining the presence of at least one of an elevated blood
pressure, an elevated heart rate, a decreased heart rate
variability, decreased muscle sympathetic nerve activity, a
decreased galvanic skin response, and an increased respiratory
rate; monitoring the one or more physiological parameters of a
patient to determine a change in the elevated sympathetic tone
(e.g., elevated blood pressure) and adjusting one or more
characteristics of one or more breathing therapy sessions based
thereon; and defining a schedule to provide the plurality of
breathing therapy sessions (e.g., each of the breathing therapy
sessions may be provided during a defined tie period such that a
patient attains a target breathing cycle length during the
breathing therapy session).
[0015] Still further, in one or more embodiments of the medical
device and/or methods, the device may be configured to operate in
combination with one or more additional therapy apparatus
configured to provide delivery of one or more additional therapies
during each of the plurality of breathing therapy sessions. For
example, the one or more additional therapies may include at least
one of carotid sinus stimulation, aortic baroreceptor stimulation,
baroreflex activation therapy, vagus nerve stimulation, cardiac
synchronization therapy, cardiac pacing, spinal cord stimulation,
renal nerve block, and drug therapy.
[0016] The above summary is not intended to describe each
embodiment or every implementation of the present disclosure. A
more complete understanding will become apparent and appreciated by
referring to the following detailed description and claims taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a schematic diagram illustrating exemplary
embodiments of an implantable medical device (IMD) to provide
breathing therapy.
[0018] FIG. 2 is a schematic diagram illustrating one embodiment of
exemplary implanted leads of an implantable medical device (IMD)
operably coupled to a patient's heart.
[0019] FIG. 3 is a block diagram of an exemplary IMD such as shown
in FIG. 1.
[0020] FIG. 4 is a flow chart depicting an exemplary general method
of providing breathing therapy, e.g., using diaphragm contraction
prolongation.
[0021] FIG. 5 is a flow chart depicting an exemplary method of
providing breathing therapy, e.g., using diaphragm contraction
prolongation, such as shown generally in FIG. 4.
[0022] FIG. 6 is a flow chart depicting an exemplary breathing
therapy session, e.g., using diaphragm contraction prolongation,
that may be used in the breathing therapy processes such as shown
in FIGS. 4-5.
[0023] FIG. 7 is a flow chart depicting an exemplary process that
may be used in combination with, for example, the breathing therapy
processes described herein.
[0024] FIG. 8 is a flow chart depicting an exemplary process that
shows use of cardiac pacing therapy in combination with, for
example, the breathing therapy processes (e.g., using diaphragm
contraction prolongation) such as shown in FIGS. 4-6.
[0025] FIG. 9 is a schematic diagram illustrating another
embodiment of an exemplary implantable medical device (IMD)
operably coupled to a patient's heart.
[0026] FIG. 10 is a flow chart depicting an exemplary process that
shows use of other breathing therapies in combination with, for
example, the breathing therapy processes (e.g., using diaphragm
contraction prolongation) such as shown in FIGS. 4-6.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0027] In the following detailed description of illustrative
embodiments, reference is made to the accompanying figures of the
drawing which form a part hereof, and in which are shown, by way of
illustration, specific embodiments which may be practiced. It is to
be understood that other embodiments may be utilized and structural
changes may be made without departing from (e.g., still falling
within) the scope of the disclosure presented hereby.
[0028] Exemplary methods, devices, and systems shall be described
with reference to FIGS. 1-10. It will be apparent to one skilled in
the art that elements or processes from one embodiment may be used
in combination with elements or processes of the other embodiments,
and that the possible embodiments of such methods, devices, and
systems using combinations of features set forth herein is not
limited to the specific embodiments shown in the figures and/or
described herein. Further, it will be recognized that the
embodiments described herein may include many elements that are not
necessarily shown to scale. Still further, it will be recognized
that timing of the processes and the size and shape of various
elements herein may be modified but still fall within the scope of
the present disclosure, although certain timings, one or more
shapes and/or sizes, or types of elements, may be advantageous over
others.
[0029] Elevated (e.g., increased) sympathetic tone may be
associated with the progression of heart failure. For example,
temporary or sustained elevated sympathetic tone (e.g., which may
be indicated by elevated blood pressure or hypertension) may
contribute to the progression of heart failure. Use of breathing
therapy (e.g., automatically controlled breathing therapy, for
example, such as may be delivered when a person is not cognitive of
respiratory control) as described herein may reduce the progression
of heart failure or improve hypertension, e.g., may improve
respiratory sinus arrhythmia (RSA), may increase heart rate
variability (HRV), may increase arterial baroreflex sensitivity,
may decrease blood pressure, may decrease heart rate, may decrease
muscle sympathetic nerve activity (MSNA), may decrease galvanic
skin response (e.g., may decrease skin conductance properties; also
referred to a electrodermal response (EDR)), may decrease
respiratory rate, etc.
[0030] In one embodiment of one or more processes described herein,
one exemplary advantage of using the diaphragm contraction
prolongation technique over other phrenic nerve stimulation
techniques may be that it minimizes certain undesirable effects on
the subject. For example, such a technique may be much more
tolerable to a patient (e.g., may not even be noticeable) as
opposed to, for example, use of continuous stimulation of the
phrenic nerve. Yet, diaphragm contraction prolongation extends the
respiratory cycle and application of this technique over a
plurality of therapy sessions may slow the breathing rate of a
patient.
[0031] Breathing therapy as described herein may be implemented by
one or more various devices (e.g., a medical device that includes
multiple devices or components operable together or separately, an
implantable medical device, etc.) and/or systems. Such devices and
systems may include one or more leads, electronic circuits, power
sources, sensors, electrodes, stimulation devices, monitoring
devices, etc. One example of a medical device that may be used in
carrying out breathing therapy as described herein is depicted in
FIG. 1 as a schematic diagram of an implantable medical device
(IMD).
[0032] The IMD 10, or another monitoring apparatus operable
separately or in combination with the IMD 10, may be configured to
monitor one or more physiological parameters of a patient (e.g.,
electrical activity of a patient, chemical activity of a patient,
hemodynamic activity of a patient, and respiratory activity of a
patient). The monitored physiological parameters, in turn, may be
used to determine whether the patient has an elevated sympathetic
tone (e.g., temporary or sustained), which may be indicated by an
elevated blood pressure (e.g., arterial blood pressure) or
hypertension. For example, in one embodiment, the IMD 10 may
determine that an elevated sympathetic tone state exists (e.g.,
such that breathing therapy may be beneficial). For example, such
an elevated sympathetic tone may be determined based on hemodynamic
measurements of blood pressure.
[0033] As used herein, a temporary elevated sympathetic tone refers
to a sympathetic tone that is determined to be elevated based on
measurements (e.g., a single measurement or multiple measurements
made over a period of time) but which returns to normal at a later
time (e.g., such an elevated condition may reoccur or not reoccur).
As used herein, a sustained elevated sympathetic tone (e.g., a
chronic condition) refers to a sympathetic tone that is elevated
over a long duration or there is a frequent recurrence of such
elevated tone over a long duration of time (e.g., determined based
on measurements made over a relatively long period of time). For
example, further, whether a parameter herein is "elevated" may be
based on a comparison to what is "normal" for an individual or
"normal" for an average person in a similar population.
[0034] As shown in FIG. 1, implantable medical device ("IMD") 10 is
implanted within a patient 12. IMD 10 may be used to provide
breathing therapy as described herein (e.g., using diaphragm
contraction prolongation) by, for example, stimulation of one or
both of right phrenic nerve 14A and left phrenic nerve 14B
(collectively "phrenic nerves 14") via one or more of leads 16A,
16B, and 16C (collectively "leads 16"), as shown in FIG. 1.
Stimulation of phrenic nerves 14 by IMD 10 as described further
herein after the start of the inspiration phase (e.g., prior to
termination of the inspiration phase) causes prolongation of
contraction of diaphragm 18. Repeated stimulation of phrenic nerves
14 by IMD 10 during one or more breathing therapy sessions, may, as
will be described herein, decrease a patient's breathing rate,
e.g., over the long term. For example, IMD 10 may control the
delivery of a plurality of breathing therapy sessions. Each of the
breathing therapy sessions, for example, may be provided during a
defined time period. Further, for example, each of the plurality of
breathing therapy sessions may include delivering stimulation after
the start of the inspiration phase of each of a plurality of
breathing cycles (e.g., prior to termination of the inspiration
phase of such breathing cycles, at the start of expiration, after
the start of expiration, etc.) to prolong diaphragm contraction
during the breathing cycle (e.g., increase the breathing cycle
length).
[0035] IMD 10 may include any number of leads 16. Leads 16 may, as
shown in FIG. 1, extend into heart 20. For example, leads 16 may be
intravascular leads, i.e., enter heart 20 via one or more veins
(not shown) of patient 12. The configuration of leads 16 shown in
FIG. 1 is merely exemplary and any configuration of leads that
provides for suitable stimulation as described herein may be used.
For example, such leads may be positioned with electrodes proximate
the phrenic nerves and not within the heart (e.g., in
configurations that do not also use cardiac pacing).
[0036] Each of leads 16 may include one or more electrodes (not
shown) for delivering stimulation to phrenic nerves 14. Such
electrodes may deliver stimulation to phrenic nerves 14 through the
tissues of heart 20 or the veins. Leads 16 may also include
electrodes by which IMD 10 may sense electrical activity within
heart 20, e.g., sense electrical signals attendant to the
depolarization and re-polarization of heart 20, deliver pacing
pulses to heart 20, deliver defibrillation shocks to heart 20,
and/or monitor pressure or oxygen saturation within heart 20 or
otherwise within the cardiovascular system of patient 12. The
electrodes for delivering stimulation to phrenic nerves 14, sensing
electrical activity, and delivering pulses may be unipolar or
bipolar electrodes, as is well known in the art.
[0037] IMD 10 is not limited to use with intravascular leads 16, or
intravascular or intracardiac electrodes. IMD 10 may deliver
stimulation to phrenic nerves 14, sense electrical activity,
deliver pacing pulses, deliver defibrillation shocks, and monitor
pressure or oxygen saturation from any appropriate site within or
outside of patient 12. For example, IMD 10 may stimulate phrenic
nerves 14 via leads 16 that extend to any point along phrenic
nerves 14, such as a lead that may extend to a point of a phrenic
nerve near the neck of patient 12, a lead that may extend to a
phrenic nerve proximate the heart, a lead that includes coil
electrodes that coil around phrenic nerves 14 (all represented
generally by dashed lines/electrode 17A-17B), as would be known to
one skilled in the art.
[0038] Although the description herein is provided primarily with
respect to the use of phrenic nerve stimulation to provide
breathing therapy, other stimulation may be used to provide such
breathing therapy. For example, as shown generally by dashed
lead(s)/electrode(s) 15, intercostal muscle stimulation may be
used. For example, lead(s) may carry electrode(s) proximate points
associated with the intercostal muscles, which play a role in
respiration, for stimulation thereof to carry out diaphragm
contraction prolongation. Further, for example, as shown generally
by dashed lead(s)/electrode(s) 19, diaphragmatic stimulation may be
used. For example, lead(s) may carry electrode(s) proximate points
associated with the diaphragm for stimulation thereof to carry out
diaphragm contraction prolongation. For example, stimulation may be
delivered to the lower thoracic/upper lumbar region of the spinal
cord to stimulate nerves associated with the intercostal muscles.
Further, for example, electrodes may be inserted directly into the
diaphragm muscle, generally near the motor point (e.g., where the
phrenic nerve enters the diaphragm), electrodes may be placed in
arterial or veins close to the phrenic nerve (e.g., placed in the
pericardiophrenic vein, either unilaterally (such as the left side
only) or bilaterally), electrodes may be placed along side the
phrenic nerve, cuff electrodes may be placed around the phrenic
nerve, etc.
[0039] Still further, for example, as shown generally by dashed
lead(s)/electrode(s) 21, central respiratory control center
stimulation may be used. For example, lead(s) may carry
electrode(s) proximate points in the medullary centers of the brain
which play a role in respiration. Stimulation thereof may be
carried out to provide diaphragm contraction prolongation.
[0040] In one or more embodiments, a single type of stimulation or
multiple types of stimulation may be used to provide diaphragm
contraction prolongation during breathing cycles. For example,
phrenic nerve stimulation may be use alone, or, in at least another
alternate embodiment, an IMD may first stimulate phrenic nerves and
then shortly thereafter stimulate the diaphragm or the intercostal
muscles to provide diaphragm contraction prolongation.
[0041] Still further, for example, as shown in FIG. 1, one or more
additional therapy apparatus 13 may be included to provide
additional therapy in combination with diaphragm contraction
prolongation in combination with (e.g., before, during, or after)
one or more breathing sessions. For example, such additional
therapy apparatus 13 may include apparatus for providing at least
one of carotid sinus stimulation, aortic baroreceptor stimulation,
baroreflex activation therapy, vagus nerve stimulation, spinal cord
stimulation, renal nerve block, and drug therapy.
[0042] For example, baroreflex activation therapy or baroreceptor
stimulation, such as carotid sinus stimulation may be provided
using electrodes placed in or around the carotid artery, e.g., at
the carotid sinus location. Further, for example, aortic
baroreceptor stimulation may be provided using electrodes on, in or
near the aortic arch. For example, one or more embodiments of such
therapies and apparatus for delivering such therapies are described
in the following articles: Navaneethan, et al., Baroreflex
stimulation: A novel treatment option for resistant hypertension,
Journal of the American Society of Hypertension, 3(1) 69-74 (2009);
Durand, et al., Acute and chronic electrical activation of
baroreceptor afferents in awake and anesthetized subjects,
Brazilian Journal of Medical and Biologicial Research, 42: 53-60
(2009); and Sanders, et al., Arterial baroreflex control of
sympathetic nerve activity during elevation of blood pressure in
normal man: dominance of aortic baroreflexes, Pathophysiology and
Natural History-Hypertension, Vol. 77, No. 2, (February 1998).
[0043] For example, spinal cord stimulation may be provided using
electrodes placed in or proximate to the spinal cord at a level to
stimulate cardiac nerves. For example, one or more embodiments of
such therapies and apparatus for delivering such therapies are
described in the articles, Tanaka et al., Mechanisms of sustained
cutaneous vasodilation induced by spinal cord stimulation,
Autonomic Neuroscience: Basic and Clinical, 114, pp. 55-60 (2004);
and Lopshire, et al., Spinal Cord Stimulation Improves Ventricular
Function and Reduces Ventricular Arrhythmias in a Canine
Postinfarction Heart Failure Model, Circulation, 120:286-294 (July
2009).
[0044] For example, renal nerve block may be provided using renal
nerve ablation. For example, the therapy may involve the use of
ablation apparatus to ablate one or more portions of the renal
nerve (e.g., to assist in controlling hypertension). In addition,
drug therapy may be provided using, for example, oral medication,
drug pumps, or any other apparatus for treating a condition (e.g.,
such as hypertension) with one or more drugs.
[0045] Further, for example, vagus nerve stimulation may be carried
out using leads 16 having electrodes positioned proximate the vagus
nerve. For example, use of such therapy in the context of heart
failure is described in Li, et al., Vagal Nerve Stimulation
Markedly Improves Long-Term Survival After Chronic Heart Failure in
Rats, Circulation, 109:120-124 (January 2004).
[0046] Still further, as described herein, the IMD 10 may be used
to provide cardiac synchronization therapy or cardiac pacing in
combination with diaphragm contraction prolongation during
breathing cycles. For example, the pacing may be controlled based
on one or more respiratory characteristics (e.g., controlled to
provide a certain number of heart beats per breath cycle,
controlled to provide a certain number of heart beats in the
inspiration or expiration phase of the breath cycle, controlled to
provide a certain ratio of heart beats in the inspiration phase to
the expiratory phase, etc.). One or more embodiments of using
pacing with diaphragm contraction prolongation during breathing
cycles are described herein with reference to FIGS. 8-9.
[0047] In other words, for example, one or more additional therapy
apparatus 13 may be included to provide one or more of the
additional therapies in combination with diaphragm contraction
prolongation. Various types of apparatus may be used to provide
such additional therapies, and the present disclosure is not
limited to only those listed or provided in the references cited
herein.
[0048] Further, with reference to FIG. 1, and the use of phrenic
nerve stimulation, it will be recognized that either phrenic nerve
14A or phrenic nerve 14B, or both, may be stimulated to provide for
diaphragm contraction prolongation. For example, when IMD 10
stimulates right phrenic nerve 14A, a right half of diaphragm 18
contracts. Similarly, when IMD 10 stimulates left phrenic nerve
14B, a left half of diaphragm 18 contracts. Depending on the
strength of contraction of one of the right and left halves of
diaphragm 18, the other half of diaphragm 18 may be stimulated to
contract via mechanical activation. Diaphragm 18 and phrenic nerves
14 are shown in FIG. 1 in their respective positions after
diaphragm 18 has contracted as segmented lines. As shown in FIG. 1,
when diaphragm 18 contracts, it descends, expanding the volume of
thoracic cavity 22.
[0049] When diaphragm 18 is in the resting position, the pressure
within thoracic cavity 22 is at an equilibrium pressure. When IMD
10 stimulates one or both phrenic nerves 14, causing diaphragm 18
to contract and thoracic cavity 22 to expand, the pressure within
thoracic cavity 22 decreases relative to the pressure of the
atmosphere outside of patient 12, causing air to enter the lungs
(not shown) of patient 12. As air fills the lungs, the pressure
within thoracic cavity 22 begins to return to the equilibrium
pressure. When diaphragm 18 recoils, the pressure within thoracic
cavity 22 increases beyond the equilibrium pressure, forcing air
out of the lungs, until the equilibrium pressure is again
reached.
[0050] FIG. 2 is a schematic view further illustrating exemplary
leads 16 of IMD 10. Leads 16 may, for example, as shown in FIG. 2,
extend from IMD 10 and enter a left subclavian vein 40 of patient
12. As shown in FIG. 2, leads 16 may extend through left subclavian
vein 40 and superior vena cava 42, and enter heart 20.
[0051] As shown in FIG. 2, lead 16A may extend into right atrium
24. Lead 16A may include an elongated insulative lead body carrying
a number of concentric coiled conductors separated from one another
by tubular insulative sheaths. Located adjacent distal end of lead
16A are bipolar electrodes 44 and 46. Electrode 44 may take the
form of a ring electrode, and electrode 46 may take the form of an
extendable helix electrode mounted retractably within an insulative
electrode head 48. Each of the electrodes 44 and 46 may be coupled
to one of the coiled conductors within the lead body. IMD 10 may
stimulate right phrenic nerve 14A via electrodes 44 and 46. IMD 10
may also use electrodes 44 and 46 for atrial pacing and for sensing
atrial depolarizations. In one or more embodiments, IMD 10 may
include a separate lead 16 with separate electrodes, or separate
electrodes on lead 16A for atrial pacing and sensing.
[0052] Electrodes 44 and 46 may, as shown in FIG. 2, be located
proximate to a lateral wall 50 of right atrium 24. IMD 10 may more
easily stimulate right phrenic nerve 14A when electrodes 44 and 46
are proximate to lateral wall 50. The distal end of lead 16A and
electrodes 44 and 46 may, in some embodiments, be located proximate
to a lateral wall 52 of superior vena cava 42.
[0053] In some embodiments, lead 16A may also, as shown in FIG. 2,
include bipolar electrodes 54 and 56 located near the junction of
left subclavian vein 40 and a left innominate vein 59. IMD 10 may
stimulate left phrenic nerve 14B via electrodes 54 and 56. In other
embodiments, IMD 10 may stimulate both phrenic nerves 14 with a
single stimulus via a first unipolar electrode (not shown) located
at the distal end of lead 16A, and a second unipolar electrode (not
shown) located near the junction of left subclavian vein 40 and
left innominate vein 59. In still other embodiments, electrodes 54
and 56 may be located on lead 16B, or on a lead 16 other than leads
16A-C.
[0054] Lead 16A may also, as shown in FIG. 2, include an elongated
coil electrode 58 and a pressure sensor 60. Defibrillation
electrode 58 and pressure sensor 60 may, as shown in FIG. 2, be
located within right atrium 24, or may be located anywhere along
lead 16A. IMD 10 may deliver defibrillation therapy to heart 20 via
defibrillation electrode 58, and may monitor pressure within right
atrium 24 and/or superior vena cava 42 via pressure sensor 60.
Defibrillation electrode 58 and pressure sensor 60 may also be
located on one or more leads other than lead 16A.
[0055] Pressure sensor 60 may sense the absolute pressure of blood
within right atrium 24 and/or superior vena cava 42, and may be
capacitive or piezoresistive pressure sensor. IMD 10 may, for
example, monitor the central venous pressure of heart 20 via
pressure sensor 60.
[0056] As shown in FIG. 2, lead 16B may extend into right ventricle
26. Like lead 16A, lead 16B may include an elongated insulative
lead body carrying a number of concentric coiled conductors
separated from one another by tubular insulative sheaths. Located
adjacent distal end of lead 16B are bipolar electrodes 62 and 64.
Electrode 62 may take the form of a ring electrode, and electrode
64 may take the form of an extendable helix electrode mounted
retractably within an insulative electrode head 66. Each of the
electrodes 62 and 64 is coupled to one of the coiled conductors
within the lead body. IMD 10 may stimulate right phrenic nerve 14A
via electrodes 62 and 64. IMD 10 may also use electrodes 62 and 64
for ventricular pacing and for sensing ventricular depolarizations.
In some embodiments, IMD 10 may include a separate lead 16 with
separate electrodes, or separate electrodes on lead 16B for
ventricular pacing and sensing.
[0057] Electrodes 62 and 64 may, as shown in FIG. 2, be located
proximate to an apex 68 of right ventricle 26. IMD 10 may more
easily stimulate right phrenic nerve 14A when electrodes 44 and 46
are proximate to apex 68. The distal end of lead 16B and electrodes
62 and 64 may, in some embodiments, be located proximate to a
lateral wall 70 of right ventricle 26.
[0058] Like lead 16A, lead 16B may include an elongated coil
electrode 72 and a pressure sensor 74 located within right
ventricle 26. IMD 10 may deliver defibrillation therapy to heart 20
via defibrillation electrode 72, and may monitor pressure within
right ventricle 26 via pressure sensor 74. IMD 10 may, for example,
estimate a pulmonary artery diastolic pressure via pressure sensor
74. Defibrillation electrode 72 and pressure sensor 74 may be
located on one or more leads other than lead 16B.
[0059] Lead 16C may extend into a coronary sinus 76 of heart 20
until a distal end of lead 16 is proximate to left ventricle 28.
Like leads 16A-B, lead 16C may include an elongated insulative lead
body carrying a number of concentric coiled conductors separated
from one another by tubular insulative sheaths. Located adjacent
distal end of lead 16C are bipolar electrodes 78 and 80 indicated
by a broken outline. Electrode 78 may take the form of a ring
electrode, and electrode 80 may take the form of an extendable
helix electrode mounted retractably within an insulative electrode
head 82. Each of the electrodes 78 and 80 is coupled to one of the
coiled conductors within the lead body. IMD 10 may stimulate left
phrenic nerve 14B via electrodes 78 and 80. IMD 10 may also use
electrodes 78 and 80 for ventricular pacing and for sensing
ventricular depolarizations. Lead 16C may include an elongated coil
electrode 84 indicated by a broken outline for delivery of
defibrillation therapy to heart 20.
[0060] In other words, the IMD 10 may monitor pressure or one or
more other physiological parameters of a patient that may indicate
an elevated sympathetic tone. However, in one or more embodiments,
a different monitoring apparatus may be used (not shown) that
monitors one or more physiological parameters of a patient (e.g.,
that may indicate an elevated sympathetic tone, such as with
measurements of arterial blood pressure). For example, the monitor
or the IMD may include a pressure monitor, oxygen saturation
monitor, etc. A pressure monitor may, for example, monitor the
pressure within right ventricle 26 to estimate the pulmonary artery
diastolic pressure based on the rate of change of the right
ventricular pressure over time. Increased pulmonary artery
diastolic pressure may indicate an elevated sympathetic tone (e.g.,
inadequate cardiac output). A pressure monitor or IMD may also
monitor arterial pulse pressure, central venous pressure, right
ventricular end diastolic pressure, left ventricular end diastolic
pressure, pulmonary capillary wedge pressure, or the like. An
oxygen saturation monitor or an IMD may monitor the oxygen
saturation of hemoglobin within the arterial and/or venous blood of
patient 10. Decreased arterial or venous oxygen saturation, or an
increased difference between the arterial and venous oxygen
saturations may indicate an elevated sympathetic tone (e.g.,
inadequate cardiac output). In other words, one or more of such
physiological parameters may be measured to determine an elevated
sympathetic tone.
[0061] Further, IMD 10 may stimulate one or both of phrenic nerves
14 via any one of or combination of the bipolar and unipolar
electrodes and electrode locations described herein. Moreover, IMD
10 need not deliver pacing pulses to any chamber 24-28 of heart 20,
need not deliver defibrillation therapy to heart 20, and need not
monitor pressure within heart 20. The electrodes, sensors, and
electrode and sensor locations are merely provided as examples of
electrodes, sensors, and electrode and sensor locations that may be
used in various embodiments of IMD 10.
[0062] FIG. 3 is a general exemplary functional block diagram of an
IMD 10, such as shown generally in FIG. 1. IMD 10 generally
includes timing and control circuitry 152 and an operating system
that may employ microprocessor 154 or a digital state machine for
timing sensing and therapy delivery functions and controlling other
device functions in accordance with a programmed operating mode.
Microprocessor 154 and associated memory 156 are coupled to the
various components of IMD 110 via a data/address bus 155. IMD 110
includes therapy delivery module 150 for delivering a breathing
therapy, or any other therapy described herein, such as electrical
stimulation or drug therapy, under the control of timing and
control circuitry 152. Therapy delivery module 150 may include
pulse-generating circuitry 151 for generating electrical
stimulation pulses (e.g., electrical stimulation pulses) under the
control of timing and control circuitry 152. As will be described
herein, pulse-generating circuitry 151 may generate stimulation
pulses for stimulating the phrenic nerve, intercostal muscles, the
diaphragm, medullary centers, etc. for use in providing breathing
therapy. Further, for example, as will be described herein,
pulse-generating circuitry 151 may generate stimulation pulses for
providing pacing of the heart.
[0063] For delivering electrical stimulation pulses,
pulse-generating circuitry 151 may be coupled to two or more
electrodes 168 (e.g., such as implemented by the electrodes of
leads 16) via a switch matrix 158. Switch matrix 158 may be used
for selecting which electrode and corresponding polarities are used
for delivering electrical stimulation pulses. Electrodes 168 may
include lead-based electrodes, leadless electrodes incorporated on
IMD 10, and/or the IMD housing configured for use as a can or case
electrode.
[0064] Therapy delivery module 150 may further include high voltage
circuitry for generating high voltage cardioversion/defibrillation
shocks. Aspects of the present disclosure may be embodied in an
implantable cardioverter defibrillator including high voltage
circuitry as generally disclosed in U.S. Pat. No. 6,731,978 to
Olson et al., incorporated herein by reference in its entirety.
[0065] Further, in one or more embodiments, electrodes 168 may also
be used for sensing electrical signals within the body, such as
cardiac signals or impedance signals, such as for use in monitoring
respiration. Electrical signals are sensed using any of electrodes
168 for use in determining the heart rhythm and/or for determining
when therapy may be needed, and in controlling the timing of
stimulation pulses. In other words, the IMD 10 may include
monitoring apparatus, which includes electrodes 168 amongst other
things, for determining an elevated sympathetic tone, for
monitoring parameters to adjust breathing therapy, for verifying
the effectiveness of the breathing therapy, etc.
[0066] Electrodes used for sensing and electrodes used for
stimulation (e.g., such as implemented by the electrodes of leads
16) may be selected via switch matrix 158. When used for sensing,
electrodes 168 may be coupled to signal processing circuitry 160
via switch matrix 158. Processing circuitry 160 may include sense
amplifiers and other signal conditioning circuitry, and one or more
analog to digital converters. In other words, the IMD 10 may
include a sensing module, e.g., includes switch matrix 158, signal
processing circuitry 160, etc. Electrically sensed signals may then
be used by microprocessor 154 for detecting physiological
parameters or events, such as detecting an elevated sympathetic
tone, elevated blood pressure, etc.
[0067] The monitoring apparatus of the IMD 10 may further include
sensors 170 such as pressure sensors, accelerometers, flow sensors,
blood chemistry sensors, activity sensors, and/or other
physiological sensors known for use with IMDs. Sensors 170 are
coupled to IMD 10 via a sensor interface 162 which provides sensor
signals to signal processing circuitry 160. Sensor signals may be
used by microprocessor 154 for detecting physiological events or
conditions (e.g., an elevated sympathetic tone, a sleeping state of
a patient, etc.). For example, IMD 10 may monitor heart wall
motion, blood pressure, blood chemistry, respiration, and/or
patient activity. Monitored signals may be used for sensing the
need for delivering, adjusting, terminating, and/or initiating
breathing therapy under control of the operating system. In other
words, the IMD 10 may include a control module, which may include
the microprocessor 154 and memory 156 and may be configured using
an operating system.
[0068] The operating system includes associated memory 156 for
storing a variety of programmed-in operating modes and parameter
values that are used by microprocessor 154. The memory 156 may also
be used for storing data compiled from sensed signals and/or
relating to device operating history (e.g., for use in delivering,
adjusting, controlling, initiating, and/or terminating therapy)
and/or for communicating such data outside of the patient (e.g.,
using telemetry communication out of recorded history on receipt of
a retrieval or interrogation instruction).
[0069] IMD 10 may further include telemetry circuitry 164 and
antenna 165. Programming commands or data are transmitted during
uplink or downlink telemetry between IMD telemetry circuitry 164
and external telemetry circuitry included in a programmer or home
monitoring unit.
[0070] For example, in one or more embodiments, such as shown in
FIG. 1, IMD 10 may receive a signal from patient 12 indicating a
need for breathing therapy (e.g., patient feels short of breath, an
increased respiratory rate, etc.) via a patient activator or
programmer 32. For example, when patient 12 experiences symptoms
that may be treatable using breathing therapy (e.g., such as
difficulty breathing), patient 12 may place activator 32 over IMD
10, e.g., by placing activator 32 on the chest of patient 12, and
press button 34 to request breathing therapy (e.g., stimulation of
phrenic nerves 14 by IMD 10, such as during the next period of time
when the patient is sleeping).
[0071] It will be recognized that the diagrams of FIGS. 1-3 should
be taken as exemplary of the type of device in which various
embodiments described herein may be embodied, and not as limiting
to such devices. The processes described herein may be practiced in
a wide variety of device implementations, including pacemakers
(see, for example, FIG. 9), pacemaker-cardioverter-defibrillators,
etc. Alternatively, or in combination, such processes may be
carried out using implantable nerve stimulators or muscle
stimulators, and further, for example, with use of monitoring
devices (e.g., cardiac monitoring devices) that do not provide any
stimulation (e.g., a monitoring device may be used with a separate
stimulation device; such devices provided with a form of
communication therebetween).
[0072] A generalized method 200, for treating the symptoms of or
treating heart failure and/or hypertension, e.g., using diaphragm
contraction prolongation, is diagrammatically depicted in the flow
chart of FIG. 4. Method 200 (as well as one or more other methods
illustrated herein) are intended to illustrate the general
functional operation of the devices and/or systems, and should not
be construed as reflective of a specific form of software or
hardware necessary to practice all of the methods described herein.
It is believed that the particular form of software will be
determined primarily by the particular system architecture employed
in the device (e.g., IMD 10) and by the particular detection and
therapy delivery methodologies employed by the device and/or
system. Providing software and/or hardware to accomplish the
described methods in the context of any modern IMD, or devices
usable therewith, given the disclosure herein, is within the
abilities of one of skill in the art.
[0073] Further, methods described in conjunction with flow charts
presented herein may be implemented in a computer-readable medium
that includes instructions for causing a programmable processor to
carry out the methods described. A "computer-readable medium"
includes but is not limited to any volatile or non-volatile media,
such as a RAM, ROM, CD-ROM, NVRAM, EEPROM, flash memory, and the
like. The instructions may be implemented as one or more software
modules, which may be executed by themselves or in combination with
other software.
[0074] The hardware used to accomplish the described methods, may
include any one or more of a microprocessor, a digital signal
processor (DSP), a controller, an application specific integrated
circuit (ASIC), a field programmable gate array (FPGA), or
equivalent discrete or integrated logic circuitry. In one or more
exemplary embodiments, the processor may include multiple
components, such as any combination of one or more microprocessors,
one or more controllers, one or more DSPs, one or more ASICs, or
one or more FPGAs, as well as other discrete or integrated logic
circuitry. The functions and processes described herein may be
embodied as software, firmware, hardware, or any combination
thereof.
[0075] The term "module," "processor," or other like terminology,
may generally refer to any of the foregoing circuitry, alone or in
combination with other logic circuitry, or any other equivalent
circuitry. Such hardware, software, and/or firmware may be
implemented within the same device or within separate devices to
support the various operations and functions described in this
disclosure. In addition, any of the described units, modules, or
components may be implemented together or separately as discrete
but interoperable 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.
[0076] The method 200 of FIG. 4 includes a determination of the
presence of elevated sympathetic tone (block 202) based on, for
example, one or more physiological parameters such as an elevated
blood pressure. For example, the presence of elevated sympathetic
tone may be determined or detected in various manners. For example,
an elevated sympathetic tone may be determined based on one or more
monitored physiological parameters of a patient (e.g., at least one
physiological parameter) such as, for example, the electrical
activity of the patient or patient's heart, the chemical activity
of the patient or patient's heart, hemodynamic pressure of the
patient, etc. At least in one embodiment, elevated sympathetic tone
is determined based on elevated blood pressure (e.g., a patient
determined to have hypertension).
[0077] For example, the electrical activity of a patient may
include one or more signals that may be monitored (e.g., using
electrodes from locations in or around the patient's heart, or
other locations of the body, including outside of the body). Using
such monitored electrical activity, certain metrics may be
determined and collected (e.g., for analysis to determine a
sustained condition, a temporary condition, etc.). For instance,
the following metrics may be determined and collected using the
electrical activity of the patient: heart rate (HR), heart rate
variability (HRV), galvanic skin response (GSR), respiratory events
including breathing or respiratory rate (e.g., using impedance
measurements such as in impedance plethysmography), etc.
[0078] The chemical activity of a patient may include one or more
chemical properties that may be monitored (e.g., using various
sensors from locations in or around the patient's heart, or other
locations of the body, including outside of the body). Using such
monitored chemical activity, certain metrics may be determined and
collected (e.g., for analysis to determine a sustained condition, a
temporary condition, etc.). For instance, the following metrics may
be determined and collected using the chemical activity of the
patient's heart: oxygen saturation, lung fluid status, etc.
[0079] The hemodynamic activity of a patient may include one or
more hemodynamic pressures that may be monitored (e.g., using
various sensors from locations in or around the patient's heart or
other locations of the body, and/or in or around (e.g., outside of)
the patient's body). Using such monitored hemodynamic pressures of
a patient, certain metrics may be determined and collected (e.g.,
for analysis to determine a sustained condition, a temporary
condition, etc.). For instance, the following metrics may be
determined and collected using the hemodynamic pressures of the
patient (e.g., using an IMD 10 or other devices, such as, Medtronic
OptiVol Fluid Status Monitoring devices): mean arterial pressure,
diastolic blood pressure, systolic blood pressure, flow rates,
pressure drops, pulmonary artery pressure, pulmonary capillary
wedge pressure, right ventricular systolic pressure, right
ventricular diastolic pressure, changes in oxygen saturation of the
tissue or blood, changes in the amplitude or timing of heart
sounds, changes in intrathoracic impedance, changes in intracardiac
impedance, heart sounds, lung sounds, tissue perfusion,
intracardiac pressure, pulmonary vein pressure, cardiac imaging,
shear stress, partial pressure of oxygen, respiratory cycles (e.g.,
including respiratory events such as the start of the inspiration
phase, end of inspiration phase, or other respiratory waveform
events), etc.
[0080] The nerve activity of a patient may include one or more
signals monitored (e.g., using electrodes/sensors at locations in
or around the patient's heart or other locations of the body,
and/or from locations proximate patient's nerves). More
specifically, the electrical signals propagating along the one or
more nerve fibers innervating musculature of a patient may include
parasympathetic and sympathetic signals propagating along efferent
and afferent nerve fibers. For instance, metrics may be determined
and collected using the nerve activity monitoring, such as muscle
sympathetic nerve activity (MSNA).
[0081] In other words, an elevated sympathetic tone may be
determined based on one or more monitored physiological parameters
of a patient (e.g., at least one physiological parameter). For
example, the monitored physiological parameters may be indicative
of an elevated sympathetic tone. For example, an elevated
sympathetic tone may be determine based on the monitored one or
more physiological parameters in comparison to thresholds or
baselines provided or defined for a patient. For example, an
elevated sympathetic tone may be determined based on an at least
one of elevated blood pressure, an elevated heart rate, decreased
heart rate variability, decreased muscle sympathetic nerve
activity, a decreased galvanic skin response, and/or an increased
respiratory rate. At least in one embodiment, elevated sympathetic
tone is determined based on elevated blood pressure (e.g., a
patient determined to have hypertension).
[0082] Upon a determination that an elevated sympathetic tone
exists for a patient, a plurality of breathing therapy sessions are
provided (block 204). Such breathing therapy sessions may be part
of treatment plan (e.g., a scheduled plan, for example, defining a
plurality of breathing sessions for a patient and carried out under
control of the IMD 10).
[0083] In one or more embodiments, the plurality of breathing
therapy sessions (block 204) may include use of diaphragm
contraction prolongation. For example, the use of stimulation after
the start of the inspiration phase of the breathing cycle to
prolong diaphragm contraction during the breathing cycle.
[0084] One or more embodiments of providing such diaphragm
contraction prolongation are described in U.S. Pat. App. Pub. No.
US2007/0118183 to Gelfand et al., published May 24, 2007, and
entitled "System and Method to Modulate Phrenic Nerve to Prevent
Sleep Apnea," which describes treating breathing disorders such as
central sleep apnea using stimulation provided to the phrenic nerve
through a transvenous lead system. U.S. Pat. App. Pub. No.
US2007/0118183 describes use of stimulation beginning after
inspiration to extend the duration of a breath and to hold the
diaphragm in a contracted condition (e.g., prolong diaphragm
contraction).
[0085] In one or more embodiments to provide diaphragm contraction
prolongation for breathing therapy as described herein, the
respiratory cycle of a patient is monitored using one or more
physiological parameters, such as impedance and/or pressure
measurements. For example, respiratory monitoring is described in
U.S. Pat. No. 7,623,917 to Cho et al., issued Nov. 24, 2009,
entitled "Method of Optimizing Data Collection and Therapy Delivery
Based on Respiration," which is incorporated herein in its
entirety.
[0086] As described in U.S. Pat. No. 7,623,917, hemodynamic
parameters may be used in accordance with various embodiments to
monitor the respiratory cycle (e.g., determine breathing cycle
events such as the start of the inspiration phase). For example,
right ventricular pressure (RVP) and/or left ventricular pressure
(LVP) acquired during respiration in a patient may be collected via
pressure sensors (e.g., at sample rates as high as 256 Hz or
higher) and respiration waveforms may be derived therefrom. For
example, the RVP and/or LVP signals, respectively, may be passed
through a low-pass filter (e.g., such that higher frequency
components may be filtered out or removed) according to one or more
embodiments. Further, for example, the respiratory cycle may be
derived based on either RVP or LVP, or a combination thereof.
[0087] The respiratory cycle derived from the pressure measurements
may be used to provide the two relatively distinct phases of the
respiratory cycle, i.e., the inspiration phase and the expiration
phase, as well as respiratory rate. Various phase events are
present in a respiratory cycle, such as the start of the
inspiration phase, the end of the inspiration phase, the start of
the expiration phase, and the end of the expiration phase. Further,
it may be desirable to have multiple timing reference points
defined within a given respiratory cycle, or within one or both of
the inspiration and expiration phases. For example, it may be
desirable to define the start or the end of the inspiration phase,
and/or points in the respiratory cycle, such as for use in
delivering stimulation at one or more times during the respiratory
or breathing cycle.
[0088] Still further, for example, the respiratory cycle may be
derived from impedance measurements made using multiple electrodes
(e.g., an electrode on a lead and a can electrode provided as part
of the IMD 10). For example, an electrode on a lead may cooperate
with an indifferent electrode on the can of the IMD 10 to source
and sink low amplitude electrical pulses that are used to track
changes in lung volume over time (e.g., based on impedance). This
may be referred to as impedance plethysmography and may also be
used to derive the inspiration and expiration events of an
individual breath, as well as to track breathing rate.
[0089] Still further, other types of respiration sensing may also
be used. For example, a sensor for measuring chest movement (e.g.,
a sensor outside the patient's body) such as with a respiration
belt may be used, or a thermistor based system may be used.
Impedance type respiratory tracking, pressure based respiratory
tracking, or any other respiratory tracking process, may be used
alone or in combination to derive the respiratory or breathing
cycle. Such processes can measure the respiration of the patient
and the resulting respiration data may be collected over periods of
time (e.g., data over minutes, hours, and days can be logged),
transmitted, and/or used to direct the breathing therapy.
[0090] With the respiratory cycle of a patient derived, stimulation
may be timed to provide for diaphragm contraction prolongation. For
example, when a breathing therapy session is implemented over a
plurality of breathing cycles, stimulation is used to prolong
diaphragm contraction. For example, the stimulation (e.g., of the
phrenic nerve) may occur at a time after the beginning or start of
the inspiration phase. In one or more embodiments, the stimulation
may begin after the onset of exhalation or expiration. Any suitable
shape of stimulation pulse and/or amplitude thereof may be used to
provide the stimulation. However, when delivered, stimulation is
provided such that the stimulation "stills" the diaphragm resulting
in an amount of air trapped in at least one lung and extends the
breath duration. In other words, suitable stimulation initiated
after inspiration can "prolong" or "hold" the breath, and thus
regulate breathing.
[0091] With further reference to FIG. 4, the plurality of breathing
therapy sessions may be provided in one or more different manners.
For example, in one or more embodiments, breathing therapy sessions
may be activated one or more times a day (i.e., 24 hour period)
with a predetermined duration (e.g., minutes, hours, etc.).
Further, for example, in one or more embodiments, one or more
breathing therapy sessions may be activated during each of one or
more days.
[0092] Such breathing therapy sessions may be of any number and
each of such breathing sessions may be of any duration. In other
words, the type of breathing sessions used to train an individual
to breath slower will, at least in part, be determined on a patient
by patient basis. For example, a patient with a temporary elevated
sympathetic tone may be scheduled with different breathing therapy
sessions than a person with a chronic sustained condition. For
example, a 30 minute session, once a day for several weeks, may be
effective for a patient with a temporary elevated sympathetic tone,
whereas, 2 to 3 breathing therapy sessions per day for months may
be needed to provide an effect in a patient with a sustained or
chronic elevated sympathetic tone.
[0093] In one or more embodiments, the breathing therapy sessions
are scheduled and/or carried out when a patient is not cognitive of
respiratory control (e.g., when the patient is breathing
autonomously). For example, breathing therapy sessions may be
carried out with a patient, such as a quadraplegic patient (e.g.,
who has lost respiratory sensation and is not cognitive of
respiratory control), for the purpose of attempting to train the
patient to control breathing (e.g., such sessions may be carried
out when the patient is awake). Further, in one or more
embodiments, the breathing therapy sessions may be carried out when
a patient is asleep and is not cognizant of their respiratory
control.
[0094] As shown in FIG. 7, an activity detection method 250 may be
used in combination with one or more breathing therapy processes
described herein (e.g., breathing therapy process 200 as shown
generally in FIG. 4). For example, the method 250 may include
determining whether the patient is awake or sleeping (e.g., a
substantially reduced level of activity) (block 252) prior to
activating a breathing therapy session. Such a determination may be
implemented with the use of an activity sensor (e.g., an
accelerometer), posture sensor, etc. For example, if the patient
exhibits a higher level of activity (e.g., relative to a baseline
or threshold), activation of a breathing therapy session may be
delayed (block 254). Further, for example, if the patient exhibits
a lower level of activity (e.g., relative to a baseline or
threshold, or indicative of a sleeping state), a breathing therapy
session may be activated (block 254).
[0095] In one or more embodiments, for example, a breathing therapy
session may be scheduled to be carried out during a particular
time. If it is determined that the patient is awake during this
particular scheduled time, then the breathing therapy session may
be delay (e.g., the schedule may be adjusted, activity level may be
checked continuously over a period of time until the therapy
session may be activated, etc.). Further, in one or more
embodiments, for example, a breathing therapy session may be
activated upon a determination that the patient is asleep (e.g.,
each day, when a person is first determined to be asleep, a
breathing therapy session is activated).
[0096] The breathing therapy method 200 of FIG. 4 may be
implemented as an open loop control process. For example, upon a
determination that a patient exhibits elevated sympathetic tone
(block 202) (e.g., exhibits hypertension or high blood pressure), a
breathing therapy may be defined for the patient. For example, a
pre-programmed breathing therapy protocol may be implemented for
the patient (e.g., carried out by the IMD 10) using respiratory
sensing to time stimulation. For example, one or more breathing
therapy sessions per day may be scheduled with such sessions each
being carried out for a predetermined period of time (e.g., one
session a day for 30-60 minutes). One will recognize that such a
session may be delayed depending on a determination of whether the
patient is asleep when the session is scheduled. In other words,
the pre-programmed diaphragm contraction prolongation protocol
(e.g., over a plurality of breathing therapy sessions) may be
carried out regulate the breathing pattern of the patient (e.g., to
train the patient to breath slower over time).
[0097] Further, in one or more embodiments, breathing therapy may
be implemented as a closed loop control process as shown by the
breathing therapy method 300 of FIG. 5. For example, upon a
determination that a patient exhibits elevated sympathetic tone
(block 302), a breathing therapy may be defined for the patient
which may include a plurality of breathing sessions 304 to be
carried out. For example, a breathing therapy protocol may be
implemented for the patient (e.g., to be carried out by the IMD 10)
using respiratory sensing to time stimulation.
[0098] However, unlike the open loop process, one or more
physiological parameters of a patient are monitored to determine a
change in the elevated sympathetic tone and one or more
characteristics of one or more breathing therapy sessions may be
adjusted based thereon. For example, the physiological parameters
used to determine that a patient exhibits an elevated sympathetic
tone, or any other patient physiological parameters, may be
monitored (block 306) and used as feedback to adjust one or more
parameters of the plurality of breathing sessions (block 308)
(e.g., such that therapy is continued and adjusted until a defined
target for one or more of the physiological parameters is reached).
For example, the number of breathing therapy sessions per day may
be changed, the duration of such sessions may be changed,
additional breathing therapy sessions may be scheduled and/or
carried out, target breathing cycle lengths may be adjusted, etc.
Further, for example, once the defined target level for one or more
the physiological parameters (e.g., such as those used to determine
an elevated sympathetic tone for the patient, or any other patient
parameters) being monitored (block 306) has been reached, the
breathing therapy may be terminated (block 310).
[0099] For example, in one embodiment, blood pressure (e.g.,
indicative of hypertension) may be used to determine an elevated
sympathetic tone for a patient (e.g., the blood pressure may be
elevated relative to a baseline or target pressure). In such a
case, in the closed loop system, blood pressure may continuously be
monitored to determine a change therein. Such monitoring of the
blood pressure may be used as feedback for adjusting one or more
characteristics of one or more breathing therapy sessions (e.g.,
until a defined target blood pressure is reached).
[0100] It will be recognized that such monitoring of one or more
physiological parameters of a patient may be used as feedback
between breathing therapy sessions (e.g., to modify one or more
parameters of a subsequent breathing therapy session) or within a
breathing therapy session (e.g., to modify one or more parameters
of a session currently being carried out).
[0101] In one or more embodiments, a breathing therapy session may
be implemented as shown by the method 350 of FIG. 6. For example,
each of the plurality of breathing therapy sessions or diaphragm
contraction prolongation (DCP) therapy sessions may include
determining a current breathing cycle length for the patient (e.g.,
derived from the current breathing rate) and a duration of the
inspiration phase of a current breathing cycle (block 362) upon
activation of the session (block 360). With a target cycle length
being set for the patient (e.g., predefined, defined based on
current breathing cycle length, etc.), the current breathing rate
is monitored (e.g., current breathing rate detected is compared to
the target breathing rate) (block 364) and stimulation delivered to
prolong diaphragm contraction to increase the breathing rate cycle
length until the target cycle length is attained (e.g., delivering
stimulation after the start of the inspiration phase of each of a
plurality of breathing cycles to provide an increasing diaphragm
contraction prolongation over the plurality of breathing cycles
until the target breathing cycle length of the patient is attained)
(block 368). For example, the duration of the stimulation delivered
over the plurality of breathing cycles may follow an increasing
linear function to provide an increasing breathing cycle
length.
[0102] Once the current breathing cycle length is equal to the
target cycle length (block 364), then stimulation is continued to
maintain the target breathing cycle length of the patient (e.g.,
after the target breathing cycle length is attained, the
stimulation amplitude or duration which allowed the patient to
attain the target breathing length is maintained) (block 366). It
is noted that if the current breathing rate should fall below the
target breathing rate during attempts to maintain the target, the
process shown by blocks 364, 368 may be repeated to get back to the
target breathing rate. Further, for example, stimulation after the
target breathing cycle length of the patient is attained may be
continued until the end of the predefined time period for the
breathing therapy session (block 370). In other words, if the
duration of the current breathing therapy session is less than a
session timeout threshold (block 370) (e.g., the predetermined time
for the session has not yet expired), then stimulation to maintain
the target breathing cycle length is continued (block 366).
However, if the duration of the current breathing therapy session
is equal to the session timeout threshold (block 370), then
stimulation for this session is terminated (block 372).
[0103] For example, the diaphragm contraction prolongation (DCP)
sessions or breathing therapy sessions may be activated one or more
times during the day (i.e., 24 hours) and continued for a
predetermined duration (e.g., 15-30 minutes). During the breathing
therapy session, one or more respiration sensors (e.g., impedance,
pressure, chest movement, etc.) may be employed to monitor
respiration phases, rate, and tidal volume. For example, when the
breathing rate is higher than a predetermined threshold (e.g. 8
cycles/min or 7.5 sec/cycle) which may be indicative of an elevated
sympathetic tone, one or more breathing therapy sessions may be
implemented, e.g., using stimulation to provide diaphragm
contraction prolongation, such as stimulation applied after the
start of the inspiration phase and 50-100 ms before the estimated
termination of inspiration phase.
[0104] For example, to carry out the stimulation, the inspiration
phase of the respiratory cycle may be estimated based on the mean
value of prior breathing cycles (e.g., three prior breathing cycles
or in some other programmable manner). The estimated inspiration
phase may then be used to time the stimulation. For example, the
duration of the DCP stimulation can follow a linear function to
increase the breathing cycle. In other words, in one exemplary
embodiment, for example, if the breathing cycle length is 4
seconds, inspiration phase is 2 seconds, and the target cycle
length is 7.5 seconds, then DCP duration, Y(t)=mX(t)+b, where X(t)
is the inspiration phase length at time t, and m (m<1), b are
programmable parameters, is increased until the breathing cycle
length reaches its target value of 7.5 seconds. Once the current
breathing cycle length reaches the target value, Y(t) is constant
as long as the cycle length does not change by a preset tolerance
boundary (+/-10%) until the breathing therapy session duration
expires.
[0105] One will recognize that the duration or other parameters of
the stimulation may follow some other function besides a linear
function to increase breathing cycle length. For example, such
stimulation may use a larger increase in stimulation duration early
in the breathing therapy session as opposed to later in the session
(e.g., a non-linear function), such stimulation may be adjusted in
amplitude to achieve an increase in breathing rate, etc.
Stimulation waveforms may be varied in amplitude and duration to
adjust therapy. Further, the time of application of the stimulation
within the breathing cycle may also be adjusted to control
prolongation.
[0106] Further, in one or more embodiments, a breathing therapy
session may be implemented as shown by the method 400 of FIG. 8
wherein pacing therapy based on one or more respiratory
characteristics may be used (block 404) in combination with
diaphragm contraction prolongation therapy (406) during an
initiated breathing therapy session (block 404). Such pacing
therapy may be used during a part of the session, throughout the
entire session, periodically during the session, etc., or until the
breathing therapy session is terminated (block 408). For example,
such pacing and breathing therapy may be implemented using an IMD
generally shown herein with reference to FIGS. 1-3 and/or an IMD 90
as shown and described with reference to FIG. 9. Such a combination
therapy may, for example, provide benefits for patients with
chronotropic incompetence (e.g., the inability of the heart to
increase its rate with increased activity), or any other patients
with an elevated sympathetic tone.
[0107] For example, FIG. 9 is a block diagram illustrating
constituent components of the exemplary IMD 90. IMD 90 may be a
pacemaker having a microprocessor-based architecture. For the sake
of convenience, IMD 90 in FIG. 9 is shown with only a single lead
92 connected thereto. IMD 90 may include any number of leads 92 to
which similar circuitry and connections not explicitly shown in
FIG. 9 may apply. For example, in one embodiment, leads 92 may
correspond to leads 16 of FIGS. 1-2.
[0108] As shown in FIG. 9, lead(s) 92 are coupled to node 94 in IMD
90 through input capacitor 95. Input/output circuits 96 contain
analog circuits for interfacing to lead 92 and circuits for the
application of stimulation to one or both of phrenic nerves 14 and,
in some embodiments, the heart 20 of patient 12. The delivery of
stimulation to phrenic nerves 14 may be controlled by
software-implemented algorithms stored within microcomputer circuit
98. In embodiments where IMD 90 is also used to pace heart 20,
software-implemented algorithms stored within microcomputer circuit
98 may also control the rate of heart 20.
[0109] Microcomputer circuit 98 preferably comprises on-board
circuit 100 and off-board circuit 102. On-board circuit 100
preferably includes microprocessor 104, system clock circuit 106
and on-board RAM 108 and ROM 110. Off-board circuit 102 preferably
comprises a RAM/ROM unit. On-board circuit 100 and off-board
circuit 102 are each coupled by data communication bus 112 to
digital controller/timer circuit 114. Microcomputer circuit 98 may
comprise a custom integrated circuit device augmented by standard
RAM/ROM components.
[0110] Operating commands for controlling the delivery of
stimulation by IMD 90 are coupled by data bus 112 to digital
controller/timer circuit 114. For example, software-implemented
algorithms stored within microcomputer circuit 98 may cause
processor 104 to direct digital controller/timer circuit 114 via
data bus 112 to cause the stimulation of phrenic nerves 14 in
response to a signal indicating activation of breathing therapy.
Where IMD 90 is used to pace heart 20, digital timers and counters
of digital controller/timer circuit 114 establish the overall
escape interval of the IMD 90, as well as various refractory,
blanking and other timing windows for controlling the operation of
peripheral components disposed within input/output circuits 96.
[0111] Digital controller/timer circuit 114 may be coupled to
sensing circuitry, including sense amplifier 116, peak sense and
threshold measurement unit 118 and comparator/threshold detector
120. Circuit 114 may also be coupled to electrogram (EGM) amplifier
124 for receiving amplified and processed signals sensed by lead
92. The electrogram signal provided by EGM amplifier 124 is
employed when IMD 90 is being interrogated by an external
programmer to transmit a representation of a cardiac analog
electrogram. The electrogram signal may also be converted to a
digital signal by ADC and multiplexer circuit 138 and provided
microcomputer circuit 98 for digital signal analysis by
microprocessor 104, which may, for example, analyze the signal for
one or more purposes.
[0112] Sense amplifier 116 amplifies sensed electrical cardiac
signals and provides an amplified signal to peak sense and
threshold measurement circuitry 118, which in turn provides an
indication of peak sensed voltages and measured sense amplifier
threshold voltages on multiple conductor signal path 122 to digital
controller/timer circuit 114. An amplified sense amplifier signal
is then provided to comparator/threshold detector 120. Sense
amplifier 116, peak sense and threshold measurement unit 118 and
comparator/threshold detector 120 may be used by circuit 114 to
detect intrinsic events within heart 20, such as depolarizations or
repolarizations of atria or ventricles.
[0113] Output pulse generator 126 provides stimulation to phrenic
nerves 14 through coupling capacitor 128 in response to signals
provided by digital controller/timer circuit 114. Signals provided
by digital controller/timer circuit 114 may control the amplitude,
and other characteristics of the phrenic stimulation. High
amplitude pulses may be provided by output pulse generator 126 in
order to ensure capture of phrenic nerves 14 and adequate
contraction prolongation of diaphragm 18.
[0114] Digital controller/timer circuit 114 may also control the
timing of stimulation of phrenic nerves 14, as well as cardiac
pacing pulses. Circuit 114 may cause output pulse generator to
deliver stimulation based on detected respiratory and/or intrinsic
cardiac events. Where IMD 90 also paces heart 20 via output pulse
generator 126, output pulse generator 126 may provide pacing
stimuli to heart 20 through coupling capacitor 98 in response to a
pacing trigger signal provided by digital controller/timer circuit
114 each time the escape interval times out, an externally
transmitted pacing command is received or in response to other
stored commands as is well known in the pacing art. Circuit 114 may
direct output pulse generator 126 to increase the amplitude of
pacing pulses in order to stimulate phrenic nerves 14, as described
above. In some embodiments, IMD 90 may include separate leads 92,
sensing circuitry 116-120, and output pulse generators 126 for
cardiac pacing, and leads 92 and output pulse generators 126 for
delivering stimulation to phrenic nerves 14.
[0115] Electrical components shown in FIG. 9 are powered by an
appropriate implantable battery power source 130 in accordance with
common practice in the art. For the sake of clarity, the coupling
of battery power to the various components of IMD 90 is not shown
in the FIG. 9. VREF and Bias circuit 132 most preferably generates
stable voltage reference and bias currents for analog circuits
included in input/output circuit 96.
[0116] Antenna 134 is connected to input/output circuit 96 to
permit uplink/downlink telemetry through RF transmitter and
receiver telemetry unit 136. Telemetry unit 136 may receive a
signal indicating a need for breathing therapy from patient
activator 32 (FIG. 1) via antenna 134. Further, IMD 90 may be
programmable by means of an external programming unit (not shown)
via antenna 134 and telemetry unit 136.
[0117] IMD 90 may include activity sensor or accelerometer 140.
Activity sensor 140 typically (although not necessarily) provides a
sensor output that varies as a function of a measured parameter
relating to a patient's metabolic requirements. The output signal
provided by activity sensor 140 is coupled to input/output circuit
96. Microprocessor 104 may receive the output signal provided by
activity sensor 140, and determine whether a person is inactive
(e.g., asleep). For example, microprocessor 104 may compare the
output signal to one or more threshold values stored in one of
memories 102, 108 and 110.
[0118] Although FIG. 9 is a block diagram illustrating constituent
components of a pacemaker, it will be recognized that a
pacemaker-cardioverter-defibrillator (PCD) having a
microprocessor-based architecture may also be used to carry out
breathing therapy (e.g., including DCP and cardiac pacing), along
with carrying out additional functionality typically provided by a
PCD.
[0119] Where IMD 90 is used to pace heart 20, circuit 114 may
include programmable digital counters which control the basic time
intervals associated with DDD, VVI, DVI, VDD, AAI, DDI and other
modes of single, dual and three chamber pacing well known to the
art. For example, circuit 114 may control the time intervals
associated with biventricular cardiac resynchronization therapy.
Circuit 114 may also control escape intervals associated with
anti-tachyarrhythmia pacing in right atrium 24, right ventricle 26,
and/or left ventricle 28, employing any anti-tachyarrhythmia pacing
therapies known to the art.
[0120] In further reference to FIG. 8, the cardiac pacing used
during breathing therapy sessions (block 404) along with diaphragm
contraction prolongation therapy (block 406) may be delivered in
various manners. Such cardiac pacing may include atrial,
ventricular or bi-ventricular pacing, to mimic the respiratory
sinus arrhythmia.
[0121] In one or more embodiments, for example, cardiac pacing may
be delivered to the patient based on a predefined ratio of
breathing rate to heart rate. For example, a set of predefined
ratios may be used to pace the heart during delivery of diaphragm
contraction prolongation therapy as the breathing cycle length is
increased, or maintained at a target length. For example, such
ratios of breathing rate to heart rate ratios may include 1:4, 1:5,
1:6, etc. In other words, for example, the heart may be paced to
accomplish 5 beats per breath, 6 beats per breath, etc.
[0122] Further, in one or more embodiments, for example, cardiac
pacing may be delivered to the patient based on a predefined ratio
of inspiration pacing rate to expiration pacing rate. For example,
a set of predefined ratios may be used to pace the heart during
delivery of diaphragm contraction prolongation therapy as the
breathing cycle length is increased, or maintained at a target
length. For example, such ratios of inspiration pacing rate to
expiration pacing rate may include 3:1; 3:2, 2:1, etc. In other
words, for example, if the heart is to be paced at 8 beats per
breath, the heart may be paced to accomplish 6 beats within the
expiration phase and 2 beats in the inspiration phase when the
ratio of 3:1 is used to control such pacing.
[0123] Still further, for example, as shown by method 450 in FIG.
10, one or more additional breathing therapies may be used (block
456) in combination with diaphragm contraction prolongation (block
454) during an initiated breathing session (block 452). Such
therapies may be used during a part of the session, throughout the
entire session, periodically during the session, etc., or until the
breathing therapy session is terminated (block 458). For example,
such therapies may be implemented as described herein with
reference to FIG. 1. For example, such additional therapies may
include providing at least one of carotid sinus stimulation, aortic
baroreceptor stimulation, baroreflex activation therapy, vagus
nerve stimulation, spinal cord stimulation, renal nerve block, and
drug therapy.
[0124] All patents, patent documents, and references cited herein
are incorporated in their entirety as if each were incorporated
separately. This disclosure has been provided with reference to
illustrative embodiments and is not meant to be construed in a
limiting sense. As described previously, one skilled in the art
will recognize that other various illustrative applications may use
the techniques as described herein to take advantage of the
beneficial characteristics of the apparatus and methods described
herein. Various modifications of the illustrative embodiments, as
well as additional embodiments of the disclosure, will be apparent
upon reference to this description.
* * * * *