U.S. patent application number 16/752363 was filed with the patent office on 2020-09-10 for evaluating stimulation eficacy for treating sleep apnea and lingual muscle tone sensing system for improved osa therapy.
The applicant listed for this patent is Medtronic Xomed, LLC. Invention is credited to Rebecca Haag, James Hissong, Avram Scheiner, Randal Schulhauser, Erik Scott.
Application Number | 20200282215 16/752363 |
Document ID | / |
Family ID | 1000004672202 |
Filed Date | 2020-09-10 |
United States Patent
Application |
20200282215 |
Kind Code |
A1 |
Scheiner; Avram ; et
al. |
September 10, 2020 |
EVALUATING STIMULATION EFICACY FOR TREATING SLEEP APNEA AND LINGUAL
MUSCLE TONE SENSING SYSTEM FOR IMPROVED OSA THERAPY
Abstract
A system and method of assessing therapy of an implantable
neurostimulator (INS), the INS including a lead having at least one
pair of bi-polar electrodes, and a pulse generator in electrical
communication with the bi-polar electrodes, the pulse generator
including a sensor, a memory, a control circuit, and a telemetry
circuit. The system and method includes an external programmer in
communication with the INS via the telemetry circuit, a server in
communication with the external programmer and including thereon an
application configured to receive sensor data from the INS from the
external programmer and assess a quality of the sleep of a patient
in which the INS is implanted based on the received sensor data,
and a remote computer in communication with the server and
configured to present an assessment of the quality of sleep of the
patient.
Inventors: |
Scheiner; Avram; (Vadnais
Heights, MN) ; Schulhauser; Randal; (Phoenix, AZ)
; Hissong; James; (Jacksonville, FL) ; Scott;
Erik; (Maple Grove, MN) ; Haag; Rebecca;
(Broomfield, CO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Medtronic Xomed, LLC |
Jacksonville |
FL |
US |
|
|
Family ID: |
1000004672202 |
Appl. No.: |
16/752363 |
Filed: |
January 24, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62814398 |
Mar 6, 2019 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61N 1/37252 20130101;
A61N 1/36078 20130101; A61N 1/36139 20130101; A61N 1/36003
20130101 |
International
Class: |
A61N 1/36 20060101
A61N001/36; A61N 1/372 20060101 A61N001/372 |
Claims
1. An implantable neurostimulator (INS) comprising: an electrical
lead having formed thereon at least a pair of bi-polar electrodes,
wherein the electrical lead is configured for placement of the pair
of bi-polar electrodes proximate protrusor muscles of a patient and
configured to receive electromyography (EMG) signals; a pulse
generator electrically connected to the electrical lead and
configured to deliver electrical energy to the pair of bi-polar
electrodes, the pulse generator having therein a sensor and a
control circuit, wherein the sensor and control circuit are
configured to receive the EMG signals and determine a tonal state
of the protrusor muscles in which the lead is placed.
2. The implantable neurostimulator of claim 1, wherein the control
circuit is in electrical communication with a therapy delivery
circuit and causes the therapy delivery circuit to deliver
electrical energy to the bi-polar electrodes upon a determination
that the EMG signal is below a threshold value.
3. The implantable neurostimulator of claim 1, wherein the control
circuit is in electrical communication with a therapy delivery
circuit and causes the therapy delivery circuit to deliver
electrical energy to the bi-polar electrodes upon a determination
that the EMG signal is below a threshold value and a heart rate
detected by the sensor is below a threshold.
4. The implantable neurostimulator of claim 1, wherein the control
circuit is in electrical communication with a therapy delivery
circuit and causes the therapy delivery circuit to deliver
electrical energy to the bi-polar electrodes upon a determination
that the EMG signal is below a threshold value and a motion sensor
determines that the INS is not moving.
5. The implantable neurostimulator of claim 1, wherein the control
circuit is in electrical communication with a therapy delivery
circuit and causes the therapy delivery circuit to deliver
electrical energy to the bi-polar electrodes upon a determination
that the EMG signal is below a threshold value and an acoustic
sensor detects sounds consistent with snoring.
6. The implantable neurostimulator of claim 1, wherein the control
circuit is in electrical communication with a therapy delivery
circuit and causes the therapy delivery circuit to deliver
electrical energy to the bi-polar electrodes upon a determination
that the EMG signal is below a threshold value and a temperature
sensor detects a body temperature consistent with sleeping.
7. The implantable neurostimulator of claim 1, wherein the control
circuit is in electrical communication with a therapy delivery
circuit and causes the therapy delivery circuit to deliver
electrical energy to the bi-polar electrodes upon a determination
that the EMG signal is below a threshold value and a breathing rate
sensor detects a breathing rate consistent with sleeping.
8. A system comprising: an implantable neurostimulator (INS),
including a lead having at least one pair of bi-polar electrodes,
and a pulse generator in electrical communication with the bi-polar
electrodes, the pulse generator including a sensor, a memory, a
control circuit, and a telemetry circuit; an external programmer in
communication with the INS via the telemetry circuit; a server in
communication with the external programmer and including thereon an
application configured to receive sensor data from the INS from the
external programmer and assess a quality of the sleep of a patient
in which the INS is implanted based on the received sensor data;
and a remote computer in communication with the server and
configured to present an assessment of the quality of sleep of the
patient.
9. The system of claim 8, further comprising a user interface
presented on the external programmer and configured to receive a
variety of self-reported data entered by the patient.
10. The system of claim 9, wherein the application is further
configured to assess the quality of the sleep of a patient in which
the INS is implanted based on the received sensor data and the
self-reported data.
11. The system of claim 10, wherein the assessment of the quality
of sleep is presented in the form of a sleep score.
12. The system of claim 8, wherein the application is configured to
assess the quality of the sleep of a patient in which the INS is
implanted based on the received sensor data and self-reported data
entered via a user interface on the external programmer and to
determine an set of suggested updated stimulation parameters for
the INS.
13. The system of claim 12, wherein the received sensor data
includes one or more of a tonal state of protrusor muscles,
heartrate, blood pressure, blood oxygen saturation, patient
temperature, arousals, awakenings, and electromyography data.
14. The system of claim 12, wherein the updated stimulation
parameters are available of review, acceptance, modification, or
rejection on the remote computer.
15. The system of claim 14, wherein upon acceptance or modification
of the updated stimulation parameters, the updated stimulation
parameters are transmitted to the external programmer.
16. The system of claim 15, wherein the external programmer
transmits the updated stimulation parameters to the INS.
17. A method of providing feedback for an implantable
neurostimulator (INS), comprising: receiving sensor data from an
INS having at least one lead implanted in a protrusor muscle of a
patient; receiving self-reporting data entered via a user
interface; analyzing the sensor and self-reported data to determine
a sleep score; recording the sleep score; and presenting the sleep
score for analysis.
18. The method according to claim 17, further comprising providing
suggestions for updating stimulation parameters of the INS.
19. The method according to claim 18, further comprising updating
the INS with the updated stimulation parameters for application of
stimulation to the patient.
20. The method according to claim 19, further comprising analyzing
with an artificial intelligence the self-reported data and sensor
data to determine whether a reversion to the stimulation parameters
of the INS prior to the update is necessary.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to U.S. Provisional
Application No. 62/814,398 filed Mar. 6, 2019 and entitled
INTRAMUSCULAR HYPOGLOSSAL NERVE STIMULATION FOR OBSTRUCTIVE SLEEP
APNEA THERAPY, the entire contents of which are incorporated herein
by reference.
TECHNICAL FIELD
[0002] This disclosure relates to a medical device system and
method for therapeutic electrical stimulation of the hypoglossal
nerve for treatment of obstructive sleep apnea. More particularly
the disclosure relates to methods of measuring lingual muscle tone
and evaluating efficacy of stimulation therapy.
BACKGROUND
[0003] Implantable medical devices capable of delivering electrical
stimulation pulses have been proposed or are available for treating
a variety of medical conditions, such as cardiac arrhythmias and
chronic pain as examples. Obstructive sleep apnea (OSA), which
encompasses apnea and hypopnea, is a serious disorder in which
breathing is irregularly and repeatedly stopped and started during
sleep, resulting in disrupted sleep and reducing blood oxygen
levels. OSA is caused by complete or partial collapse of the
pharynx during sleep. In particular, muscles in a patient's mouth
and throat intermittently relax thereby obstructing the upper
airway while sleeping. Airflow into the upper airway can be
obstructed by the tongue or soft pallet moving to the back of the
throat and covering a smaller than normal airway. Loss of air flow
also causes unusual inter-thoracic pressure as a person tries to
breathe with a blocked airway. Lack of adequate levels of oxygen
during sleep can contribute to abnormal heart rhythms, heart
attack, heart failure, high blood pressure, stroke, memory problems
and increased accidents. Additionally, loss of sleep occurs when a
person is awakened during an apneic episode. Implantable medical
devices capable of delivering electrical stimulation pulses have
been proposed for treating OSA by electrically stimulating muscles
around the upper airway that may block the airway during sleep.
SUMMARY
[0004] One aspect of the disclosure is directed to an implantable
neurostimulator (INS) including: an electrical lead having formed
thereon at least a pair of bi-polar electrodes, where the
electrical lead is configured for placement of the pair of bi-polar
electrodes proximate protrusor muscles of a patient and configured
to receive electromyography (EMG) signals; a pulse generator
electrically connected to the electrical lead and configured to
deliver electrical energy to the pair of bi-polar electrodes, the
pulse generator having therein a sensor and a control circuit,
where the sensor and control circuit are configured to receive the
EMG signals and determine a tonal state of the protrusor muscles in
which the lead is placed. Other embodiments of this aspect include
corresponding computer systems, apparatus, and computer programs
recorded on one or more computer storage devices, each configured
to perform the actions of the methods and systems described
herein.
[0005] Implementations of this aspect of the disclosure may include
one or more of the following features. The implantable
neurostimulator where the control circuit is in electrical
communication with a therapy delivery circuit and causes the
therapy delivery circuit to deliver electrical energy to the
bi-polar electrodes upon a determination that the EMG signal is
below a threshold value. The implantable neurostimulator where the
control circuit is in electrical communication with a therapy
delivery circuit and causes the therapy delivery circuit to deliver
electrical energy to the bi-polar electrodes upon a determination
that the EMG signal is below a threshold value and a heart rate
detected by the sensor is below a threshold. The implantable
neurostimulator where the control circuit is in electrical
communication with a therapy delivery circuit and causes the
therapy delivery circuit to deliver electrical energy to the
bi-polar electrodes upon a determination that the EMG signal is
below a threshold value and a motion sensor determines that the INS
is not moving. The implantable neurostimulator where the control
circuit is in electrical communication with a therapy delivery
circuit and causes the therapy delivery circuit to deliver
electrical energy to the bi-polar electrodes upon a determination
that the EMG signal is below a threshold value and an acoustic
sensor detects sounds consistent with snoring. The implantable
neurostimulator where the control circuit is in electrical
communication with a therapy delivery circuit and causes the
therapy delivery circuit to deliver electrical energy to the
bi-polar electrodes upon a determination that the EMG signal is
below a threshold value and a temperature sensor detects a body
temperature consistent with sleeping. The implantable
neurostimulator where the control circuit is in electrical
communication with a therapy delivery circuit and causes the
therapy delivery circuit to deliver electrical energy to the
bi-polar electrodes upon a determination that the EMG signal is
below a threshold value and a breathing rate sensor detects a
breathing rate consistent with sleeping.
[0006] A further aspect of the disclosure is directed to a system
including: an implantable neurostimulator (INS), including a lead
having at least one pair of bi-polar electrodes, and a pulse
generator in electrical communication with the bi-polar electrodes,
the pulse generator including a sensor, a memory, a control
circuit, and a telemetry circuit; an external programmer in
communication with the INS via the telemetry circuit; a server in
communication with the external programmer and including thereon an
application configured to receive sensor data from the INS from the
external programmer and assess a quality of the sleep of a patient
in which the INS is implanted based on the received sensor data;
and a remote computer in communication with the server and
configured to present an assessment of the quality of sleep of the
patient. Other embodiments of this aspect include corresponding
computer systems, apparatus, and computer programs recorded on one
or more computer storage devices, each configured to perform the
actions of the methods and systems described herein.
[0007] Implementations of this aspect of the disclosure may include
one or more of the following features. The system further including
a user interface presented on the external programmer and
configured to receive a variety of self-reported data entered by
the patient. The system where the application is further configured
to assess the quality of the sleep of a patient in which the INS is
implanted based on the received sensor data and the self-reported
data. The system where the assessment of the quality of sleep is
presented in the form of a sleep score. The system where the
application is configured to assess the quality of the sleep of a
patient in which the INS is implanted based on the received sensor
data and self-reported data entered via a user interface on the
external programmer and to determine a set of suggested updated
stimulation parameters for the INS. The system where the received
sensor data includes one or more of a tonal state of protrusor
muscles, heartrate, blood pressure, blood oxygen saturation,
patient temperature, arousals, awakenings, and electromyography
data. The system where the updated stimulation parameters are
available of review, acceptance, modification, or rejection on the
remote computer. The system where upon acceptance or modification
of the updated stimulation parameters, the updated stimulation
parameters are transmitted to the external programmer. The system
where the external programmer transmits the updated stimulation
parameters to the INS.
[0008] Still a further aspect of the disclosure is directed to a
method of providing feedback for an implantable neurostimulator
(INS), including receiving sensor data from an INS having at least
one lead implanted in a protrusor muscle of a patient. The method
also includes receiving self-reporting data entered via a user
interface. The method also includes analyzing the sensor and
self-reported data to determine a sleep score. The method also
includes recording the sleep score. The method also includes
presenting the sleep score for analysis. Other embodiments of this
aspect include corresponding computer systems, apparatus, and
computer programs recorded on one or more computer storage devices,
each configured to perform the actions of the methods and systems
described herein.
[0009] Implementations of this aspect of the disclosure may include
one or more of the following features. The method further including
providing suggestions for updating stimulation parameters of the
INS. The method further including transmitting updated stimulation
parameters to an external programmer associated with the INS and
updating the INS. The method further including analyzing with an
artificial intelligence the self-reported data and sensor to
determine whether a reversion to the stimulation parameters of the
INS prior to the update is necessary. Implementations of the
described techniques may include hardware, a method or process, or
computer software on a computer-accessible medium, including
software, firmware, hardware, or a combination of them installed on
the system that in operation causes or cause the system to perform
the actions. One or more computer programs can be configured to
perform particular operations or actions by virtue of including
Instructions that, when executed by data processing apparatus,
cause the apparatus to perform the actions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a conceptual diagram of an implantable
neurostimulator (INS) for delivering OSA therapy;
[0011] FIG. 2 is a conceptual diagram of a pulse generator included
in INS of FIG. 1;
[0012] FIG. 3 is a diagram of the distal portion of the lead of the
INS of FIG. 1 deployed for delivering OSA therapy according to one
aspect of the disclosure;
[0013] FIG. 4 is a diagram of the distal portion of a two lead INS
deployed for delivering OSA therapy according to a further aspect
of the disclosure;
[0014] FIG. 5 is a timing diagram illustrating a method performed
by the system of FIG. 1 for delivering selective stimulation to the
protrusor muscles for promoting upper airway patency during sleep
according to one example; and
[0015] FIG. 6 is a timing diagram of a method for delivering OSA
therapy by the system of FIG. 1 according to another example.
[0016] FIG. 7A depicts an electromyography plot of the tongue
compared to pharyngeal pressure during breathing;
[0017] FIG. 7B depicts the change in electromyography activity from
an awake to sleep state for both normal subjects and those
suffering from OSA;
[0018] FIG. 8 depicts electromyography of the tongue at different
sleep and wakefulness states;
[0019] FIG. 9 depicts steps of signal processing required to
transform raw electromyography signals into useable data streams in
accordance with the present disclosure;
[0020] FIG. 10 depicts a simplified system for collecting,
transmitting, and analyzing data derived from or directed to and
INS;
[0021] FIG. 11 depicts a flow chart for collecting, transmitting,
and analyzing data derived from or directed to and INS.
DETAILED DESCRIPTION
[0022] An implantable neurostimulator (INS) system for delivering
electrical stimulation to the lingual muscles of the tongue, in
particular the protrusor muscles, for the treatment of OSA is
described herein. Electrical stimulation is delivered to cause the
tongue of a patient to be in a protruded state, during sleep, to
avoid or reduce upper airway obstruction. As used herein, the term,
"protruded state" with regard to the tongue refers to a position
that is moved forward and/or downward compared to the
non-stimulated position or a relaxed position. Those of skill in
the art will recognize that to be in a protruded state does not
require the tongue to be coming out of the mouth of the patient,
indeed it is preferable that the tongue not extend out of the mouth
of the patient, but only be advanced forward to a point where
obstruction of the airway is mitigated or eliminated. The protruded
state is a state associated with the recruitment of protrusor
muscles of the tongue (also sometimes referred to as "protruder"
muscles of the tongue) including the genioglossus and geniohyoid
muscles. A protruded state may be the opposite of a retracted
and/or elevated position associated with the recruitment of the
retractor muscles, e.g., styloglossus and hyoglossus muscles, which
retract and elevate the tongue. Electrical stimulation is delivered
to cause the tongue to move to and maintain a protruded state to
prevent collapse, open or widen the upper airway of a patient to
promote unrestricted or at least reduced restriction of airflow
during breathing.
[0023] Current INS systems must be turned on and off manually by
the patient when they go to sleep and wake up. As will be
appreciated, manual switching is not always a desirable feature in
an implantable device associated with sleeping. In accordance with
one aspect of the disclosure the INS only need to be turned on when
there is a loss of lingual muscle tone (i.e., the protruder muscles
are not being sufficiently stimulated naturally). The loss of
lingual muscle tone increases the susceptibility of the patient to
experience an OSA event. Accordingly, one aspect of the disclosure
is directed to systems and methods for assessing the muscle tone of
the protruder muscles, based on the tonal state determining that
the patient is in need of therapy, and applying the needed therapy.
The result is a therapy system which will be more "natural" and
convenient for the patient and increase therapy compliance.
[0024] A further aspect of the disclosure is directed to systems
and methods of utilizing the sensed tonal state of the protrusor
muscles along with a variety of self-reported and detected patient
data to develop a patient feedback sleep score for consultation,
stimulation modification, and health care reimbursement
support.
[0025] FIG. 1 is a conceptual diagram of an implantable
neurostimulator (INS) system for delivering OSA therapy. The INS
system 10 includes at least one electrical lead 20 and a pulse
generator 12. Pulse generator 12 includes a housing 15 enclosing
circuitry including a control circuit, therapy delivery circuit,
optional sensor, a battery, and telemetry circuit as described
below in conjunction with FIG. 2. A connector assembly 17 is
hermetically sealed to housing 15 and includes one or more
connector bores for receiving at least one medical electrical lead
used for delivering OSA therapy and, in some examples, for sensing
physiological conditions such as electromyogram (EMG) signals and
the like. As depicted in FIG. 1 the pulse generator 12 is implanted
in the neck of the patient 8. The instant disclosure is not so
limited, and the pulse generator 12 may be located in other
locations such as in the chest area or other areas known to those
of skill in the art.
[0026] Lead 20 includes a flexible, elongate lead body 22 that
extends from a lead proximal end 24 to a lead distal end 26. At
least two electrodes 30 are carried along a lead distal portion
adjacent lead distal end 26 that are configured for insertion
within the protrusor muscles 42a, 42b and 46 of the patient's
tongue 40. The electrodes 30 are configured for implantation within
soft tissue such as musculature proximate to the medial branches of
one or both hypoglossal nerves (HGN) that innervate the protrusor
muscles of the tongue. The electrodes may be placed approximately 5
mm (e.g., from 2 mm to 8 mm) from a major trunk of the HGN. As
such, the electrodes 30 may be referred to herein as "intramuscular
electrodes," in contrast to an electrode that is placed on or along
a nerve trunk or branch, such as a cuff electrode, used to directly
stimulate the nerve trunk or branch. Lead 20 may be referred to
herein as an "intramuscular lead" since the lead distal end and
electrodes 30 are configured for advancement through the soft
tissue, which may include the protrusor muscle tissue, to anchor
electrodes 30 in proximity of the HGN branches that innervate the
protrusor muscles 42a, 42b and 46. The term "intramuscular" with
regard to electrodes 30 and lead 20 is not intended to be limiting,
however, since the electrodes 30 may be implanted in connective
tissue or other soft tissue proximate the medial HGN and its
branches. One or more electrodes 30 may be placed in an area of
protrusor muscles 42a, 42b and 46 that include motor points, where
each nerve axon terminates in the muscle (also called the
neuro-muscular junction). The motor points are not at one location
but spread out in the protrusor muscles. Leads 20 may be implanted
such that one or more electrodes 30 may be generally in the area of
the motor points (e.g., such that the motor points are within 1 to
10 mm from one or more electrodes 30).
[0027] The protrusor muscles are activated by electrical
stimulation pulses generated by pulse generator 12 and delivered
via the intramuscular electrodes 30 to move tongue 40 forward, to
promote a reduction in obstruction or narrowing of the upper airway
6 during sleep. As used herein, the term "activated" with regard to
the electrical stimulation of the protrusor muscles refers to
electrical stimulation that causes depolarization or an action
potential of the cells of the nerve (e.g., hypoglossal nerve(s))
innervating the protrusor muscles and motor points and subsequent
depolarization and mechanical contraction of the protrusor muscle
cells. In some cases, the muscles may be activated directly by the
electrical stimulation pulses. The protrusor muscles that may be
activated by stimulation via intramuscular electrodes 30 may
include at least one or both of the right and/or left genioglossus
muscle (GG) 42, which includes the oblique compartment (GGo) 42a
and the horizontal compartment (GGh) 42b (referred to collectively
as GG 42) and/or the right and/or left geniohyoid muscle (GH) 46.
The GG muscle and GH muscle are innervated by a medial branch of
the HGN (also referred to as the XIIth cranial nerve), while the
hyoglossus and styloglossus muscles, which cause retraction and
elevation of the tongue, are innervated by a lateral branch of the
HGN.
[0028] The multiple distal electrodes 30 may be used to deliver
bilateral or unilateral stimulation to the GG 42 and/or the GH 46
muscles via the medial branch of the HGN or branches thereof, also
referred to herein as the "medial HGN." Distal electrodes 30 may be
switchably coupled to output circuitry of pulse generator 12 to
enable delivery of electrical stimulation pulses in a manner that
selectively activates the right and left protrusor muscles in a
cyclical or alternating pattern to avoid muscle fatigue while
maintaining upper airway patency. Additionally or alternatively,
electrical stimulation may be delivered to selectively activate the
GG 42 and/or GH 46 muscles or portions thereof during unilateral
stimulation of the left or right protrusor muscles.
[0029] The lead proximal end 24 includes a connector (not shown in
FIG. 1) that is coupleable to connector assembly 17 of pulse
generator 12 to provide electrical connection between circuitry
enclosed by the housing 15 of pulse generator 12, e.g., including
therapy delivery circuitry and control circuitry as described below
in conjunction with FIG. 2. The lead body 22 encloses electrical
conductors extending from each of the distal electrodes 30 to the
proximal connector at proximal end 24 to provide electrical
connection between output circuitry of pulse generator 12 and the
electrodes 30.
[0030] Though shown in FIG. 1 as separate from and extending from
the pulse generator 12, the lead 20 could be integrated into a
portion of the pulse generator 12, and merely be an exposed surface
of the pulse generator 12. In such an embodiment, the pulse
generator would be implanted proximate the lingual muscles under
the chin of the patient. In contrast the embodiment shown in FIG. 1
allows for more flexibility in the placement of the pulse generator
in the neck or pectoral region of the patient.
[0031] FIG. 2 is a schematic diagram of pulse generator 12. Pulse
generator 12 includes a control circuit 80, memory 82, therapy
delivery circuit 84, a sensor 86, telemetry circuit 88 and power
source 90. Power source 90 may include one or more rechargeable or
non-rechargeable batteries for supplying electrical current to each
of the control circuit 80, memory 82, therapy delivery circuit 84,
sensor 86 and telemetry circuit 88. While power source 90 is shown
in communication only with control circuit 80 for the sake of
clarity, it is to be understood that power source 90 provides power
as needed to each of the circuits and components of pulse generator
12 as needed. For example, power source 90 provides power to
therapy delivery circuit 84 for generating electrical stimulation
pulses.
[0032] Sensor 86 may include one or more separate sensors for
monitoring a patient condition. These sensors may include one or
more accelerometers, inertial measurement units (IMU), fiber-Bragg
gratings (e.g., shape sensors), optical sensors, acoustic sensors,
pulse oximeters, and others without departing from the scope of the
disclosure and as will be described in greater detail below. In one
aspect of the disclosure sensor 86 is configured as, among other
things, a patient posture sensor. Patient posture data may be
stored in memory 82 from the detected posture states of patient
when sensor 86 is included, and may be presented on a display of
external programmer 50, e.g., as generally described in U.S. Pat.
No. 9,662,045 (Skelton, et al.), incorporated by reference in its
entirety.
[0033] Additionally or alternatively, the sensor 86 may detect a
signal that is correlated to the movement of the patient's tongue
into and out of a protruded state. This signal may be used to
detect adequate protrusion and/or fatigue of the stimulated muscle
for use in controlling the duty cycle, pulse amplitude and/or
stimulating electrode vector of the electrical stimulation therapy
delivered by therapy delivery circuit 84.
[0034] The functional blocks shown in FIG. 2 represent
functionality included in a pulse generator 12 configured to
delivery an OSA therapy and may include any discrete and/or
integrated electronic circuit components that implement analog
and/or digital circuits capable of producing the functions
attributed to a pulse generator herein. The various components may
include an application specific integrated circuit (ASIC), an
electronic circuit, a processor (shared, dedicated, or group) and
memory that execute one or more software or firmware programs, a
combinational logic circuit, state machine, or other suitable
components or combinations of components that provide the described
functionality. Providing software, hardware, and/or firmware to
accomplish the described functionality in the context of any modern
medical device system, given the disclosure herein, is within the
abilities of one of skill in the art.
[0035] Control circuit 80 communicates, e.g., via a data bus, with
memory 82, therapy delivery circuit 84, telemetry circuit 88 and
sensor 86 (when included) to control OSA therapy delivery and other
pulse generator functions. As disclosed herein, control circuit 80
may pass control signals to therapy delivery circuit 84 to cause
therapy delivery circuit 84 to deliver electrical stimulation
pulses via electrodes 30 according to a therapy protocol that may
include selective stimulation patterns of right and left portions
of the GG and GH muscles and/or proximal and distal portions of the
GG and GH muscles. Control circuit 80 may further be configured to
pass therapy control signals to therapy delivery circuit 84
including stimulation pulse amplitude, stimulation pulse width,
stimulation pulse number and frequency of a stimulation pulse
train.
[0036] Memory 82 may store instructions for execution by a
processor included in control circuit 80, stimulation control
parameters, and other device-related or patient-related data.
Control circuit 80 may retrieve therapy delivery control parameters
and a therapy delivery protocol from memory 82 to enable control
circuit 80 to pass control signals to therapy delivery circuit 84
for controlling the OSA therapy. Memory 82 may store historical
data relating to therapy delivery for retrieval by a user via
telemetry circuit 88. Therapy delivery data or information stored
in memory 82 may include therapy control parameters used to deliver
stimulation pulses as well as delivered therapy protocol(s), hours
of therapy delivery or the like. Patient related data, such as that
received from the sensor 86 signal may be stored in memory 82 for
retrieval by a user.
[0037] Therapy delivery circuit 84 may include a charging circuit
92, an output circuit 94, and a switching circuit 96. Charging
circuit 92 may include one or more holding capacitors that are
charged using a multiple of the battery voltage of power source 90,
for example. The holding capacitors are switchably connected to
output circuit 94, which may include one or more output capacitors
that are coupled to a selected bipolar electrode pair via switching
circuit 96. The holding capacitor(s) are charged to a programmed
pacing pulse voltage amplitude by charging circuit 92 and
discharged across the output capacitor for a programmed pulse
width. Charging circuit 92 may include capacitor charge pumps or an
amplifier for the charge source to enable rapid recharging of
holding capacitors included in charging circuit 92. Therapy
delivery circuit 84 responds to control signals from control
circuit 80 for generating and delivering trains of pulses to
produce sustained tetanic contraction of the GG and/or GH muscles
or portions thereof to move the tongue forward and avoid upper
airway obstruction.
[0038] Output circuit 94 may be selectively coupled to bipolar
pairs of electrodes 30a-30d via switching circuit 96. Switching
circuit 96 may include one or more switches activated by timing
signals received from control circuit 80. Electrodes 30a-30d may be
selectively coupled to output circuit 94 in a time-varying manner
to deliver stimulation to different portions of the protrusor
muscles at different time to avoid fatigue, without requiring
stimulation to be withheld completely. Switching circuit 96 may
include a switch array, switch matrix, multiplexer, or any other
type of switching device(s) suitable to selectively couple therapy
delivery circuit 84 to bipolar electrode pairs selected from
electrodes 30. Bipolar electrode pairs may be selected one at a
time or may be selected two or more at time to allow overlapping
stimulation of two or more different portions of the protrusor
muscles. Overlapping stimulation times of two portions of the
protrusor muscles, for example left and right or proximal and
distal may maintain a forward position of the tongue and allow a
ramping up and ramping down of the electrical stimulation being
delivered to two different portions of the protrusor muscles.
[0039] Telemetry circuit 88 is optional but may be included to
enable bidirectional communication with an external programmer 50.
A user, such as the patient 8, may manually adjust therapy control
parameter settings, e.g., as described in Medtronic's Patient
Programmer Model 37642, incorporated by reference in its entirety.
The patient may make limited programming changes such as small
changes in stimulation pulse amplitude and pulse width. The patient
may turn the therapy on and off or set timers to turn the therapy
on or off using external programmer 50 in wireless telemetric
communication with telemetry circuit 88.
[0040] In other examples, a user, such as a clinician, may interact
with a user interface of an external programmer 50 to program pulse
generator 12 according to a desired OSA therapy protocol. For
example, a Physician Programmer Model 8840 available from
Medtronic, Inc., Minneapolis, Minn., may be used by the physician
to program pulse generator 12 for delivering electrical
stimulation.
[0041] Programming of pulse generator 12 may refer generally to the
generation and transfer of commands, programs, or other information
to control the operation of pulse generator 12. For example,
external programmer 50 may transmit programs, parameter
adjustments, program selections, group selections, or other
information to control the operation of pulse generator 12, e.g.,
by wireless telemetry. As one example, external programmer 50 may
transmit parameter adjustments to support therapy changes. As
another example, a user may select programs or program groups. A
program may be characterized by an electrode combination, electrode
polarities, voltage or current amplitude, pulse width, pulse rate,
therapy duration, and/or pattern of electrode selection for
delivering patterns of alternating portions of the protrusor
muscles that are being stimulated. A group may be characterized by
multiple programs that are delivered simultaneously or on an
interleaved or rotating basis. These programs may adjust output
parameters or turn the therapy on or off at different time
intervals.
[0042] External programmer 50 may present patient related and/or
device related data retrieved from memory 82 via telemetry circuit
88. Additionally or alternatively, external programmer 50 may
present sleep sound or motion data stored in memory 82 as
determined from signals from sensor 86. Further, the time periods
in which the patient is lying down can be acquired based on patient
posture detection using sensor 86 and a history of such data can be
stored into memory 82 and retrieved and displayed by external
programmer 50.
[0043] FIG. 3 depicts a single intramuscular lead 20 inserted into
the tongue 40 of a patient. Lead 20 may include two or more
electrodes, and in the example shown lead 20 includes four
electrodes 30a, 30b, 30c, and 30d (collectively referred to as
"electrodes 30") spaced apart longitudinally along lead body 22.
Lead body 22 is a flexible lead body which may define one or more
lumens within which insulated electrical conductors extend to a
respective electrode 30a-30d. The distal most electrode 30a may be
adjacent or proximate to lead distal end 26. Each of electrodes
30b, 30c and 30d are spaced proximally from the respective adjacent
electrode 30a, 30b and 30c by a respective interelectrode distance
34, 35 and 36.
[0044] Each electrode 30a-30d is shown have equivalent electrode
lengths 31. In other examples, however, electrodes 30a-30d may have
electrode lengths 31 that are different from each other in order to
optimize placement of the electrodes 30 or the resulting electrical
field of stimulation relative to targeted stimulation sites
corresponding to left and right portions of the HGN or branches
thereof and/or motor points of the GG and GH muscles. The
interelectrode spacings between electrodes 30a, 30b, 30c, and 30d
are shown to be approximately equal in FIG. 3, however they may
also be different from each other in order to optimize placement of
electrodes 30 relative to the targeted stimulation sites or the
resulting electrical field of stimulation relative to targeted
stimulation sites corresponding to left and right hypoglossal
nerves or branches of hypoglossal nerves and/or motor points of
protrusor muscles 42a, 42, or 46.
[0045] In some examples, electrodes 30a and 30b form an anode and
cathode pair for delivering bipolar stimulation in one portion of
the protrusor muscles, e.g., either the left or right GG and/or GH
muscles or either a proximal or distal portion of the GG and/or GH
muscles. Electrodes 30c and 30d may form a second anode and cathode
pair for delivering bipolar stimulation in a different portion of
the protrusor muscles (e.g., the other of the left or right
portions or the other of the proximal or distal portions).
Accordingly, the interelectrode spacing 35 between the two bipolar
pairs 30a-30b and 30c-30d may be different than the interelectrode
spacing 34 and 36 between the anode and cathode within each bipolar
pair 30a-30b and 30c-30d.
[0046] In one example, the total distance encompassed by electrodes
30a-30d along the lead body 22 may be about 20 millimeter, 25
millimeters, or 30 millimeters as examples. In one example, the
total distance is between 20 and 22 millimeters. The interelectrode
spacings between a proximal electrode pair 30c-30d and a distal
electrode pair 30a-30b, respectively, may be between 2 and 6 mm,
including all integer values therebetween. The interelectrode
spacing separating the distal and proximal pairs 30a-30b and
30c-30d may be the same or different from each other and the
spacing between individual electrodes of any such pair.
[0047] In the example shown, each of electrodes 30a-30d is shown as
a circumferential ring electrode which may be uniform in diameter
with lead body 22. In other examples, electrodes 30 may include
other types of electrodes such as a tip electrode, a helical
electrode, a coil electrode, a segmented electrode, a button
electrode as examples. For instance, the distal most electrode 30a
may be provided as a tip electrode at the lead distal end 26 with
the remaining three electrodes 30b, 30c and 30d being ring
electrodes. When electrode 30a is positioned at the distal end 26,
electrode 30a may be a helical electrode configured to screw into
the muscle tissue at the implant site to additionally serve as a
fixation member for anchoring the lead 20 at the targeted therapy
delivery site. In other examples, one or more of electrodes 30a-d
may be a hook electrode or barbed electrode to provide active
fixation of the lead 20 at the therapy delivery site.
[0048] Lead 20 may include one or more fixation member 32 for
minimizing the likelihood of lead migration. In the example shown,
fixation member 32 includes multiple sets of tines which engage the
surrounding tissue when lead 20 is positioned at the target therapy
delivery site. The tines of fixation member 32 may extend radially
and proximally at an angle relative to the longitudinal axis of
lead body 22 to prevent or reduce retraction of lead body 22 in the
proximal direction. Tines of fixation member 32 may be collapsible
against lead body 22 when lead 20 is held within the confines of a
lead delivery tool, e.g., a needle or introducer, used to deploy
lead 20 at the target implant site. Upon removal of the lead
delivery tool, the tines of fixation member 32 may spread to a
normally extended position to engage with surrounding tissue and
resist proximal and lateral migration of lead body 22. In other
examples, fixation member 32 may include one or more hooks, barbs,
helices, or other fixation mechanisms extending from one or more
longitudinal locations along lead body 22 and/or lead distal end
26. Fixation member 32 may partially or wholly engage the GG, GH
muscles and/or other muscles below the tongue, and/or other soft
tissues of the neck, e.g., fat and connective tissue, when proximal
end of lead body 20 is tunneled to an implant pocket of pulse
generator 12. In other examples, fixation member 32 may include one
or more fixation mechanisms located at other locations than the
location shown in FIG. 3, including at or proximate to distal end
26, between electrodes 30, or otherwise more distally or more
proximally than the location shown. The implant pocket of pulse
generator 12 may be along the patient's neck 8 (see FIG. 1) in the
chest, or in another location as deemed appropriate by the surgeon
performing the implantation. Accordingly the length of the
elongated lead body 22 from distal end 26 to the lead proximal end
24 (FIG. 1) may be selected to extend from the target therapy
delivery site in the protrusor muscles to a location along the
patient's neck where the pulse generator 12 is implanted. This
length may be up to 10 cm or up to 20 cm as examples but may
generally be 25 cm or less, though longer or shorter lead body
lengths may be used depending on the anatomy and size of the
individual patient.
[0049] FIG. 2 is a conceptual diagram 120 of the lead 20 deployed
for delivering OSA therapy according to another example. In this
example, lead 20 carrying electrodes 30 is advanced approximately
along or parallel to midline 102 of tongue 40. In the example
shown, lead body 22 is shown approximately centered along midline
102, however in other examples lead body 22 may be laterally offset
from midline 102 in the left or right directions but is generally
medial to both of the left HGN 104L and the right HGN 104R. The
distal end 26 of lead 20 may be inserted inferiorly to the body of
tongue 40, e.g., at a percutaneous insertion point along the
submandibular triangle, in the musculature below the floor of the
oral cavity. The distal end 26 is advanced to position electrodes
30 medially to the left and right HGNs 104L and 104R, e.g.,
approximately midway between the hyoid bone the mental protuberance
(chin). An electrical field produced by stimulation pulses
delivered between any bipolar pair of electrodes selected from
electrodes 30 may encompass a portion of both the left target
region 106L and the right target region 106R to produce bilateral
stimulation of the HGNs 104L and 104R and therefore bilateral
recruitment of the protrusor muscles. Bilateral recruitment of the
protrusor muscles may provide greater airway opening than
unilateral stimulation that is generally performed using a nerve
cuff electrode along the HGN. For example, electrical stimulation
pulses delivered using electrodes 30a and 30b may produce
electrical field 122 (shown conceptually) encompassing a portion of
both of the left and right target regions 106L and 106R. Electrical
stimulation pulses delivered using electrodes 30c and 30d may
produce electrical field 124 (shown conceptually) encompassing a
portion of both of the left and right target regions 106L and 106R.
The portions of the left and right target regions 106L and 106R
encompassed by electrical field 122 are posterior portions relative
the portions of the left and right target regions 106L and 106R
encompassed by electrical field 124.
[0050] In some examples, electrical stimulation is delivered by
pulse generator 12 by sequentially selecting different electrode
pairs from among the available electrodes 30 to sequentially
recruit different bilateral anterior and bilateral posterior
portions of the HGNs 104L and 104R. This electrode selection may
result in recruitment of different anterior and posterior portions
of the protrusor muscles. The sequential selection of different
electrode pairs may be overlapping or non-overlapping. The
electrical stimulation is delivered throughout an extended time
period encompassing multiple respiratory cycles independent of the
timing of respiratory cycles to maintain a protruded state of
tongue 40 from the beginning of the time period to the end of the
time period. The electrodes 30 may be selected in bipolar pairs
comprising the most distal pair 30a and 30b, the outermost pair 30a
and 30d, the innermost pair 30b and 30c, the most proximal pair 30c
and 30d or alternating electrodes along lead body 22, e.g., 30a and
30c or 30b and 30d. Sequential selection of two or more different
electrode pairs allows for sequential recruitment of different
portions of the protrusor muscles to reduce the likelihood of
fatigue.
[0051] In some examples, electrical stimulation delivered using an
electrode pair, e.g., 30a and 30b, that is relatively more distal
along distal lead portion 28 and implanted relatively anteriorly
along tongue 40 may recruit a greater portion of anterior muscle
fibers, e.g., within the GG muscle. Electrical stimulation
delivered using an electrode pair, e.g., 30c and 30d, that is
relatively more proximal along distal lead portion 28 and implanted
relatively posteriorly along tongue 40 may recruit a greater
portion of posterior muscle fibers, e.g., within the GH muscle.
Sequential selection of electrodes 30 for delivering electrical
stimulation pulses allows sequential recruitment in overlapping or
non-overlapping patterns of anterior and posterior portions of the
protrusor muscles to sustain the tongue in a protruded state
throughout the extended time period while reducing or avoiding
muscle fatigue.
[0052] FIG. 4 is a conceptual diagram of the distal portion of a
dual lead system for delivering OSA therapy. In this example, one
lead 20 is advanced anteriorly approximately parallel to midline
102 and offset, e.g. by 5-8 millimeters to the left of midline 102,
to position distal portion 28 and electrodes 30 in or adjacent to
the left target region 106L. A second lead 220 is advanced
anteriorly approximately parallel to midline 102 but offset
laterally to the right of midline 102 to position distal portion
228 and electrodes 230 in or adjacent the right target region 106R.
Lead 20 may be inserted from a left lateral or posterior approach
of the body of tongue 40, and lead 230 may be inserted from a right
lateral or posterior approach of the body of tongue 40. In other
examples, both leads 20 and 220 may be inserted from only a left or
only a right approach with one lead traversing midline 102 to
position the electrodes 30 or 230 along the opposite side of
midline 102 from the approaching side. Lead 20 and/or lead 220 may
be advanced at an oblique angle relative to midline 102 but may not
cross midline 102. In other examples, one or both leads 20 and 220
may approach and cross midline 102 at an oblique angle such that
one or both of distal portions 28 and 228 extend in or adjacent to
both the right and left target regions 106L and 106R, similar to
the orientation shown in FIG. 6.
[0053] In the example shown, relatively more localized control of
the recruitment of left, right, anterior and posterior portions of
the protrusor muscles may be achieve by selecting different
electrode pairs from among the electrodes 30a through 30d and 230a
through 230d. For example, any combination of electrodes 30a
through 30d may be selected for delivering electrical stimulation
pulses to the left portions of the protrusor muscles. More distal
electrodes 30a and 30b may be selected for stimulation of more
anterior portions of the left protrusor muscles (corresponding to
electrical field 144) and more proximal electrodes 30c and 30d may
be selected for stimulation of more posterior portions of the left
protrusor muscles (corresponding to electrical field 142). Any
combination of electrodes 230a through 230d may be selected for
delivering electrical stimulation pulses to the right portions of
the protrusor muscles. More distal electrodes 230a and 230b may be
selected for stimulation of more anterior portions of the right
protrusor muscles (corresponding to electrical field 154) and more
proximal electrodes 230c and 230d may be selected for stimulation
of more posterior portions of the right protrusor muscles
(corresponding to electrical field 152).
[0054] Switching circuit 96 may be configured to select electrode
pairs that include one electrode on one of leads 20 or 220 and
another electrode on the other lead 20 or 220 to produce an
electrical field (not shown) that encompasses portions of both the
left target region 106L and the right target region 106R
simultaneously for bilateral stimulation. Any combination of the
available electrodes 30a through 30d and electrodes 230a through
230d may be selected as two or more bipolar pairs, which are
selected in a repeated, sequential pattern to sequentially recruit
different portions of the two target regions 106L and 106R. The
sequential selection of electrode pairs may be overlapping or
non-overlapping, but electrical stimulation pulses are delivered
without interruption at one or more selected frequencies throughout
an extended time period to maintain tongue 40 in a protruded state
from the beginning of the time period to the end of the time
period, encompassing multiple respiratory cycles.
[0055] In the example of FIG. 4 including two leads, two pairs of
electrodes may be selected simultaneously and sequentially with one
or more other pairs of electrodes. For example, electrodes 30a and
30b may be selected as one bipolar pair and electrodes 230c and
230d may be selected as a second bipolar pair for simultaneous
stimulation of the left, anterior portion of the target region 106L
and the right posterior portion of the target region 106R. The
electrodes 30c and 30d may be selected as the next bipolar pair
from lead 20, simultaneously with electrodes 230a and 230b selected
as the next bipolar pair from lead 220. In this way, electrical
stimulation may be delivered bilaterally, alternating between
posterior and anterior regions on each side. The anterior left (30a
and 30b) and posterior right (230c and 230d) bipolar pairs may be
selected first, and the posterior left (30c and 30d) and anterior
right (230a and 230b) bipolar pairs may be selected second in a
repeated, alternating fashion to maintain tongue 40 in a protruded
state continuously during an extended time period encompassing
multiple respiratory cycles. In other examples, both of the
anterior pairs (30a-30b and 230a-230b) may be selected
simultaneously first, and both the posterior pairs (30c-30d and
230c-230d) may be selected simultaneously second, sequentially
following the anterior pairs. In this way, continuous bilateral
stimulation may be achieved while sequentially alternating between
posterior and anterior portions to avoid or reduce fatigue. In
contrast to other OSA therapy systems that rely on a sensor for
sensing the inspiratory phase of respiration to coordinate the
therapy with the inspiratory phase, the intramuscular electrodes 30
positioned to stimulate different portions of the protrusor muscles
do not require synchronization to the respiratory cycle.
Alternation of stimulation locations within the protrusor muscles
allows different portions of the muscles to rest while other
portions are activated to avoid collapse of the tongue against the
upper airway while also avoiding muscle fatigue.
[0056] It is to be understood that more or fewer than the four
electrodes shown in the examples presented herein may be included
along the distal portion of a lead used in conjunction with the OSA
therapy techniques disclosed herein. A lead carrying multiple
electrodes for delivering OSA therapy may include 2, 3, 5, 6 or
other selected number of electrodes. When the lead includes only
two electrodes, a second lead having at least one electrode may be
included to provide at least two different bipolar electrode pairs
for sequential stimulation of different portions of the right
and/or left medial HGNs. Furthermore, while the selected electrode
pairs are generally referred to herein as "bipolar pair" including
one cathode and one return anode, it is recognized that three or
more electrodes may be selected at a time to provide desired
electrical field or stimulation vector for recruiting a desired
portion of the protrusor muscles. Accordingly, the cathode of a
bipolar "pair" may include one or more electrodes selected
simultaneously from the available electrodes and/or the anode of
the bipolar "pair" may include one or more electrodes selected
simultaneously from the available electrodes.
[0057] FIG. 5 timing diagram illustrating a method performed by
pulse generator 12 for delivering selective stimulation to the
protrusor muscles for promoting upper airway patency during sleep
according to one example. Electrical stimulation is delivered over
a therapy time period 401 having a starting time 403 and an ending
time (not shown). Electrical stimulation pulses that are delivered
when pulse generator sequentially selects a first bipolar electrode
pair 402 and a second bipolar electrode pair 412 in an alternating,
repeating manner are shown. The first and second bipolar electrode
pairs 402 and 412 may correspond to any two different electrode
pairs described in the examples above in conjunction with FIGS.
3-4.
[0058] A first train of electrical pulses 406 is shown starting at
the onset 403 or therapy time period 401. The first train of
electrical pulses 406 is delivered using bipolar electrode pair 402
for a duty cycle time interval 404. The first train of electrical
pulses 406 has a pulse amplitude 405 and pulse frequency, e.g., 20
to 50 Hz, defined by the interpulse intervals 407. The first train
of electrical pulses 406, also referred to as "pulse train" 406,
may have a ramp on portion 408 during which the pulse amplitude is
gradually increased from a starting voltage amplitude up to pulse
voltage amplitude 405. In other examples, the pulse width may be
gradually increased. In this way the delivered pulse energy is
gradually increased to promote a gentle transition from the
relaxed, non-stimulated state to the protruded state of the
tongue.
[0059] The train of electrical pulses 406 may include a ramp off
portion 410 during which the pulse amplitude (and/or pulse width)
is decremented from the pulse voltage amplitude 405 to an ending
amplitude at the expiration of the duty cycle time interval 404. In
other examples, pulse train 406 may include a ramp on portion 408
and no ramp off portion 410. In this case, the last pulse of pulse
train 406 delivered at the expiration of duty cycle time interval
404 may be delivered at the full pulse voltage amplitude 405. Upon
expiration of the duty cycle time interval 404, electrical
stimulation delivery via bipolar electrode pair 402 is
terminated.
[0060] In the example shown, a second electrode pair 412 is
selected when duty cycle time interval 404 is expiring. The second
electrode pair 412 may be selected such that delivery of electrical
stimulation pulse train 416 starts a ramp on portion 418 that is
simultaneous with the ramp off portion 410 of train 406. In other
examples, the ramp on portion 418 of pulse train 416 may start at
the expiration of the first duty cycle time interval 404. When
pulse train 406 does not include a ramp off portion 410, the pulse
train 416 may be started such that the ramp on portion 418 ends
just before, just after or coincidentally with the expiration of
duty cycle time interval 404. The second pulse train 416 has a
duration of duty cycle time interval 414 and may end with an
optional ramp off portion 420, which may overlap with the ramp on
portion of the next pulse train delivered using the first electrode
pair 402.
[0061] In this example, pulse trains 406 and 416 are shown to be
equivalent in amplitude 405 and 415, pulse width, pulse frequency
(and inter pulse interval 407), and duty cycle time interval 404
and 414. It is contemplated, however, that each of the stimulation
control parameters used to control delivery of the sequential pulse
trains 406 and 416 may be separately controlled and set to
different values as needed to achieve a desired sustained
protrusion of tongue 40 while avoiding or minimizing fatigue.
[0062] The sequential pulse trains 406 and 416 are delivered using
two different electrode pairs 402 and 412 such that different
portions of the protrusor muscles are recruited by the pulse trains
406 and 416 allowing one portion to rest while the other is being
stimulated. However, pulse trains 404 and 406 occur in a sequential
overlapping or non-overlapping manner such that electrical pulses
are delivered at one or more selected frequencies for the entire
duration of the therapy time period 401 to sustain the tongue in a
protruded state throughout time period 401. It is to be understood
that the relative down and/or forward position of the protruded
tongue may shift or change as different electrode pairs are
selected but the tongue remains in a protruded state throughout
therapy time period 401.
[0063] At times, the pulse trains 404 and 406 may be overlapping to
simultaneously recruit the left and right GG and/or GH muscles to
create a relatively greater force (compared to recruitment of a
single side) to pull the tongue forward to open an obstructed upper
airway. In some cases, the overlapping pulse trains 404 and 406 may
cause temporary fatigue of the protrusor muscles along the left or
right side but the temporary fatigue may improve the therapy
effectiveness to ensure an open upper airway during an apneic
episode. Recovery from fatigue will occur between duty cycles and
at the end of an apneic episode. Duty cycle lengths may vary
between patients depending on the fatigue properties of the
individual patient. Control circuit 80 may control the duty cycle
on time in a manner that minimizes or avoids fatigue in a closed
loop system using a signal from sensor 86, e.g., a motion sensor
signal and or electromyography (EMG) signal correlated protrusor
muscle contraction force and subsequent fatigue.
[0064] FIG. 6 is a timing diagram 500 of a method for delivering
OSA therapy by pulse generator 12 according to another example. In
this example, a therapy delivery time period 501 is started at 503
with a ramp on interval 506 delivered using a first bipolar
electrode pair 502. The ramp on interval 506 is followed by a duty
cycle time interval 504. Upon expiration of the duty cycle time
interval 504, a second bipolar electrode pair 512 is selected for
delivering electrical stimulation pulses for a second duty cycle
time interval 514. A third duty cycle time interval 524 starts upon
the expiration of the second duty cycle time interval 514, and
stimulation pulses are delivered by selecting a third bipolar
electrode pair 522 different than the first two pairs 502 and 512.
A fourth bipolar pair 532 is selected upon expiration of the third
duty cycle time interval 524 and used to deliver stimulation pulses
over the fourth duty cycle time interval 534. Upon expiration of
the fourth duty cycle time interval 534, the sequence is repeated
beginning with duty cycle time interval 504 again.
[0065] In this example, four different bipolar pairs are selected
in sequence. The four different bipolar electrode pairs may differ
by at least one electrode and/or the polarity of another bipolar
electrode pair. For example, when a single quadripolar lead 20 is
used, the four bipolar pairs may include 30a-30b, 30b-30c, 30c-30d
and 30a-30d. The portions of the protrusor muscles recruited by the
four different pairs may not be mutually exclusive since the
electrical fields of the four different pairs may stimulate some of
the same nerve fibers. Four different portions of the protrusor
muscles may be recruited, which may include overlapping portions.
The relatively long recovery periods 540, 542, 544 and 546 between
respective duty cycle time intervals allows each different portion
of the protrusor muscles to recover before the next duty cycle.
When recruited muscle portions overlap between selected electrode
pairs, the bipolar electrode pairs may be selected in a sequence
that avoids stimulating the overlapping recruited muscle portions
consecutively. All recruited muscle portions are allowed to recover
during at least a portion of each respective recovery period 540,
54, 544 and/or 546. For example, if the bipolar electrode pair 502
and the bipolar electrode pair 522 recruit overlapping portions of
the protrusor muscles, the recruited portions may still recover
during the second duty cycle time interval 514 and during the
fourth duty cycle time interval 534.
[0066] The duration of each duty cycle time interval, 504, 514, 524
and 534, may be the same or different from each other, resulting in
the same or different overall duty cycles. For example, when four
bipolar electrode pairs are sequentially selected, stimulation
delivery for each individual pair may be a 25% duty cycle. In other
examples, a combination of different duty cycles, e.g., 30%, 10%,
40% and 20%, could be selected in order to promote sustained
protrusion of the tongue with adequate airway opening while
minimizing or avoiding fatigue. The selection of duty cycle may
depend on the particular muscles or muscle portions being recruited
and the associated response (position) of the tongue to the
stimulation for a given electrode pair selection.
[0067] The stimulation control parameters used during each of the
duty cycle time intervals 504, 514, 524, and 534 for delivering
electrical pulses using each of the different bipolar electrode
pairs 502, 512, 522 and 532 may be the same or different. As shown,
a different pulse voltage amplitude and a different interpulse
interval and resulting pulse train frequency may be used. The pulse
amplitude, pulse width, pulse frequency, pulse shape or other pulse
control parameters may be controlled according to settings selected
for each bipolar electrode pair.
[0068] In the example shown, one ramp on portion 506 of the
stimulation protocol is shown at the onset of the therapy delivery
time period 501. Once the stimulation is ramped up to position the
tongue in a protruded position, no other subsequent duty cycle time
intervals 504 (other than the first one), 514, 524 and 534 may
include or be proceeded by a ramp on portion. In other examples, a
ramp on portion may precede each duty cycle time interval (or be
included in the duty cycle time interval as shown in FIG. 5) and
may overlap with the preceding duty cycle time interval. No ramp
off portions are shown in the example of FIG. 6. In other examples,
ramp off portions may follow or be included in each duty cycle time
interval 504, 514, 524 and 534 and may overlap with the onset of
the next duty cycle time interval as shown in FIG. 5. In some
examples, only the last duty cycle time interval (not shown in FIG.
6) may include or be immediately followed by a ramp off portion to
gently allow the tongue to return to a relaxed position at the end
of the therapy delivery time period 501.
[0069] Following implantation as depicted in FIGS. 3 and 4 and
calibration by the surgeon or other caregiver, the INS 10 is ready
for use. In accordance with one aspect of the disclosure, the INS
system 10 is manually switched on by the patient as part of their
routine prior to sleeping. This may be a function of the external
programmer 50, or another similar device that can communicate with
the pulse generator 12 via the telemetry circuit 88. A delay period
may be programmed into the software or firmware employed by the
control circuit 80. The delay period allows the patient a period to
fall asleep before therapy is begun. The period may be established
for the patient based on a variety of factors, including an average
time to sleep observed during, for example, a sleep study and may
be adjusted by the patient via the external programmer 50. Without
the delay period, the patient would immediately begin to experience
the effects of stimulating the protrusor muscles, which though not
dangerous or painful, can be observed and may be considered
annoying to experience while awake.
[0070] As will be appreciated, manual switching as described above,
is not always a desirable feature in an implantable device
associated with sleeping. In a further aspect of the disclosure,
OSA therapy may be started and stopped at scheduled times of day.
Control circuit 80 may include a clock for scheduling the time that
OSA therapy is started and stopped by therapy delivery circuit 84.
Many patients, however, are not as rigorous regarding their
schedules as would be desired to make the scheduling most
effective. Further, the patient may find themselves at a social
gathering or other affair at a time where they are normally
scheduled for sleeping. Additionally, or alternatively, the patient
may find themselves taking an unscheduled nap in a motor vehicle,
plane, or train, and not have an opportunity to initiate or
schedule therapy. Since OSA is often co-morbid with heart related
diseases any instances of experiencing OSA can have complicating
factors affecting the patient's heart. Thus, sensing of sleeping
conditions and initiation of therapy are desirable. One aspect of
the disclosure is directed to a mechanism of initiating therapy
based on a detected state of the tone of the protrusor muscles.
[0071] In accordance with the disclosure, and as noted above, the
electrodes 30 either alone or in combination with the sensor 86 can
be configured to detect electromyography (EMG) signals.
Electromyography is a technique of evaluating and recording the
electrical activity produced by skeletal muscles. An
electromyograph detects the electrical potential generated by
muscle cells when the cells are electrically or neurologically
activated. FIG. 7A, in an upper plot depicts an EMG signal observed
in a genioglossus muscle (GG) 42, in a patient during normal
breathing. The lower plot in FIG. 7A depicts the pharyngeal
pressure during the same period as the EMG signal in the upper
plot. As can be seen in FIG. 7A, during breathing as the pharyngeal
pressure drops, consistent with inhalation, the EMG signal
significantly increases. Those of skill in the art will recognize
that this increase in EMG signal during breathing, signifying
stimulation of the muscles of the tongue such as the genioglossus
muscle (GG) 42, ensures that the airway is not closed or collapsed
easing the ability of the subject to take a breath. That is, at
periods of high EMG signal the protrusor muscles have a contracted
tonal state. At periods where there is a low EMG signal, the
protrusor muscles have a relaxed tonal state.
[0072] FIG. 7B depicts a comparison of observed EMG signals
observed in the protrusor muscles of two sets of subjects. For all
subjects, the EMG signal declines when the subject is in a sleeping
state as compared to a wakeful state. However, significantly for
the instant disclosure, subjects who are experiencing an OSA
episode have a dramatically lower EMG signal. This reduced EMG
signal is evidence of a reduced tonal state of the protrusor
muscles of the subjects experiencing OSA. FIG. 8 depicts similar
data for comparison of the EMG signals during REM, non-REM, quiet
wakefulness, and active wakefulness of subjects. This data confirms
the top line of FIG. 7B that when asleep, the EMG signals are
reduced, and as noted in FIG. 7B, that reduction is more pronounced
and in subjects experiencing an OSA event.
[0073] In accordance with one aspect of the disclosure, when a
stimulation pulse is not being delivered by electrodes 30a-30d, the
electrodes can be employed to detect the electrical potential of
muscles. That is, the electrodes 30a-30d can detect the EMG signals
that are being applied to the protrusor muscles by the patient's
neural system. These signals can be communicated to the control
circuit 80 for monitoring and application of rules in the software
or firmware stored therein. In other examples, dedicated EMG
sensing electrodes may be carried by housing 15 and/or lead body 22
and coupled to sensor 86 for EMG signal monitoring. EMG signal
monitoring by control circuit 80 allows for detection of a low
tonal state of the GG and/or GH muscles. With reference to FIG. 7A
a low tonal state (i.e., low incidence of EMG signals) indicates
both a likelihood of the patient being asleep and a susceptibility
to upper airway collapse. Detection of low tonal state of the
protrusor muscles may either alone or in combination with other
sensor data, e.g., detection of the pose of the patient indicating
that they are in a reclined position or the detection of a heart
rate consistent with sleeping, be used to initiate therapy and
prevent the onset of an OSA event. Thus, the EMG signals may be
used by control circuit 80 to detect a sleep state and/or low tonal
state of the protrusor muscles for use in controlling therapy
delivery circuit 84 for delivering stimulation pulses to cause
protrusion of the patient's tongue. As will be appreciated, in the
detection of the EMG signals a variety of bandpass filtering,
rectification, and normalization may be employed by the control
circuit 80, or intervening hardware to produce a useable signal
providing a clear indication of the state of the protrusor muscles.
An example of such processing of the EMG signal is depicted in FIG.
9.
[0074] EMG monitoring may further be used in monitoring for fatigue
of the stimulated GG and/or GH muscles. If fatigue of the muscles
is detected, control circuit 80 may alter to control the duty cycle
of electrical stimulation pulse trains delivered by therapy
delivery circuit 84 to minimize or avoid fatigue and/or allow
adequate fatigue recovery time between duty cycle on times. In this
manner, Sensor 86 may be configured to produce a signal that is
correlated to protrusor muscle tonal state for use by control
circuit 80 for detecting a low tonal state predictive of upper
airway obstruction, detecting protrusor muscle fatigue, and/or
detecting a protruded state of tongue 40. Therapy delivery circuit
84 may be configured to respond to a detection of the protrusor
muscle tonal state by control circuit 80 by adjusting one or more
control parameters used to control stimulation pulse delivery.
[0075] As noted above, the EMG monitoring may not be the only
signal employed by the pulse generator 12, and particularly the
control circuit 80 in determining the level of wakefulness. As an
example, sensor 86 may include an accelerometer that can provide an
indication of motion of the patient. Further, where the
accelerometer 86 is a three-axis accelerometer, a posture of the
patient may be determined. Additionally, an accelerometer may be
employed to detect snoring sounds and physical movements of the
patient. Still further, a temperature sensor may be employed in
which the diurnal temperature of a patient is measured and stored
in memory as are sleeping temperatures. The sensor 86 may also be
one or more accelerometers employed to detect the heartrate of a
patient. In another example, sensor 86 may be an accelerometer
employed to detect the rate of breathing or the volume of airflow,
into or out of the patient. Volume of airflow may be determined by
placing the accelerometer at a point on a patient's chest and
comparing the travel of the accelerometer to previously observed
lung volume data that has been correlated to the sensor 86 movement
data. Breathing rate can be determined by simply monitoring the
change in direction of the accelerometer.
[0076] Still further, the sensor 86 may be an implantable
pulse-oximeter useable to measure the blood oxygen saturation
levels. In one example the pulse-oximeter is a cuff placed
substantially around a blood vessel and measuring the
blood-oxygenation levels using a light source as is known in the
art. As described herein, the sensor 86 may be one or several of
the various types of sensors described herein.
[0077] The sensor 86 may be an ECG sensor. ECG is a recording of
the electrical activity of the heart over a period of time. While
an ECG typically employs sensors placed on the skin, an effective
ECG can be employed in an implantable device wherein at least two
electrodes separated by a distance (e.g., at least about 35 mm) are
employed to detect electrical changes caused by the cardiac
depolarization and repolarization during each cardiac cycle.
[0078] A further aspect of the disclosure is described in
connection with FIGS. 10 and 11 in which a simplified diagram of an
INS system is depicted, and a method of the systems operation are
described. The system 600 includes an INS device 10, an external
programmer 50, a server 602 in communication with the external
programmer and a remote computer 604 in communication with the
server 602. Prior to implantation of an INS 10, patients typically
undergo a patient assessment (step 702) one or more analyses in
conjunction with their doctor. During this analysis a variety of
self-reported issues may be identified including daytime
sleepiness, interrupted snoring, gasping, co-morbidities, etc. The
data related to these issues may be stored on the server 602 as
part of the patient electronic medical records (EMR) or as part of
a specific OSA treatment and remediation file. The discussions with
the medical provider may lead to an initial diagnosis of OSA. This
initial diagnosis is typically confirmed through the use of one or
more sleep studies of the patient. During the sleep study a wide
variety of physiological data is gathered as well as some
self-reported data. For example, the heart rate, blood oxygen
saturation levels, temperature, an electroencephalogram (EEG),
electrocardiogram (ECG), total sleep, quality of sleep, sleep
efficiency, sleep stages, number of arousals (less than 15 s),
number of awakenings (greater than 15 s), Apnea Hypopnea Index as
well as others. These data may be recorded by remote computer 604,
either directly or via additional hardware, and saved on the remote
server 602 (step 704).
[0079] These collected data from the sleep study, along with the
data collected by the medical provider may be used to generate an
initial set of stimulation parameters (e.g., pulse width,
frequency, amplitude, pairing of electrodes, etc.) for the INS 10
(step 706). This may be in part based on larger population studies
to identify some aspects of more global therapy parameters. The
initial stimulation parameters may be set either at remote computer
604 or directly at external programmer 50, and in either event may
be saved a server 602 (e.g., a cloud computer storage device), for
access by either device. And the external programmer 50 can be
employed to install the initial stimulation parameters in the INS
10 (step 708). Often, the patient is permitted to utilize the INS
10 for a period of time, and a subsequent sleep study may be
performed. From this second sleep study, the initial stimulation
parameters may be altered, or additional surgery may be recommended
to those who do not respond to stimulation therapy. Further sleep
studies may be required periodically to adjust the stimulation
parameter settings in an effort to improve the therapy of the
individual patient.
[0080] In accordance with the present disclosure, the data
collected from the sensor 86 may be combined with various
self-reported data that a user may input via a user interface on
the external programmer 50 and utilized to replace at least the
second sleep study, and possibly the first as well. The external
programmer 50, or another device in communication with the server
602, presents the patient with a user interface. The user interface
may be presented to the user on a periodic basis including daily,
weekly, bi-weekly, or monthly. In accordance, with the daily
embodiment, the user interface may request that the patient input
various self-reporting data. This can include nightly alcohol
intake, smoking, stress, the time the patient went to bed, the
patient's perception of the quality of the last night's sleep,
tiredness, discomfort, pain or soreness of the protrusor muscles
potentially caused by the stimulation, etc. Additionally, data from
other appliances may also be reported. For example, may patients
suffering from OSA also suffer from high blood pressure, and may be
on a regimen of periodically testing their blood pressure. This
blood pressure data may be self-reported via the user interface.
Similarly, if the patient is a diabetic, they may need to test
their blood sugar levels both before and after sleep. These data
too may be self-reported via the user interface. In addition, the
patient may be asked to answer the inquiries of the Eppsworth
Sleepiness Scale (ESS). In one embodiment, the ESS inquiry may be
requested of the patient at a different interval that the other
data. In this way the ESS can be used as one gauge of the
effectiveness of the therapy.
[0081] As noted above, the sensor 86 can provide a variety of data
dependent upon how it is configured. As one example using the EMG
data, a sleep start and end time may be determined. Using one or
more accelerometers and a variety of bandpass filtering position,
activity (arousals vs awakenings), sleep stages, respiration rate,
and heart rate can be collected. This data can be reported to the
control circuit 80 and stored in memory 82 at least temporarily.
The external programmer 50 can be set to automatically interface
with the INS 10 every day, or at another periodic interval. The
external programmer 50 can then download the sensor data via the
telemetry circuit and communicate the sensor data from the INS and
self-reported data entered via the user-interface to the server 602
(step 710).
[0082] The server 602 may include thereon one or more software
applications. One of these applications may review the data
received from the external programmer 50 and assign a value to each
datapoint received. These values can be analyzed, and a sleep score
determined based on the received sensor and self-reported data
(step 712). The sleep score provides an overall assessment of the
patient's sleep that can be assessed by both the patient and the
medical provider. As will be apparent some data points may be more
important to assessing the overall sleep of the patient thus some
form of scaling of the values may be required. The application will
also be able to flag any relevant data significant to a poor sleep
score. For example, if the patient reported several alcoholic
drinks the evening before the data resulting in the poor sleep
score was recorded, this might be a highly relevant factor, and
indicate that the sleep score for that day is not an accurate
indicator of the effectiveness of the current stimulation
parameters.
[0083] Regardless, the sleep score may then be recorded as part of
the patient's sleep record and the score reported to a medical
provider via the remote computer 604 (step 714) . This data may be
viewed in a variety of ways to provide the medical provider an
assessment of the current stimulation parameters. For example, the
medical provider may view the daily results, an average over a
period of time, a graphical representation of the sleep score or a
percentage or rate of change (if any) from the preceding reporting
period. By periodically assessing the effectiveness of the
parameters and comparing the effectiveness to the additional
self-reported data a multi-pronged analysis can be undertaken. In
one example if the patient's data indicates that the therapy is
effective in achieving quality sleep with few incidents of OSA, but
the patient expresses a feeling of soreness or fatigue of the
protrusor muscles, the stimulation parameters may be changed to
increase the frequency of the switching between bi-polar pairs and
to prolong the interval between any set of bi-polar pairs being
stimulated. Alternatively, the amplitude of the signal may be
reduced. Further, following further sampling of the data collected
by the sensor 86 and self-reported by the patient via the user
interface, if the first of these is not effective, the second may
be attempted. In this way, the medical provider is able to proceed
in a stepwise fashion of altering the stimulation parameters, make
adjustments, and observing the results of those adjustments while
considering not just the self-reported data. This collection of
data and reporting of a sleep score (steps 710-714) may be
iterative repeated prior to advancing to the next step. One of
skill in the art will recognize that the remote computer may in
fact be an external programmer 50 configured for physician or
medical care provider's use.
[0084] In a further aspect of the disclosure, the server 602 may
collect or be in communication one or more further servers
receiving similar data from other patients. The entirety of the
collected data may then be analyzed by one or more neural networks
to assess the combined data and to identify patterns within the
data to provide a global assessment of stimulation parameters and
effectiveness of the stimulation pattens when applied across a wide
array of patients. Some of these patients will have similar
comorbidities, and others will not. By further assessment of the
data the neural network can seek out similar groups of patients and
provide refined initial stimulation parameters for the subgroup
based on these similarities (e.g., age, demographics, weight, heart
disease, blood pressure, etc.). The neural network may also be
employed to assess an individual patient to provide individualized
guidance on updating stimulation parameters. In a similar fashion,
the server may include one or more applications employing fuzzy
logic to analyze the data from both an individual and from the
broader community of patients to provide suggestions for updating
the stimulation parameters (step 716). In both the use of neural
networks and fuzzy logic the application on the server 602 may
present the medical provider with the option to reject the
suggested updated stimulation parameters (step 718) or to accept or
modify the suggested updated stimulation parameters (step 720). As
will be appreciated, the medical provider may forgo the use of
either the neural network or fuzzy logic and update or modify the
stimulation parameters. Once the updated stimulation parameters are
accepted/modified by the medical provider the updated stimulation
parameters are communicated to the external programmer 50 (step
722). Once received at the external programmer 50, the patient
again may have the option to accept the updated stimulation
parameters (step 724) or reject the updated stimulation parameters
(step 726). If accepted by the patient the external programmer 50
can update the stimulation parameters on the INS (step 728). If at
step 718 or 726 the updated stimulation parameters are rejected,
the method simply returns to step 710. Similarly, after updating
the stimulation parameters on the INS 10, the process similarly
returns to step 710.
[0085] These updated stimulation parameters may be stored on the
server 602 until the next communication with the remote programmer
50, at which time the improved stimulation parameters may be
downloaded to the external programmer 50. During the next
collection of data from the INS 10, the external programmer 50 may
then download the updated stimulation parameters to the INS 10. In
this way, the stimulation parameters of the INS updated, and the
patient's sleep score improved. As would be expected the user
interface on the external programmer 50 would indicate to the
patient that the new stimulation parameters are ready for
installing on the INS, and it is at this point that steps 726 and
724 may be performed.
[0086] A further aspect of the present disclosure is the presence
of an artificial intelligence (AI) within the external programmer
50. The AI may have a limited mandate for purposes of safety of the
patient to limit the number of successive nights resulting in a
poor sleep score. In one aspect of the disclosure, following the
update of the stimulation parameters and receiving the data from
the following night's sleep, the AI could analyze the data from
sensor 86 and the self-reported data and make an immediate
assessment regarding the sleep score (step 730). If the sleep score
is bad the user interface may present the patient with the ability
to revert to the prior stimulation parameters until they can
interface with their medical provider regarding the prior bad
night's sleep (step 732). Of course, the AI may require more than a
single night's data to identify the issue or have sufficient data
to raise concerns with the patient. Further, the AI may be enabled
to communicate a request for intervention directly to the medical
provider via the server 602 and remote computer 604.
[0087] In this way real actionable feedback on the effectiveness of
stimulation parameters is provided to both the medical provider and
to the patient. A continuum of care and assessment of the patient's
experience with the INS device is enabled so that adverse results
from therapy can be rectified and behavioral modifications can be
suggested to the patient based on their self-reported data.
[0088] It will be appreciated by those of skill in the art that one
or more of the calculations, assessments, and user interfaces
described herein above with respect to the server 602 and the
remote computer 604 may also be performed directly at the external
programmer 50. In some embodiments this may provide for near
instant feedback to the patient regarding a prior night's sleep via
a user interface on the external programmer. In other embodiments,
where the external programmer 50 is of a type typically used by the
physician during an office visit, the capabilities and functions of
the external programmer 50 can be more robust and potentially even
eliminate or at least reduce the use of the server 602 and remote
computer 604. As a further, example, in applications employing an
AI, the AI may be trained to perform all of the assessments and
analyses of the server and offer up the suggestions for
modification of the stimulation parameters to the patient or care
provider. allowing a greater depth of understanding of the therapy,
efficacy, and assessment of possible changes, without necessarily
requiring access to the data stored on the server 602 or the
applications operating thereon. And in yet a further example, the
AI on the external programmer 50 may assess the data received from
the INS 10 and make adjustments to the stimulation parameters
either autonomously or present them to the patient for acceptance.
As will be appreciated, these updates may be bounded to prevent
large changes in the stimulation parameters from occurring without
intervention from a medical provider.
[0089] It should be understood that, depending on the example,
certain acts or events of any of the methods described herein can
be performed in a different sequence, may be added, merged, or left
out altogether (e.g., not all described acts or events are
necessary for the practice of the method). Moreover, in certain
examples, acts or events may be performed concurrently, e.g.,
through multi-threaded processing, interrupt processing, or
multiple processors, rather than sequentially. In addition, while
certain aspects of this disclosure are described as being performed
by a single module or unit for purposes of clarity, it should be
understood that the techniques of this disclosure may be performed
by a combination of units or modules associated with, for example,
a medical device.
[0090] In one or more examples, the functions described may be
implemented in hardware, software, firmware, or any combination
thereof. If implemented in software, the functions may be stored as
one or more instructions or code on a computer-readable medium and
executed by a hardware-based processing unit. Computer-readable
media may include computer-readable storage media, which
corresponds to a tangible medium such as data storage media (e.g.,
RAM, ROM, EEPROM, flash memory, or any other medium that can be
used to store desired program code in the form of instructions or
data structures and that can be accessed by a computer).
[0091] Instructions may be executed by one or more processors, such
as one or more digital signal processors (DSPs), general purpose
microprocessors, application specific integrated circuits (ASICs),
field programmable logic arrays (FPGAs), or other equivalent
integrated or discrete logic circuitry. Accordingly, the term
"processor," as used herein may refer to any of the foregoing
structure or any other structure suitable for implementation of the
techniques described herein. Also, the techniques could be fully
implemented in one or more circuits or logic elements.
[0092] Thus, an implantable medical device system has been
presented in the foregoing description with reference to specific
examples. It is to be understood that various aspects disclosed
herein may be combined in different combinations than the specific
combinations presented in the accompanying drawings. It is
appreciated that various modifications to the referenced examples
may be made without departing from the scope of the disclosure and
the following claims.
* * * * *