U.S. patent application number 15/866164 was filed with the patent office on 2020-01-30 for method and system for applying stimulation in treating sleep disordered breathing.
This patent application is currently assigned to INSPIRE MEDICAL SYSTEMS, INC.. The applicant listed for this patent is INSPIRE MEDICAL SYSTEMS, INC.. Invention is credited to Mark A. Christopherson, Quan Ni, John Rondoni.
Application Number | 20200030609 15/866164 |
Document ID | / |
Family ID | 46682960 |
Filed Date | 2020-01-30 |
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United States Patent
Application |
20200030609 |
Kind Code |
A9 |
Ni; Quan ; et al. |
January 30, 2020 |
METHOD AND SYSTEM FOR APPLYING STIMULATION IN TREATING SLEEP
DISORDERED BREATHING
Abstract
A stimulation protocol determination system includes an input
module and a selector module. The input module is provided to
receive an indication of an upper airway flow limitation via sensed
respiratory effort information. The selection module is provided to
automatically select, based on the indicated upper airway flow
limitation, a stimulation protocol.
Inventors: |
Ni; Quan; (Golden Valley,
MN) ; Christopherson; Mark A.; (Golden Valley,
MN) ; Rondoni; John; (Golden Valley, MN) |
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Applicant: |
Name |
City |
State |
Country |
Type |
INSPIRE MEDICAL SYSTEMS, INC. |
Golden Valley |
MN |
US |
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Assignee: |
INSPIRE MEDICAL SYSTEMS,
INC.
Golden Valley
MN
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Prior
Publication: |
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Document Identifier |
Publication Date |
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US 20190009093 A1 |
January 10, 2019 |
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Family ID: |
46682960 |
Appl. No.: |
15/866164 |
Filed: |
January 9, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14238359 |
Oct 14, 2014 |
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PCT/US12/50615 |
Aug 13, 2012 |
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15866164 |
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61522426 |
Aug 11, 2011 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 5/0402 20130101;
A61B 2562/0247 20130101; A61B 5/053 20130101; A61B 5/08 20130101;
A61B 5/0826 20130101; A61N 1/0556 20130101; A61B 5/085 20130101;
A61N 1/36139 20130101; A61B 5/087 20130101; A61B 5/686 20130101;
A61B 5/4836 20130101; A61N 1/3611 20130101 |
International
Class: |
A61N 1/36 20060101
A61N001/36; A61N 1/05 20060101 A61N001/05; A61B 5/00 20060101
A61B005/00 |
Claims
1. A stimulation protocol determination system comprising: an input
module to receive an indication of an upper airway flow limitation
via sensed respiratory effort information; and a selection module
to automatically select, based on the indicated upper airway flow
limitation, a stimulation protocol including at least one of: a
first protocol to apply stimulation generally synchronous with an
expiratory phase of a respiratory cycle; and a second protocol to
apply stimulation during both of a portion of an inspiratory phase
of the respiratory cycle and a portion of the expiratory phase.
2. The system of claim 1, wherein the indicated upper airway flow
limitation corresponds to at least a partial obstruction of the
upper airway associated with sleep apneas.
3. The system of claim 1, wherein the first protocol is
automatically selected when the indicated upper airway flow
limitation predominantly coincides with the expiratory phase.
4. The system of claim 1, wherein the second protocol is
automatically selected when the indicated upper airway flow
limitation predominantly coincides with both of a first portion of
the inspiratory phase and a first portion of the expiratory phase
but does not predominantly coincide with a second portion of
inspiratory phase and with a second portion of the expiratory
phase.
5. The system of claim 4, wherein the first portion of the
inspiratory phase includes at least an end portion of the
inspiratory phase and the first portion of the expiratory phase
includes at least a beginning portion of the expiratory phase.
6. The system of claim 5, wherein the first portion of the
inspiratory phase excludes a beginning portion of the inspiratory
phase.
7. The system of claim 5, wherein the second portion of the
expiratory phase excludes an end portion of the expiratory
phase.
8. The system of claim 5, wherein the second protocol includes a
generally continuous stimulation period applied during at least a
portion of at least some respiratory cycles, wherein the generally
continuous stimulation period predominantly coincides with the
first portion of the inspiratory phase and with the first portion
of the expiratory phase, and wherein the generally continuous
stimulation period includes an initial start point located after a
beginning of the inspiratory phase and an initial termination point
located prior to an end of the expiratory phase.
9. The system of claim 8, wherein the second protocol includes the
application of the generally continuous stimulation period for a
set of consecutive respiratory cycles over a first time period and
wherein the input module is configured to: determine if at least
some indications of upper airway flow limitations (exceeding a
dysfunction threshold) are received within the first time period;
maintain or increase a duration of the generally continuous
stimulation period if the input module receives the at least some
indications during the first time period; reduce the duration of
the generally continuous stimulation period if the input module
receives no indications during the first time period.
10. The system of claim 9, wherein the first time period, based on
an apnea-hypopnea index, for which an apnea would likely occur in
the absence of stimulation.
11. The system of claim 9, wherein reducing the duration includes
at least one of: decrementally moving the initial start point
closer to the end portion of the inspiratory phase for the next set
of consecutive respiratory cycles; decrementally moving the initial
termination point closer to the beginning portion of the expiratory
phase for the next set of consecutive respiratory cycles.
12. The system of claim 8, wherein a first portion of the generally
continuous stimulation period coincides with the first portion of
the inspiratory phase and has a duration of at least one of: at
least one-third of an entirety of the inspiratory phase; at least
one-half of the entirety of the inspiratory phase; and at least
two-thirds of the entirety of the inspiratory phase.
13. The system of claim 8, wherein a second portion of the
generally continuous stimulation period coincides with the first
portion of the expiratory phase and has a duration of at least one
of: at least one-third of the entirety of the expiratory phase; at
least one-half of the entirety of the expiratory phase; and at
least two-thirds of the entirety of the expiratory phase.
14. The system of claim 5, wherein the first portion of the
inspiratory phase corresponds to at least a majority of the
inspiratory phase and the first portion of the expiratory phase
corresponds to at least a majority of the expiratory phase.
15. The system of claim 14, wherein the majority of the inspiratory
phase comprises at least two-thirds of the inspiratory phase and
the majority of the expiratory phase comprises at least two-thirds
of the expiratory phase.
16. The system of claim 1, wherein the selection module is
configured to automatically select a third protocol to apply
stimulation generally synchronous with the inspiratory phase when
the flow limitation generally coincides with the inspiratory
phase.
17. The system of claim 1, comprising an implantable pulse
generator; and a nerve cuff electrode electrical couplable to the
pulse generator to apply a respective one of the first and second
stimulation protocols.
18. The system of claim 1, wherein the nerve is the hypoglossal
nerve.
19. The system of claim 16, comprising: a respiration sensor to
provide the sensed respiratory effort information.
20. A non-transitory computer readable medium for storing machine
readable instructions to provide a stimulation protocol
determination module comprising: an input function to receive an
indication of an upper airway flow limitation via sensed
respiratory effort information; and a selection function to
automatically select, based on the indicated upper airway flow
limitation, a stimulation protocol including at least one of: a
first protocol to apply stimulation generally synchronous with an
expiratory phase of a respiratory cycle; and a second protocol to
apply stimulation during a portion of both of an inspiratory phase
of the respiratory cycle and the expiratory phase.
21. A stimulation protocol determination system comprising: a
non-volatile memory for storing, and a processor for executing,
machine readable instructions to provide: an input module to
receive an indication of an upper airway flow limitation via sensed
respiratory effort information; and a selection module to
automatically select, based on the indicated upper airway flow
limitation, a stimulation protocol including at least one of: a
first protocol to apply stimulation generally synchronous with an
expiratory phase of a respiratory cycle; and a second protocol to
apply stimulation during a portion of both of an inspiratory phase
of the respiratory cycle and the expiratory phase.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This Continuation Patent Application claims benefit of U.S.
National Stage application Ser. No. 14/238,359, entitled "Nerve
Stimulation Protocol Determination" filed Oct. 14, 2014,
PCT/US12/50615, entitled "System for Selecting a Stimulation
Protocol Based on Sensed Respiratory Effort" filed Aug. 13, 2012,
and Provisional U.S. Patent Application No. 61/522,426, entitled
"Method and System for Applying Stimulation in Treating Sleep
Disordered Breathing," filed Aug. 11, 2011, all of which are
incorporated herein by reference.
BACKGROUND
[0002] In cases in which sleep disordered breathing is caused by
upper airway obstructions, one form of treatment includes
stimulating one or more nerves that affect upper airway dilation.
In a conventional technique, the stimulation is applied
continuously or synchronized to the respiratory cycle. However, in
some instances, continuous stimulation may not desirable because of
any potential long-term effects of over-stimulating the nerve.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] The accompanying drawings are included to provide a further
understanding of embodiments and are incorporated in and constitute
a part of this specification. The drawings illustrate embodiments
and together with the description serve to explain principles of
embodiments. Other embodiments and many of the intended advantages
of embodiments will be readily appreciated as they become better
understood by reference to the following detailed description. The
elements of the drawings are not necessarily to scale relative to
each other. Like reference numerals designate corresponding similar
parts.
[0004] FIG. 1A is a schematic diagram of an at least partially
implantable stimulation system relative to a patient, according to
an example of the present disclosure.
[0005] FIG. 1B is a block diagram schematically illustrating a
pulse generator, according to one example of the present
disclosure.
[0006] FIG. 1C is flow diagram schematically illustrating a method
of treating an upper airway flow limitation, according to one
example of the present disclosure.
[0007] FIG. 2 is a diagram schematically illustrating respiratory
cycles in one example breathing pattern, according to one example
of the present disclosure.
[0008] FIG. 3 is a diagram schematically illustrating a first
respiratory cycle exhibiting a flow limitation that occurs
predominantly during an inspiratory phase and schematically
illustrating a second respiratory cycle exhibiting mitigation of
the flow limitation in response to a nerve stimulation protocol,
according to one example of the present disclosure.
[0009] FIG. 4 is a diagram schematically illustrating a first
respiratory cycle exhibiting a flow limitation that occurs
predominantly during an expiratory phase and schematically
illustrating a second respiratory cycle exhibiting mitigation of
the flow limitation in response to a nerve stimulation protocol,
according to one example of the present disclosure.
[0010] FIG. 5A is a diagram schematically illustrating a first
respiratory cycle exhibiting a mixed flow limitation that overlaps
a portion of an inspiratory phase and a portion of an expiratory
phase and schematically illustrating a second respiratory cycle
exhibiting mitigation of the flow limitation in response to one
example nerve stimulation protocol, according to one example of the
present disclosure.
[0011] FIG. 5B is a diagram schematically illustrating portions of
a generally continuous stimulation period relative to portions of
the respective inspiratory and expiratory phases of a respiratory
cycle, according to one example of the present disclosure.
[0012] FIG. 6 is a diagram schematically illustrating a first
respiratory cycle exhibiting a mixed flow limitation that overlaps
a portion of an inspiratory phase and a portion of an expiratory
phase and schematically illustrating a second respiratory cycle
exhibiting mitigation of the flow limitation in response to one
example nerve stimulation protocol, according to one example of the
present disclosure.
[0013] FIGS. 7A-7B are a pair of diagrams with each diagram
schematically illustrating a series of respiratory cycles during
which one example nerve stimulation protocol is applied, according
to one example of the present disclosure.
[0014] FIGS. 8-13 are a series of diagrams with each diagram
schematically illustrating a respiratory cycle during which one
example nerve stimulation protocols is applied, according to one
example of the present disclosure.
DETAILED DESCRIPTION
[0015] In the following Detailed Description, reference is made to
the accompanying drawings which form a part hereof, and in which is
shown specific examples of the present disclosure which may be
practiced. In this regard, directional terminology, such as "top,"
"bottom," "front," "back," "leading," "trailing," etc., is used
with reference to the orientation of the Figure(s) being described.
Because components of examples of the present disclosure can be
positioned in a number of different orientations, the directional
terminology is used for purposes of illustration and is in no way
limiting. It is to be understood that other examples may be
utilized and structural or logical changes may be made without
departing from the scope of the present disclosure. The following
detailed description, therefore, is not to be taken in a limiting
sense.
[0016] At least some examples of the present disclosure are
directed to methods of treating obstructive sleep apnea via
applying stimulation in intervals or periods during targeted
portions of the respiratory cycle. By doing so, upper airway
patency is maintained and/or increased while preventing collapse of
the upper airway. At the same time, by using targeted stimulation,
one can limit the overall volume of stimulation applied to a given
nerve or set of nerves.
[0017] FIG. 1A is a schematic diagram of an at least partially
implantable stimulation system, according to an example of the
present disclosure. As illustrated in FIG. 1A, in one example
system 10 an implantable pulse generator (IPG) 35, capable of being
surgically positioned within a pectoral region of a patient 20, and
a stimulation lead 32 electrically coupled with the IPG 35 via a
connector (not shown) positioned within a connection port of the
IPG 35. The lead 32 includes a stimulation electrode portion 45 and
extends from the IPG 35 so that the stimulation electrode portion
45 is positioned in contact with a desired nerve, such as the
hypoglossal nerve 33 of the patient 10, to enable stimulation of
the nerve 33, as described below in detail. An exemplary
implantable stimulation system in which lead 32 may be utilized,
for example, is described in U.S. Pat. No. 6,572,543 to
Christopherson et al., and which is incorporated herein by
reference in its entirety. In one embodiment, the lead 32 further
includes at least one sensor portion 40 (electrically coupled to
the IPG 35 and extending from the IPG 35) positioned in the patient
10 for sensing respiratory effort, such as respiratory
pressure.
[0018] In some embodiments, the sensor portion 40 detects
respiratory effort including respiratory patterns (e.g.,
inspiration, expiration, respiratory pause, etc.) in order to
trigger activation of an electrode portion to stimulate a target
nerve. Accordingly, with this arrangement, the IPG 35 (FIG. 1)
receives sensor waveforms from the respiratory sensor portion 40,
thereby enabling the IPG 35 to deliver electrical stimulation
synchronously with inspiration (or synchronized relative to another
aspect of the respiratory cycle) according to a therapeutic
treatment regimen in accordance with examples of the present
disclosure. It is also understood that the respiratory sensor
portion 40 is powered by the IPG 35 and the IPG 35 also contains
internal circuitry to accept and process the impedance signal from
the stimulation lead 32.
[0019] In some embodiments, the sensor portion 60 is a pressure
sensor. In one example, the pressure sensor in this embodiment
detects pressure in the thorax of the patient. In other examples,
the sensed pressure could be a combination of thoracic pressure and
cardiac pressure (e.g., blood flow). With this configuration, the
controller is configured to analyze this pressure sensing
information to detect the respiratory patterns of the patient.
[0020] In some other embodiments, the respiratory sensor portion 40
comprises a bio-impedance sensor or pair of bio-impedance sensors
and can be located in regions other than the pectoral region. In
one aspect, such an impedance sensor is configured to sense a
bio-impedance signal or pattern whereby the control unit evaluates
respiratory patterns within the bio-impedance signal. For
bio-impedance sensing, in one embodiment, electric current will be
injected through an electrode portion within the body and an
electrically conductive portion of a case of the IPG 35 (FIG. 3A)
with the voltage being sensed between two spaced apart stimulation
electrode portions (or also between one of the stimulation
electrode portions and the electrically conductive portion of the
case of IPG 35) to compute the impedance.
[0021] In some embodiments, system 10 also comprises additional
sensors to further obtain physiologic data associated with
respiratory functions. For example, system 10 may include various
sensors (e.g., sensors 47, 48, 49 in FIG. 1) distributed about the
chest area for measuring a trans-thoracic bio-impedance signal, an
electrocardiogram (ECG) signal, or other respiratory-associated
signals.
[0022] In some embodiments, the sensing and stimulation system for
treating obstructive sleep apnea is a totally implantable system
which provides therapeutic solutions for patients diagnosed with
obstructive sleep apnea. In other embodiments, one or more
components of the system are not implanted in a body of the
patient. A few non-limiting examples of such non-implanted
components include external sensors (respiration, impedance, etc.),
an external processing unit, or an external power source. Of
course, it is further understood that the implanted portion(s) of
the system provides a communication pathway to enable transmission
of data and/or controls signals both to and from the implanted
portions of the system relative to the external portions of the
system. The communication pathway includes a radiofrequency (RF)
telemetry link or other wireless communication protocols.
[0023] Whether partially implantable or totally implantable, the
system is designed to stimulate the hypoglossal nerve during some
portion of the repeating respiratory cycle to thereby prevent
obstructions or occlusions in the upper airway during sleep. In one
embodiment, the implantable system comprises an implantable pulse
generator (IPG), a peripheral nerve cuff stimulation lead, and a
pressure sensing lead.
[0024] FIG. 1B is a block diagram schematically illustrating an
implantable pulse generator (IPG) 60, according to one example of
the present disclosure. In one embodiment, IPG 60 generally
includes at least substantially the same features and attributes as
IPG 35 of FIG. 1A. As illustrated in FIG. 1B, in one example,
implantable pulse generator 60 includes controller 62, memory 64,
sensing module 66, stimulation module 68, patient management module
70, and a therapy manager 72.
[0025] Via an array of parameters, the sensing module 66 receives
and tracks signals from various physiologic sensors (such as a
pressure sensor, blood oxygenation sensor, acoustic sensor,
electrocardiogram (ECG) sensor, or impedance sensor) in order to
determine a respiratory state of a patient, whether or not the
patient is asleep or awake, and other respiratory-associated
indicators, etc. Such respiratory detection may be received from
either a single sensor or any multiple of sensors, or combination
of various physiologic sensors which may provide a more reliable
and accurate signal. In one example, sensing module 90 receives
signals from sensor portion 40 and/or sensors 47, 48, 49 in FIG.
1A.
[0026] In one example, a controller 62 of IPG 60 comprises one or
more processing units and associated memories configured to
generate control signals directing the operation of IPG 60 and
system 10 (FIG. 1A). In particular, in response to or based upon
commands received via an input and/or machine readable instructions
(including software) contained in the memory 64 associated with the
controller 62 in response to physiologic data gathered via the
sensors, controller 62 generates control signals directing
operation of pulse generator 60 to selectively control stimulation
of a target nerve, such as the hypoglossal nerve, to restore airway
patency and thereby reduce or eliminate apnea events. In one
example, controller 62 is embodied in a general purpose
computer.
[0027] For purposes of this application, in reference to the
controller 62, the term "processor" shall mean a presently
developed or future developed processor (or processing resources)
that executes sequences of machine readable instructions (such as
but not limited to software) contained in a memory. Execution of
the sequences of machine readable instructions causes the processor
to perform actions, such as operating IPG 60 to provide apply
stimulation to a nerve in the manner described in the examples of
the present disclosure. The machine readable instructions may be
loaded in a random access memory (RAM) for execution by the
processor from their stored location in a read only memory (ROM), a
mass storage device, or some other persistent storage or
non-volatile form of memory, as represented by memory 64. In one
example, memory 64 comprises a computer readable medium providing
non-transitory or non-volatile storage of the machine readable
instructions executable by a process of controller 62. In other
examples, hard wired circuitry may be used in place of or in
combination with machine readable instructions (including software)
to implement the functions described. For example, controller 62
may be embodied as part of at least one application-specific
integrated circuit (ASIC). In at least some examples, the
controller 62 is not limited to any specific combination of
hardware circuitry and machine readable instructions (including
software), nor limited to any particular source for the machine
readable instructions executed by the controller 62.
[0028] With this in mind, in general terms the therapy manager 72
acts to synthesize respiratory information, to determine suitable
stimulation parameters based on that respiratory information, and
to direct electrical stimulation to the target nerve.
[0029] In one example, among other components, therapy manager 72
includes a stimulation protocol determination module 74.
[0030] In one example, the stimulation protocol determination
module 74 includes an input function 76 and a selector function 78.
In general terms, the input function receives an indication of an
upper airway flow limitation that is sensed via respiratory effort
information. In one example, input function 76 includes a flow
limitation parameter 80 and a respiratory effort parameter 82.
[0031] In one example, the flow limitation parameter 80 detects and
tracks when a flow limitation is present in the upper airway of a
patient. In one aspect, the flow limitation parameter 80 tracks the
degree and/or duration of flow limitation. Various examples of
recognizing a flow limitation are further described below in
association with at least FIGS. 3-13.
[0032] In one example, the respiratory effort parameter 82 detects
and tracks respiratory effort information obtained via sensing
respiratory information such as, but not limited to, the
respiratory sensing methods previously described above in
association with FIGS. 1A-1B. This respiratory effort information
corresponds to air flow and enables constructing or determining a
degree and/or duration of a flow limitation in the upper airway of
a patient.
[0033] As noted above, the therapy manager 72 also includes a
selector function 78, which in general terms, enables the IPG 60 to
select an appropriate stimulation protocol that is responsive to a
particular type of upper airway flow limitation. In one example,
the selector function 78 includes a respiratory phase parameter 84
and a protocol array parameter 86. The respiratory phase parameter
84 determines which respiratory phase or phases, or portions of the
respective phases, in which stimulation should be applied. In one
aspect, these determinations are made based on the ongoing sensing
of respiratory effort, with the sensed information being received
by input function 76.
[0034] The protocol array parameter 86 provides an array of
stimulation protocols suitable for delivering to a nerve of a
patient, depending upon the type, degree, and/or duration of a flow
limitation. The protocol array parameter 86 does so in cooperation
with respiratory phase parameter 84 and input function 76.
[0035] Specific examples of treating disordered breathing via the
therapy manager 72, and in particular, treating upper airway flow
limitations (i.e. obstructions) via the functions, components,
parameters, and/or features of protocol determination module 74 of
therapy manager 72 are further described and illustrated below in
association with FIGS. 3-13.
[0036] In general terms, the stimulation module 68 of IPG 60 is
configured to generate and apply a neuro-stimulation signal via
electrode(s) (such as stimulation electrode(s) 45 in FIG. 1A)
according to a treatment regimen programmed by a physician and/or
in cooperation with therapy manager 72, such as via protocol
determination module 74.
[0037] In general terms, the patient management module 70 is
configured to facilitate communication to and from the IPG 60 in a
manner familiar to those skilled in the art. Accordingly, the
patient management module 70 is configured to report activities of
the IPG 70 (including sensed physiologic data, stimulation history,
number of apneas detected, etc.) and is configured to receive
initial or further programming of the IPG 60 from an external
source, such as a patient programmer, clinician programmer,
etc.
[0038] In one example, as shown in FIG. 1C, prior to applying
stimulation to maintain and/or restore patency in the upper airway,
at 102 the method 100 includes identifying a pattern of flow
limitation during the respiratory cycle. In one aspect, method 100
identifies the circumstances in which a flow limitation primarily
occurs. In particular, with further reference to FIG. 1, method 100
distinguishes between a flow limitation occurring: (1)
predominantly during inspiration (at 104); (2) predominantly during
expiration (at 106); or (3) during both a portion of inspiration
and a portion of expiration which acts as a mixed flow limitation
(at 108). In one aspect, in the context of the present disclosure,
a flow limitation corresponds to a narrowing of the upper airway of
the type typically associated with obstructive sleep apnea or other
disordered breathing patterns, as familiar to those skilled in the
art.
[0039] As shown in FIG. 1C, in one example, in the event that the
flow limitation occurs predominantly during inspiration (at 104),
then stimulation is applied during and/or synchronized with
inspiration (at 110). On the other hand, in another example, in the
event that the flow limitation occurs predominantly during (i.e.
coincides with) expiration (at 106), and then stimulation is
applied during and/or synchronized with expiration (at 112).
[0040] However, in some examples, when the flow limitation occurs
predominantly during (i.e. coincides with) a portion of inspiration
and a portion of expiration (at 108), the stimulation is applied
during some portion of inspiration and some portion of expiration
(at 114).
[0041] In one example, when the flow limitation overlaps the
transition between the end of inspiration and the beginning of
expiration, the stimulation will be applied to overlap the
transition between the end of inspiration and the beginning of
expiration.
[0042] In another example, when the flow limitation occurs during a
portion of inspiration and a portion of expiration (at 108), the
stimulation is applied to cover an entire respiratory cycle,
including an entire inspiratory phase and an entire expiratory
phase.
[0043] In order to recognize a flow limitation, the method 100 uses
as a reference point a normal breathing pattern 150, as shown in
FIG. 2. Of course, variances may exist from patient-to-patient so
it will be understood that the normal breathing pattern 150 is a
representative example provided for illustrative purposes and is
not intended to strictly define a breathing pattern that is
universally normal for all patients. With this in mind, in some
embodiments, the method 100 uses the particular breathing pattern
of a specific patient (to which the method is applied) as the
reference point to evaluate the presence or absence of a flow
limitation in breathing.
[0044] In the example of normal breathing pattern 150 shown in FIG.
2, a respiratory cycle 160 includes an inspiratory phase 162 and an
expiratory phase 170. The inspiratory phase 162 includes an initial
portion 164, intermediate portion 165, and end portion 166 while
expiratory phase 170 includes an initial portion 174, intermediate
portion 175, end portion 176, and an expiratory peak 177. A first
transition 180 occurs at a junction between the end inspiratory
portion 166 and the initial expiratory portion 174 while a second
transition 182 occurs at a junction between the end expiratory
portion 176 and the initial inspiratory portion 164.
[0045] In one example, the various stimulation protocols described
and illustrated in association with FIGS. 3-13 are implemented via
system 10 (FIG. 1A) and/or IPG 60 (FIG. 1B) including at least
therapy manager 72 and/or protocol determination module 74.
However, in another example, the various stimulation protocols
described and illustrated in association with FIGS. 3-13 are
implemented via other component, modules, and systems.
[0046] FIG. 3 is a diagram 200 illustrating a disordered breathing
pattern 203A and treated breathing pattern 203B (separated by
dashed line 203C), according to one embodiment of the present
disclosure. As shown in FIG. 3, disordered breathing pattern 203A
reflects the presence of a flow limitation in the upper airway that
occurs predominantly during the inspiratory phase of a respiratory
cycle. The inspiratory phase 202A includes an initial portion 204A,
an intermediate portion 205A, and an end portion 206A while the
expiratory phase 210A includes an initial portion 214A,
intermediate portion 215A, peak 217A, and end portion 216A. In one
aspect, intermediate portion 205A of inspiratory phase 202A forms a
generally flat or horizontal shape corresponding to a substantially
truncated amplitude (as compared to a normal breathing pattern,
such as FIG. 2) and that reflects the occurrence of a flow
limitation (symbolically represented by arrow 201) in the upper
airway during inspiration. However, via application of stimulation
(symbolically represented by bar 221), breathing is restored as
represented by treated breathing pattern 202B in which intermediate
portion 205B of inspiratory phase 202B resumes a generally
parabolic shape corresponding to a generally normal amplitude and
that represents amelioration of the flow limitation. In one
embodiment, the stimulation is represented by bar 221, which
extends from a first end 222 to a second end 224, with the
stimulation substantially coinciding with the entire duration of
the inspiratory phase 202B. As shown in FIG. 3, the stimulation 221
terminates prior to the expiratory phase 210B. However, as will be
explained in more detail below, in other embodiments, the applied
stimulation does not extend the entire duration of inspiratory
phase 202B but is applied to select portions of the inspiratory
phase 202B.
[0047] It will be understood that, in one example, the detection of
flow limitations and/or associated apneas), as well as the
detection of the beginning and end of the respective inspiratory
and expiratory phases of the respiratory cycle to enable
determining when to stop or start stimulation, is performed
according to, or in cooperation with, known methods and devices for
doing so. Some non-limiting examples of such devices and methods to
recognize and detect the various features and patterns associated
with respiratory effort and flow limitations include, but are not
limited to: PCT Publication WO/2010/059839, titled A METHOD OF
TREATING SLEEP APNEA, published on May 27, 2010; Christopherson
U.S. Pat. No. 5,944,680, titled RESPIRATORY EFFORT DETECTION METHOD
AND APPARATUS; and Testerman U.S. Pat. No. 5,522,862, titled METHOD
AND APPARATUS FOR TREATING OBSTRUCTIVE SLEEP APNEA.
[0048] FIG. 4 is a diagram 250 illustrating a disordered breathing
pattern 253A and treated breathing pattern 253B, according to one
embodiment of the present disclosure. As shown in FIG. 4,
disordered breathing pattern 253A reflects the presence of a flow
limitation in the upper airway that occurs predominantly during the
expiratory phase of a respiratory cycle. In the disordered
breathing pattern 253A, the inspiratory phase 252A includes an
initial portion 254A, an intermediate portion 255A, and an end
portion 256A, with the inspiratory phase 252A exhibiting a
generally normal breathing pattern 150 (FIG. 2). Referring again to
FIG. 4, the expiratory phase 262A includes an initial portion 264A,
intermediate portion 265A, peak 267A, and end portion 266A. In one
aspect, expiratory phase 262A has a relatively shallow peak 267A
corresponding to an amplitude or peak pressure that is
substantially smaller than a peak 177 of an expiratory phase 170 in
a normal breathing pattern 150 (FIG. 2). The pattern of expiratory
phase 262A, which corresponds to a generally shallow expiration,
reflects the occurrence of a flow limitation (symbolically
represented by arrow 251) in the upper airway during expiration.
Moreover, because the peak 267A is so shallow, the intermediate
portion 265A in the expiratory phase 262A has a relatively gradual
upward slope instead of the generally steep upward slope present in
the intermediate portion 175 in the normal expiratory phase 170 (of
a normal breathing pattern 150 in FIG. 2).
[0049] However, as shown in FIG. 4, via application of stimulation
(symbolically represented by bar 270), the expiratory phase 262B
becomes corrected such that peak 267B resumes its full amplitude
and intermediate portion 265B of expiratory phase 262B is restored
to a generally steep upward slope, both of which represents
amelioration of the flow limitation. In one embodiment, the
stimulation (270) is represented by bar 271 (which extends from a
first end 272 to a second end 274) and substantially coincides with
the entire duration of the expiratory phase 262B. However, as will
be explained in more detail below, in other embodiments, the
applied stimulation extends only part of the duration of expiratory
phase 262B.
[0050] In one embodiment, application of the stimulus occurs at an
inspiratory phase (FIG. 3) or at an expiratory phase (FIG. 4),
respectively, of every respiratory cycle. However, in other
embodiments, application of the stimulus is applied selectively to
just some respiratory cycles, as needed, in association with an
auto-titration method. One example of such auto-titration methods
include A METHOD OF TREATING SLEEP APNEA as described and
illustrated in PCT Publication WO/2010/059839, published on May 27,
2010.
[0051] FIG. 5A is a diagram 280 illustrating a disordered breathing
pattern 283A and treated breathing pattern 283B, according to one
embodiment of the present disclosure. As shown in FIG. 5A,
disordered breathing pattern 283A represents a flow limitation in
the upper airway that occurs during both a portion of an
inspiratory phase 282 and a portion of the expiratory phase 292 of
a respiratory cycle. As shown in FIG. 5A, the inspiratory phase
282A includes an initial portion 284A, an intermediate portion
285A, and an end portion 286A while the expiratory phase 292A
includes an initial portion 294A, intermediate portion 295A, peak
297A, and end portion 296A.
[0052] In one aspect, FIG. 5A illustrates that in disordered
breathing pattern 283A, intermediate portion 285A of inspiratory
phase 282A forms a generally flat or horizontal shape corresponding
to a substantially truncated amplitude (as compared to the
inspiratory phase 162 of a normal breathing pattern 150, such as
FIG. 2), with this generally flat shape reflecting the occurrence
of a flow limitation (symbolically represented by arrow 281A) in
the upper airway during inspiration.
[0053] In another aspect, disordered breathing pattern 283A also
includes an expiratory phase 292A having a peak 297A corresponding
to an amplitude or peak pressure that is substantially smaller than
a peak 177 of an expiratory phase 170 in a normal breathing pattern
150 (FIG. 2). This pattern 283A, which corresponds to generally
shallow expiration, results from a flow limitation (symbolically
represented by arrow 281B) in the upper airway during expiration.
Moreover, because the peak 297A is so shallow, the intermediate
portion 295A has a relatively gradual upward slope instead of the
generally steep upward slope present in the intermediate portion
175 in the normal expiratory phase 170 (of a normal breathing
pattern 150 in FIG. 2).
[0054] In one example, the indicated upper airway flow limitation
predominantly coincides with both of a first portion of the
inspiratory phase and a first portion of the expiratory phase. In
another aspect, this indicated flow limitation does not
predominantly coincide with a second portion of inspiratory phase
and with a second portion of the expiratory phase.
[0055] However, via application of blended stimulation
(symbolically represented by bar 300) directed to at least a
portion of the inspiratory phase and a portion of the expiratory
phase, the flow limitations are mitigated. As shown in treated
breathing pattern 283B, a latter segment 285C of intermediate
portion 285B (and end portion 286B) resumes a more parabolic shape
better resembling a baseline inspiratory phase prior to the flow
limitation and that corresponds to amelioration of the
"inspiratory" flow limitation.
[0056] Likewise, because this stimulation overlaps from the
inspiratory phase 282B into the expiratory phase 292B, the treated
breathing pattern 283B exhibits a peak 297B approaching a baseline
amplitude prior to the flow limitation (like amplitude 177 in the
expiratory phase 170 of normal breathing pattern 150 of FIG. 2).
This treated breathing pattern 283B also exhibits an intermediate
portion 295B that is restored to steeper upward slope amplitude,
both of which represents amelioration of the "expiratory" flow
limitation.
[0057] In one embodiment, the stimulation is represented by bar
300, which extends from a first end 301 (in the inspiratory phase
282B) to a second end 303 (in the expiratory phase 292B). The
stimulation is applied as a generally continuous stimulation period
that is initiated (at a start point located away from a beginning
portion 284B of the inspiratory phase 252B) from partway through
the intermediate portion 285B and through the end portion 285C of
the inspiratory phase 282B, through the transition from inspiration
to expiration, through the initial portion 294B and peak 297A of
the expiratory phase 292B, and at least partway through the
intermediate portion 295B of the expiratory phase 292B (to a
termination point prior to end portion 296B of expiratory phase
292B).
[0058] In one example, the embodiment of FIG. 5A addresses the
situation for some patients in which the greatest risk for airway
collapse appears to occur near the end of inspiration and the
beginning of expiration. In these instances, besides harmfully
limiting a duration and volume of inspiration, a partially
restricted upper airway throughout the inspiratory phase
predisposes the upper airway to be more susceptible to further
collapse at the end of the inspiratory phase and/or to the
beginning of the expiratory phase. Accordingly, in the embodiment
of FIG. 5A, the blended stimulation (represented by bar 300) begins
at start point approximately midway through the inspiratory phase
282B and extends substantially continuously through a transition
between the end of inspiration and the beginning of expiration
until reaching a termination point approximately midway through the
expiratory phase 292B. In one aspect, this blended stimulation is
terminated after a bulk of the expiration would have been expected
to occur. In this way, continuous stimulation of the hypoglossal
nerve through complete respiratory cycles is avoided, which in
turn, minimizes unnecessary stimulation of the hypoglossal nerve.
Instead, in these embodiments, stimulation is applied strategically
in targeted portions of one or more respiratory cycles to prevent
upper airway collapse so that stimulation is applied more
judiciously while still achieving efficacious results.
[0059] Further, it will be understood that diagram 280 in FIG. 5A
provides just one example schematically illustrating the
application of a blended stimulation that overlaps the end of the
inspiratory phase and the beginning of the expiratory phase.
[0060] Accordingly, applying this blended stimulation overcomes
expiratory narrowing, which otherwise might render the upper airway
vulnerable to complete collapse during a subsequent inspiratory
effort.
[0061] Without being bound to any particular theory, it is believed
that the blended stimulation that overlaps the end of inspiratory
phase and the expiratory phase acts to maintain a minimum level of
pressurization within the lungs, which in turn helps maintain
airway patency because the minimum level of pressurization helps to
prevent a high intensity vacuum from the lungs on the airway, which
would otherwise potentially cause collapse of the upper airway.
[0062] In this way, for some patients, the stimulation is applied
during a period having a higher risk for collapse without having to
continuously apply stimulation through the entire respiratory
cycle, which in turn, saves energy and minimizes potentially
unnecessary stimulation of the nerves.
[0063] In one example of a stimulation protocol, such as the one
described and illustrated in association with FIG. 5A, the
generally continuous stimulation period (as represented by bar 300
in FIG. 5A and spanning over a portion of the inspiratory phase and
a portion of the expiratory phase) is applied to a set of
consecutive respiratory cycles over a first time period. Moreover,
an input module (such as input module 76 of protocol determination
module 74 of therapy manager 72 in FIG. 1B) is configured to
evaluate whether flow limitations are persisting despite the
stimulation protocol or whether the stimulation protocol has
mitigated or eliminated the previously occurring flow limitations.
Accordingly, in one aspect, the input module of the therapy manager
determines if at least some indications of upper airway flow
limitations are received within the first time period. In another
aspect, the input module of the therapy manager increases a
duration of the generally continuous stimulation period if the
input module receives the at least some indications during the
first time period when such indications exceed a threshold. In
another aspect, the input module of the therapy manager reduces the
duration of the generally continuous stimulation period if the
input module receives no indications of upper airway flow
limitations (or a number of indications less than a threshold)
during the first time period.
[0064] In one example, the first time period (over which the set of
respiratory cycles take place) is a duration, based on an
apnea-hypopnea index of a patient, in which an apnea would be
expected to occur in the absence of stimulation.
[0065] FIG. 5B is a diagram schematically illustrating portions of
a generally continuous stimulation period relative to portions of
an inspiratory phase and an expiratory phase, according to one
example of the present disclosure.
[0066] As a reference point for illustrating the generally
continuous stimulation period, FIG. 5B provides substantially the
same depiction of a respiratory cycle 160 that was previously shown
in FIG. 1. Accordingly, the illustrated respiratory cycle 160
includes an inspiratory phase 162 and an expiratory phase 170. The
inspiratory phase 162 includes an initial portion 164, intermediate
portion 165, and end portion 166 while expiratory phase 170
includes an initial portion 174, intermediate portion 175, end
portion 176, and an expiratory peak 177. A first transition 180
occurs at a junction between the end inspiratory portion 166 and
the initial expiratory portion 174 while a second transition 182
occurs at a junction between the end expiratory portion 176 and the
initial inspiratory portion 164.
[0067] According to one example of the present disclosure, FIG. 5B
further illustrates a first bar 361 that represents a first portion
360 of a generally continuous stimulation period 358 and a bar 381
that represents a second portion 380 of a generally continuous
stimulation period 358. As shown in FIG. 5B, the bar 361 includes
first end 362 that generally coincides with junction 180 (the end
of inspiratory phase 162 and beginning of expiratory phase 170) and
a second end 364 located in an intermediate portion of the
inspiratory phase 162. As shown in FIG. 5B, bar 381 includes first
end 382 that generally coincides with junction 180 (the end of
inspiratory phase 162 and beginning of expiratory phase 170) and a
second end 384 located in an intermediate portion of the expiratory
phase 170.
[0068] As further demonstrated by FIG. 5B, while the generally
continuous stimulation period overlaps the inspiratory and
expiratory phases 162, 170, the duration of each of the first and
second portions of the generally continuous stimulation period can
vary among different nerve stimulation protocols as determined by
the protocol determination module 74 of therapy manager 72 (FIG.
1B).
[0069] In one example, the first portion 360 of the generally
continuous stimulation period 358 has a duration of at least
one-third (identified by marker 372) of an entirety (El) of the
inspiratory phase 162. In one aspect, the relative proportion of
one-third is measured starting at end 362 of bar 361, per
directional reference arrow 357. In another example, the first
portion 360 of the generally continuous stimulation period 358 has
a duration of at least one-half (identified by marker 370) of the
entirety (E1) of the inspiratory phase 162. In another example, the
first portion 360 of the generally continuous stimulation period
358 has a duration of at least two-thirds (identified by marker
374) of the entirety (E1) of the inspiratory phase 162
[0070] In another example, the second portion 380 of the generally
continuous stimulation period 358 has a duration of at least
one-third (identified by marker 392) of an entirety (E2) of the
expiratory phase 170. In one aspect, the relative proportion of
one-third is measured starting at end 382 of bar 381, per
directional reference arrow 377. In another example, the first
portion 380 of the generally continuous stimulation period 358 has
a duration of at least one-half (identified by marker 390) of the
entirety (E2) of the expiratory phase 170. In another example, the
first portion 380 of the generally continuous stimulation period
358 has a duration of at least two-thirds (identified by marker
393) of the entirety (E2) of the expiratory phase 170.
[0071] In one example, the first portion (during which stimulation
is applied) of the inspiratory phase 162 corresponds to at least a
majority of an entirety (El) of the inspiratory phase 162 and the
first portion (during which stimulation is applied) of the
expiratory phase 170 corresponds to at least a majority of an
entirety (E2) of the expiratory phase 170. In one example, a
majority is defined as at least fifty-one percent (i.e. 51%). In
another example, the majority of the inspiratory phase 162 is
defined as an at least two-thirds majority of the entirety (E1) of
the inspiratory phase 162 and the majority of the expiratory phase
is defined as an at least two-thirds majority of the entirety (E2)
of the expiratory phase 170.
[0072] In one example, variations on the stimulation protocol
associated with FIGS. 5A and 5B are further described later in
association with at least FIGS. 6 and 11.
[0073] In another embodiment, as shown in FIG. 6, diagram 310
schematically illustrates a disordered breathing pattern 333A
resulting from a mixed flow limitation that is substantially
similar to the mixed flow limitation in FIG. 5A. However, unlike
the substantially continuous segment of stimulation 300 applied in
FIG. 5A, in the embodiment shown in FIG. 6, stimulation is applied
in two separate relatively short bursts 340, 342. One burst 340 is
applied at the beginning of the inspiratory phase 322B while the
other burst 342 is applied at the beginning of the expiratory phase
332B. In this embodiment, the stimulation is targeted to anticipate
an obstruction, and in turn, apply stimulation at the beginning of
one or both of the respective inspiratory and expiratory phases. By
stimulating (for a short duration) at the beginning of a respective
inspiratory and expiratory phases, the upper airway is held open
prior to the maximum flow of air in that phase so that once the
flow of air commences, with the upper airway already open to a
generally full degree, the inspired or expelled air (respectively)
completes the job of maintaining the upper airway in the open state
during the remainder of the respective inspiratory or expiratory
phase. In another aspect, one potential benefit from applying a
stimulation burst at the beginning of an inspiratory phase is the
resulting counteraction of the negative pressure (generated by the
inspiratory effort) applied to the upper airway.
[0074] Without being bound to any particular theory, it is believed
that by applying a stimulation burst (e.g., an additional
stimulation burst on top of a baseline level of stimulation or an
isolated burst of stimulation without a baseline level of
stimulation) at the beginning of the inspiratory phase, the
stimulation causes or ensures radial expansion of the airway at the
very time that a high intensity vacuum would be applied (via the
lungs) to the upper airway such that the radial expansion of the
upper airway (caused by the stimulation burst) directs action or
response of tissues in a direction opposite the action of tissue
that would might otherwise occur when the vacuum from lungs acts on
the upper airway tissues. Accordingly, the stimulation is timed to
produce momentum in the tissues of the upper airway toward radial
expansion prior to the high intensity vacuum pull (which might
otherwise contribute to collapse of the upper airway) from the
lungs during the onset of inspiration. Because there is a delay
associated with, or caused by, a time constant in the response of
the upper airway tissues, by first stimulating the tissue in
advance of the vacuum pull from the lungs, enough momentum is
established toward radial expansion of the upper airway via the
stimulation burst that this momentum counteracts or
prophylactically negates the otherwise potentially collapsing
effects of the vacuum pull on the upper airway tissues.
[0075] In one aspect, by applying stimulation in this manner, it is
believed that airway patency is maintained with less overall
stimulation being applied because stimulation is applied
strategically within one or more respiratory cycles rather than
indiscriminately through entire respiratory cycles. With this in
mind, in one embodiment the total combined duration of burst 340
and burst 342 (shown in FIG. 6) is substantially less than the
duration of the stimulation pulse 300 in FIG. 5A. Accordingly,
adequate airway patency is achieved while significantly reducing
the total volume of stimulation applied to the nerve.
[0076] In some embodiments in which separate bursts of stimulation
are applied to the inspiratory and expiratory phases, respectively,
the duration of the bursts in the inspiratory phase differ from the
duration of the burst applied in the expiratory phase. For example,
as shown in the diagram 400 of FIG. 7A, a representative or normal
breathing pattern 401 is maintained by applied stimulation. A
stimulation burst (represented by bar 420A) of a first duration is
applied at the beginning of the inspiratory phase 402A while a
second stimulation burst (represented by bar 422A) is applied
during substantially the entire expiratory phase 412A. This pattern
of stimulation bursts is repeated throughout successive respiratory
cycles 402B, 402C, etc.
[0077] In one aspect, the determination regarding the duration of
each "inspiratory phase" burst (420A, 420B, 420C) and the duration
of each "expiratory phase" burst (422A, 422B, 422C) can vary from
patient-to-patient depending upon whether the particular patient
tends to exhibit a greater flow limitation in the inspiratory phase
403A or in the expiratory phase 413A. In the example, shown in FIG.
7A, the "expiratory phase" bursts (422A, 422B, 422C) have a longer
duration than the "inspiratory phase" bursts (420A, 420B, 420C) to
treat a patient that generally exhibits a mixed flow limitation
(both inspiratory and expiratory) but having greater flow
limitations during the expiratory phase.
[0078] In one embodiment, anyone of or all of an amplitude, a pulse
width, a frequency of applied stimulation during the inspiratory
phase is different than anyone of (or all of) an amplitude, a pulse
width, a frequency of applied stimulation during the expiratory
phase. In addition, a ramped stimulation pattern in which
stimulation ramps upward (increases) at the beginning of a
stimulation period or ramps downward at the end of a stimulation
period, can be applied in one or both of the inspiratory and
expiratory phases.
[0079] In some embodiments, as shown in FIG. 7B, instead of
applying a stimulation burst with each respiratory cycle, the
stimulation bursts (e.g. 420A, 420C, 422A, 422C) are applied every
other respiratory cycle, such that an intermediate "inspiratory
phase" burst 422A and an intermediate "expiratory phase" burst 422B
are omitted. In this embodiment, the patient need not receive a
stimulation burst each respiratory cycle because with this
stimulation pattern the patient receives enough oxygen to keep the
respiratory drive in equilibrium. In another embodiment, the
pattern of stimulation bursts in the inspiratory phase (applied
every respiratory cycle, such as 420A, 420B, 420C) need not be
matched by the pattern of stimulation bursts in the expiratory
phase (applied every other respiratory cycle, such as 422A and
422C), or vice versa. In this way, the upper airway remains patent
and the patient receives sufficient oxygen without receiving
stimulation in each inspiratory phase or in each expiratory
phase.
[0080] In yet other embodiments, other forms of alternating
stimulation bursts are applied. For example, in one pattern of
stimulation, a low amplitude continuous pulsed stimulation is
applied and one or more relatively shorter duration stimulation
bursts are applied in a targeted and additive manner to the low
amplitude continuous stimulation. FIG. 8 is a diagram 450
schematically illustrating a method of treating sleep disordered
breathing via a stimulation pattern, according to one embodiment of
the present disclosure. As shown in FIG. 8, a respiratory cycle 453
includes an inspiratory phase 451 and an expiratory phase 461. The
inspiratory phase 451 includes an initial portion 454, an
intermediate portion 455, and an end portion 456 while the
expiratory phase 461 includes an initial portion 464, intermediate
portion 465, peak 467, and end portion 466.
[0081] As further shown in the diagram 450 of FIG. 8, a low
amplitude continuous pulsed stimulation (represented by bar 470) is
applied in the inspiratory phase 451 and a low amplitude pulsed
continuous stimulation (represented by bar 480) in the expiratory
phase 461. While bars 470, 480 are shown as separate elements for
illustrative purposes, it will be understood that the generally
continuous stimulation is substantially uninterrupted through the
transition from the inspiratory phase 451 to the expiratory phase
461. In addition, as shown in FIG. 8, a shorter duration
stimulation burst 475 is applied only in the inspiratory phase 451
(for patients having predominantly inspiratory-based flow
limitations) in addition to the generally continuous pulsed lower
amplitude tone stimulation 470. While the additional stimulation
burst 475 could be applied anywhere within the inspiratory phase
451, in the example shown in FIG. 8, the burst is applied at the
initial portion 454 of the inspiratory phase 451. In one aspect,
applying the burst at the initial portion 454 helps to ensure full
patency of the upper airway as inspiration begins because the
stimulation causes a response like the action of a virtual stent in
the upper airway to pre-establish patency prior to the vacuum pull
from the lungs. As previously noted, the initial portion of
stimulation (during a peak pressure period) effectively establishes
momentum of the upper airway to be moving in direction of expansion
(radially outward) such that upon a vacuum applied via the lungs
during inspiration, the upper airway tends to stay expanded because
response of tissue is slow enough such that the vacuum (generated
by the lungs) cannot fully overcome the already established
momentum of radial expansion of the upper airway and therefore the
initial portion of stimulation prevents collapse of the upper
airway.
[0082] Without being bound by any particular theory, it is believed
that using a burst of stimulation (for example, burst 475 in FIG.
8) helps to keep blood oxygenation levels and carbon dioxide levels
within an acceptable range, which in turn moderates the respiratory
drive, which in turn minimizes peak respiratory pressures.
Together, these factors minimizes the risk of an upper airway
collapse because the lungs are not forced (via the respiratory
drive) to exert extra vacuum pressure on an upper airway in an
attempt to acquire more oxygen.
[0083] In one embodiment, the stimulation pattern in FIG. 8 is
modified, such that the modified pattern omits the base level of
generally continuous stimulation 470 in the inspiratory phase 451,
leaving just one or more stimulation bursts 475 in the inspiratory
phase 451. Meanwhile, the modified pattern retains the base level
stimulation 480 during the expiratory phase 461, which effectively
acts to maintain tone and patency of the upper airway during the
expiratory phase 461.
[0084] FIG. 9 is a diagram 500 schematically illustrating a method
of treating sleep disordered breathing via a stimulation pattern
that is modified relative to the stimulation pattern of FIG. 8,
according to one embodiment of the present disclosure. As shown in
FIG. 9, a respiratory cycle 503 includes an inspiratory phase 501
and an expiratory phase 511. The inspiratory phase 501 includes an
initial portion 504, an intermediate portion 505, and an end
portion 506 while the expiratory phase 511 includes an initial
portion 514, intermediate portion 515, peak 517, and end portion
516. As further shown in diagram 450 of FIG. 9, a shorter duration
stimulation burst 535 is applied only in the expiratory phase 511
(for patients having predominantly expiratory-based flow
limitations) in addition to the generally continuous pulsed lower
amplitude tone stimulation 530. In particular, as shown in FIG. 8,
a low amplitude pulsed continuous stimulation (represented by bar
520) is applied in the inspiratory phase 501 and a low amplitude
continuous stimulation (represented by bar 530) in the expiratory
phase 511. While the additional stimulation burst 535 could be
applied anywhere within the expiratory phase 511, in the example
shown in FIG. 9, the burst is applied at the initial portion 514
and peak portion 517 of the expiratory phase 511 to ensure full
patency during peak expiration. In another aspect, in this
arrangement the low level generally continuous stimulation 530 and
burst 535 are applied at the point at which the patient has
exhibited the most significant flow limitations in the upper
airway.
[0085] FIG. 10 is a diagram 550 schematically illustrating a method
of treating sleep disordered breathing via a stimulation pattern
that is modified relative to the stimulation pattern of FIG. 8,
according to one embodiment of the present disclosure. As shown in
FIG. 10, a respiratory cycle 503 includes an inspiratory phase 501
and an expiratory phase 511. The inspiratory phase 501 includes an
initial portion 504, an intermediate portion 505, and an end
portion 506 while the expiratory phase 511 includes an initial
portion 514, intermediate portion 515, peak 517, and end portion
516.
[0086] As further shown in FIG. 10, the stimulation pattern of FIG.
8 is modified so that one additional stimulation burst 560 (in
addition to the lower amplitude continuous stimulation 520) is
applied at the latter portion of the inspiratory phase 501 and one
additional stimulation burst 535 is applied at the initial portion
514 and peak portion 517 of the expiratory phase 511 (in
substantially the same manner as in diagram 500 of FIG. 8). In this
embodiment, the two bursts 560, 535 of stimulation mimic the
stimulation pattern in FIG. 5 with the overall stimulation pattern
also including the low level generally continuous stimulation 520,
530 throughout both the inspiratory and expiratory phases 501,
511.
[0087] In some embodiments, the moment at which stimulation burst
is initiated (within a given inspiratory phase or give expiratory
phase) is optimized so that no surplus stimulation is applied. For
example, in an example in which a patient has a mixed flow
limitation, and a single longer stimulation burst is applied that
overlaps both the inspiratory phase and the expiratory phase (such
as shown in FIG. 5), an auto-titrating method is applied in which a
start point is selected for initiating stimulation during the
inspiratory phase and a termination point is selected for
terminating stimulation during the expiratory phase.
[0088] With further reference to FIGS. 8-10 and 13, it will be
understood that adjusting the stimulation amplitude is just one way
of modulating the intensity of stimulation, and that in other
embodiments, the stimulation intensity is modulated via adjusting
the frequency, pulse width, duration, polarity, etc. of pulsed
stimulation. For example, instead of applying a stimulation burst
of increase amplitude (such as burst 475 in FIG. 8 or burst 535 in
FIG. 9), the stimulation burst can include an increased pulse
width, increased frequency, or change in polarity.
[0089] FIG. 11 shows a diagram 600 schematically illustrating a
method of treating disordered breathing, according to one
embodiment of the present disclosure. As shown in FIG. 11, a
respiratory cycle 603 includes an inspiratory phase 601 and an
expiratory phase 611. The inspiratory phase 601 includes an initial
portion 604, an intermediate portion 605, and an end portion 606
while the expiratory phase 611 includes an initial portion 614,
intermediate portion 615, peak 617, and end portion 616. As shown
in diagram 600 of FIG. 11, an initial start point for stimulation
630 is identified (point A) and an initial termination point of
stimulation 640 is identified (point F). It will be understood that
in at least one example, stimulation segments 630,640 are shown as
separate elements for illustrative clarity, and that in fact
segments 630, 640 represent a single substantially continuous
period of stimulation.
[0090] Using these parameters, therapy is applied through a period
of time to observe whether the applied stimulation is efficacious.
In the event that the stimulation period (segments 630 and 640)
within the respiratory cycle is sufficient to ameliorate the sleep
disordered breathing, the method begins to scale back the total
duration of the stimulation period (segments 630, 640).
Accordingly, the start point of stimulation segment 630 is moved to
point B, corresponding to a shorter period of stimulation (in the
inspiratory phase 601), and therapy is applied for a period of many
respiratory cycles while observing whether the shortened duration
of stimulation is efficacious. This adjustment process is continued
in which the duration of stimulation segment 630 in the inspiratory
phase 601 is reduced one step at a time (as represented by
directional arrow R), until a start point (e.g. A, B, C, D, E,
etc.) is identified at which the inspiratory-phase stimulation
segment 630 becomes too short as evidenced by the stimulation
starting to lose its effectiveness in maintaining and/or restoring
airway patency. In other words, the start point is moved in
decrements closer to the end portion of the inspiratory phase until
a loss of efficacious stimulation therapy is identified.
[0091] In one example, once the start point has been adjusted by a
decrement (one step), the new duration is maintained for a set of
consecutive respiratory cycles to provide a sufficient period of
time over which to evaluate the new settings.
[0092] With this information, one can identify the last initiation
point at which the desired effectiveness was achieved, and this
point is adopted as the optimal start point for stimulation segment
630 in the inspiratory phase 610 for this patient. For example, if
the start point D resulted in a stimulation segment 630 that proved
ineffective in maintaining or restoring airway patency, while start
point C was the last successful start point, then the optimal
stimulation segment 630 would have a start point C. Once the
optimal start point is adopted, each stimulation segment 630 within
a give respiratory cycle 603 would begin at start point C.
[0093] In one example, the size of the decrements or steps between
the respective start points (A, B, C, etc.) correspond to a
fraction (such as 1/10, 1/5, or 1/8, etc. of the entire duration of
the first portion 360 of the stimulation period 358.
[0094] In another example, the initial starting point (e.g. A) is
selected to correspond to one of the example durations (two-thirds,
one-half, or one-third) of the first portion 360 of the generally
continuous stimulation period 358 shown in FIG. 5B.
[0095] A similar method is applied to the expiratory phase 611 such
that the optimal termination point of the stimulation period
(segments 630 and 640) is determined for a given respiratory cycle.
In doing so, an initial termination point (e.g. point F) for
stimulation segment 640 is identified, and therapy is applied.
Provided that efficacy was achieved, the method continues by
adopting an earlier termination point (e.g. point G), corresponding
to a shorter period of stimulation (in the expiratory phase 611),
and therapy is applied for a period of time covering many
respiratory cycles. The response of the patient is observed to
determine if any loss of efficacy has occurred due to shortening
the stimulation segment 640. This process is continued in which the
duration of stimulation 640 in the expiratory phase 611 is reduced
one step at a time (as represented by directional arrow T), until a
termination point (anyone of points F, G, H, I, J, K, etc.) is
identified at which the expiratory-phase stimulation 640 becomes
too short as evidenced by the stimulation starting to lose its
effectiveness in maintaining and/or restoring airway patency. In
other words, the termination point is moved in decrements closer to
the beginning portion of the expiratory phase until a loss of
efficacious stimulation therapy is identified.
[0096] With this information, one can identify the last termination
point at which the desired effectiveness was achieved, and this
point is adopted as the optimal termination point of stimulation
segment 640 for this patient to overcome the mixed flow limitation
(i.e. a flow limitation that overlaps both the inspiratory and the
expiratory phases 601, 611).
[0097] In one example, once the termination point has been adjusted
by a decrement (one step), the new duration is maintained for a set
of consecutive respiratory cycles to provide a sufficient period of
time over which to evaluate the new settings.
[0098] In one example, the size of the decrements or steps between
the respective termination points (F, G, H, etc.) corresponds to a
fraction (such as 1/10, 1/5, or 1/8, etc. of the entire duration of
the second portion 380 of the stimulation period 358.
[0099] In another example, the initial starting point (e.g. F) is
selected to correspond to one of the example durations (two-thirds,
one-half, or one-third) of the second portion 380 of the generally
continuous stimulation period 358 shown in FIG. 5B.
[0100] It will be understood, that in addition to optimizing the
duration of the stimulation segments 630, 640 shown in association
with FIG. 11, one also can optimize for other parameters of the
stimulation, such as amplitude, polarity, frequency, pulse width,
etc., where an increase or decrease in amplitude, frequency, pulse
width, duration, etc. (or change in polarity) can allow a
concomitant decrease or increase in the duration of the
stimulation.
[0101] In some embodiments, an implantable stimulator also can be
operated in a first mode which attempts to maintain airway patency
(and is therefore prophylactic) or a second mode, which recovers
airway patency that has been lost. In the first mode, a stimulation
pattern is applied that uses the minimum amount of stimulation
required to maintain airway patency, and may include (but is not
limited to) one of the stimulation patterns previously described
and illustrated in association with FIGS. 1-11. However, in the
event that an apnea occurred despite the attempt by the first mode
to prevent conditions leading to apnea, the implantable stimulator
would switch to a second, "acute" mode of operation, in which the
stimulation pattern would become more aggressive in amplitude,
frequency, pulse width, and duration of each stimulation burst. The
selected duration, amplitude, and frequency would be based on a
pre-obstruction respiratory rate. In one embodiment, managing the
switch between the first mode and the second mode, as well as
managing the stimulation parameters in the second mode, is
performed using substantially the same systems and methods, as
described in as described and illustrated in PCT Publication
WO/2010/059839, entitled A METHOD OF TREATING SLEEP APNEA,
published on May 27, 2010, and which is hereby incorporated by
reference.
[0102] In some embodiments, a flow limitation in the upper airway
is detected via respiratory sensors and/or pressure sensors to
determine a relative degree of obstruction. These sensors also can
be used to determine whether the obstruction is occurring during
inspiration, during expiration, or during both. Moreover, because
each type of obstruction yields a pressure/impedance pattern that
is characteristic of the particular type of obstruction, one can
use this sensing information to determine an efficacious
stimulation pattern.
[0103] In some embodiments, a stimulation pattern mimics the
pattern of the particular breathing phase. As shown in FIG. 12, a
respiratory cycle 653 includes an inspiratory phase 651 and an
expiratory phase 661. The inspiratory phase 651 includes an initial
portion 654, an intermediate portion 655, and an end portion 656
while the expiratory phase 661 includes an initial portion 664,
intermediate portion 665, peak 667, and end portion 676. As further
shown in the diagram 650 of FIG. 12, stimulation patterns 680 and
690 are applied, in which the greatest volume of stimulation
corresponds to ensuring airway patency during the greatest volume
of air flow during inspiration and expiration. Accordingly, in one
stimulation pattern 680 applied during the inspiratory phase 651,
the amplitude of stimulation ramps up through the progression of
the inspiratory phase 651. In particular, stimulation pattern 680
includes a start point 681, ramp portion 683, plateau portion 684,
descent 685, and end portion 682. In general terms, this ramped
stimulation pattern increases the stimulation amplitude (via ramp
portion 683) as inspiration commences and then maintains heightened
stimulation amplitude (via plateau portion 684) throughout most of
the second half of the inspiratory phase 651. While the plateau
portion 684 ends prior to completion of the inspiratory phase 651
in the example shown in FIG. 12, it will be understood that the
plateau portion 684 could be extended to last through the
completion of the inspiratory phase 651.
[0104] Meanwhile, in some embodiments, a ramped stimulation pattern
690 is applied to the expiratory phase 661 as further shown in FIG.
12. The stimulation pattern 690 includes a start point 691, plateau
portion 693, ramp portion 694, and end portion 692. In general
terms, this ramped stimulation pattern begins with a heightened
stimulation amplitude (via plateau portion 693) as inspiration
commences and then decreases the stimulation amplitude (via ramp
portion 694) throughout most of the second half of the expiratory
phase 651. In this stimulation pattern 690, a greater stimulation
is applied and maintained via plateau portion 693 at (and
immediately following) peak expiration 667 in order to ensure
airway patency at the beginning of the expiratory phase 661,
thereby proactively preventing airway collapse. Once expiration has
commenced, then the stimulation is decreased via ramp portion 694,
as the volume of air from expiration acts to help maintain airway
patency, with the stimulation pattern 690 terminating before the
end portion 676 of the expiratory phase 661.
[0105] FIG. 13 includes a diagram 700 schematically illustrating a
stimulation pattern 730, 740, according to one embodiment of the
present disclosure. As shown in FIG. 13, a respiratory cycle 703
includes an inspiratory phase 701 and an expiratory phase 711. The
inspiratory phase 701 includes an initial portion 704, an
intermediate portion 705, and an end portion 706 while the
expiratory phase 711 includes an initial portion 716, intermediate
portion 715, peak 717, and end portion 716. As further shown in
FIG. 13, the stimulation pattern 730 in the inspiratory phase 701
includes a first portion 733 of bursts 734 of stimulation in the
first half of the inspiratory phase 701 and then a generally
continuous stimulation segment 735 throughout the second half of
the inspiratory phase 701. Meanwhile, the stimulation pattern 740
in the expiratory phase 711 includes a first generally continuous
stimulation segment 743 through the first half of the expiratory
phase 711 and then a second portion 744 of bursts 745 of
stimulation in the second half of the expiratory phase 711. It will
be understood that in some embodiments, the stimulation segment 735
and the stimulation segment 743 form a substantially continuous
single stimulation segment, but are shown separately in FIG. 13 for
illustrative purposes.
[0106] In this embodiment, stimulation is applied in bursts 734 in
the early portion of the inspiratory phase 701 to maintain tone of
the upper airway and then continuous stimulation 735 is applied
during the latter half of the inspiratory phase 701 when maximum
air flow would occur and just prior to expiration when the airway
could be at greater risk for collapse. On the other hand, in the
expiratory phase 711, continuous stimulation 743 is applied during
the first half of the expiratory phase when there is a greater risk
of airway collapse (and maximum air flow needs to take place) while
bursts 745 of stimulation are applied during the second half of the
expiratory phase 711 to maintain tone and nominal airway
patency.
[0107] Although specific embodiments have been illustrated and
described herein, it will be appreciated by those of ordinary skill
in the art that a variety of alternate and/or equivalent
implementations may be substituted for the specific embodiments
shown and described without departing from the scope of the present
disclosure. This application is intended to cover any adaptations
or variations of the specific embodiments discussed herein.
Therefore, it is intended that this present disclosure be limited
only by the claims and the equivalents thereof.
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