U.S. patent application number 10/966484 was filed with the patent office on 2005-04-21 for system and method for mapping diaphragm electrode sites.
Invention is credited to Lee, Chang, Ligon, David, Meltzer, Mark, Mo, Anthony, Tehrani, Amir J..
Application Number | 20050085869 10/966484 |
Document ID | / |
Family ID | 34465515 |
Filed Date | 2005-04-21 |
United States Patent
Application |
20050085869 |
Kind Code |
A1 |
Tehrani, Amir J. ; et
al. |
April 21, 2005 |
System and method for mapping diaphragm electrode sites
Abstract
A signal source coupled to one or more electrodes in the
vicinity of the diaphragm for mapping therapeutic electrode sites.
A stimulus signal from the signal source may be applied to the one
or more electrodes to produce activation of the diaphragm.
Activation of the diaphragm is sensed to provide information that
may be correlated with the stimulus signal. The correlated
information may be used to identify a therapeutic locus for a
therapeutic electrode. An electrical stimulus comprising a series
of pulses may be applied to the one or more electrodes to elicit a
desired breathing response. The electrical stimulus may be applied
between intrinsic breathing cycles, or between regulated breathing
cycles. More than one electrode may be supported on a single
substrate. The substrate may configured to be positioned on the
diaphragm. A hierarchy of stimuli may be applied to a set of
electrodes.
Inventors: |
Tehrani, Amir J.; (Redwood
City, CA) ; Lee, Chang; (Redwood City, CA) ;
Ligon, David; (Redwood City, CA) ; Meltzer, Mark;
(Redwood City, CA) ; Mo, Anthony; (Redwood City,
CA) |
Correspondence
Address: |
PETERS VERNY JONES & SCHMITT, L.L.P.
425 SHERMAN AVENUE
SUITE 230
PALO ALTO
CA
94306
US
|
Family ID: |
34465515 |
Appl. No.: |
10/966484 |
Filed: |
October 15, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10966484 |
Oct 15, 2004 |
|
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10686891 |
Oct 15, 2003 |
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Current U.S.
Class: |
607/42 ;
600/529 |
Current CPC
Class: |
A61N 1/3601 20130101;
A61B 5/7264 20130101; A61B 5/08 20130101; A61B 5/4818 20130101;
A61N 1/36132 20130101; A61B 5/389 20210101 |
Class at
Publication: |
607/042 ;
600/529 |
International
Class: |
A61N 001/18 |
Claims
What is claimed:
1. A system for mapping therapeutic electrode sites on a diaphragm
comprising: a signal source configured to provide a stimulus for
eliciting a respiration response comprising an inspiration waveform
having a morphology; one or more implanted electrodes coupled to
the signal source and configured to deliver the stimulus to body
tissue within the body. a sensor configured to sense a parameter
corresponding to the respiration response; and, a processor coupled
to the sensor, configured to receive a signal from the sensor
corresponding to the respiration response, and configured to
determine a correlation between the morphology and a desired
morphology.
2. The system for mapping therapeutic electrode sites of claim 1
wherein the desired morphology comprises a natural breathing
pattern.
3. The system for mapping therapeutic electrode sites of claim 1
wherein the desired morphology is configured to elicit a desired
physiological response.
4. The system for mapping therapeutic electrodes sites of claim 3
wherein the desired physiological response is to influence SaO2
levels.
5. The system for mapping therapeutic electrodes sites of claim 3
wherein the desired physiological response is to influence PCO2
levels.
6. The system for mapping therapeutic electrode sites on a
diaphragm of claim 1 wherein the electrodes are coupled to a
substrate.
7. The system for mapping therapeutic electrode sites on a
diaphragm of claim 6 wherein the sensor is coupled to the
substrate.
8. The system for mapping therapeutic electrode sites on a
diaphragm of claim 1 wherein the waveform comprises information
representative of inter-abdominal pressure over time.
9. The system for mapping therapeutic electrode sites on a
diaphragm of claim 1 wherein the waveform comprises information
representative of thoracic pressure over time.
10. The system for mapping therapeutic electrode sites on a
diaphragm of claim 1 wherein the waveform comprises information
representative of movement of the diaphragm over time.
11. The system for mapping therapeutic electrode sites on a
diaphragm of claim 1 wherein the waveform comprises information
representative of at least a portion of a diaphragm EMG over
time.
12. The system for mapping therapeutic electrode sites on a
diaphragm of claim 1 wherein the waveform comprises information
representative of airway flow over time.
13. A system for mapping therapeutic electrode sites on a diaphragm
comprising: a signal source configured to provide a stimulus
configured to elicit a respiration response; one or more electrodes
coupled to the signal source and configured to deliver the stimulus
to tissue of a body; a sensor configured to sense a response to the
stimulus wherein the sensor is configured to sense at least one
parameter corresponding the respiration response; and, a processor
coupled to the sensor and configured to receive a signal
corresponding to the at least one parameter, wherein the processor
is configured to determine from the at least one parameter, a ratio
of a portion of peak volume over a portion of stimulation time.
14. The system of claim 13 wherein the processor is configured to
determine whether the percentage of peak volume per percentage of
and inspiration cycle corresponds to an acceptable respiration
response.
15. The system of claim 14 wherein the acceptable response is a
ratio of less than or equal to about 10.
16. The system of claim 15 wherein the acceptable response is a
ratio of less than or equal to about 3.5.
17. A system for mapping therapeutic electrode sites on a diaphragm
comprising: a signal source configured to provide a stimulus
configured to elicit a respiration response; one or more electrodes
coupled to the signal source and configured to deliver the stimulus
to tissue of a body; a sensor configured to sense a response to the
stimulus wherein the sensor is configured to sense at least one
parameter corresponding the respiration response; and, a processor
coupled to the sensor and configured to receive a signal
corresponding to the at least one parameter, wherein the processor
is configured to determine from the at least one parameter whether
a sustained inspiration portion of a stimulation duration for a
cycle is at an acceptable level.
18. The system of claim 17 wherein an acceptable level is about 0.5
of the stimulation duration or more.
19. The system of claim 17 wherein an acceptable level is about
0.75 of the stimulation duration or more.
20. A system for mapping therapeutic electrode sites on a diaphragm
comprising: a signal source configured to provide a stimulus
configured to elicit a respiration response; one or more electrodes
coupled to the signal source and configured to deliver the stimulus
to tissue of a body; a sensor configured to sense a response to the
stimulus wherein the sensor is configured to sense at least one
parameter corresponding the respiration response; and, a processor
coupled to the sensor and configured to receive a signal
corresponding to the at least one parameter, wherein the processor
is configured to determine from the at least one parameter whether
an instantaneous slope of peak flow over stimulation time is at an
acceptable level.
21. The system of claim 20 wherein an acceptable level of
instantaneous slope of peak flow over stimulation time is about 2
or less.
22. The system of claim 20 wherein an acceptable level of the
instantaneous slope of peak flow over stimulation time is about
0.75 or less.
23. A system for mapping therapeutic electrode sites on a diaphragm
comprising: a signal source configured to provide a stimulus
configured to elicit a respiration response; one or more electrodes
coupled to the signal source and configured to deliver the stimulus
to tissue of a body; a sensor configured to sense a response to the
stimulus wherein the sensor is configured to sense at least one
parameter corresponding the respiration response; and, a processor
coupled to the sensor and configured to receive a signal
corresponding to the at least one parameter, wherein the processor
is configured to determine from the at least one parameter whether
an instantaneous slope of peak flow over stimulation time is at an
acceptable level.
24. The system of claim 23 wherein an acceptable level of minimum
time to reach peak flow between about 100 milliseconds and 300
milliseconds.
25. The system of claim 23 wherein an acceptable level of minimum
time to reach peak flow is greater than or equal to about 300
milliseconds.
26. An electrode assembly comprising: an inflatable member
comprising a substrate and an inflation chamber configured to
receive an inflation medium; and one or more electrodes configured
to deliver or sense an electrical signal, coupled to the
substrate.
27. The electrode assembly of claim 26 wherein the assembly is
configured to be positioned on a diaphragm.
28. The electrode assembly of claim 26 further comprising a
manipulation member coupled to the inflatable member, wherein the
manipulation member is configured to position the inflatable member
in a desired location adjacent a portion of a body.
29. An electrode assembly for stimulating sites on a diaphragm
comprising: a member configured to be positioned on a diaphragm
during electrical stimulation of the diaphragm; and, a plurality of
electrodes coupled to the member and configured to deliver
electrical stimulation to the diaphragm.
30. The electrode assembly of claim 29 wherein the member comprises
a keyed portion configured to be positioned adjacent an anatomical
structure of the diaphragm to aid in positioning of the member.
31. The electrode assembly of claim 29 wherein the member comprises
a flexible portion configured to accommodate movement of the
diaphragm during electrical stimulation.
32. The electrode assembly of claim 29 wherein the member comprises
a perimeter having a shape that conforms to a specific feature on a
surface of a diaphragm.
33. The electrode assembly of claim 29 wherein the member comprises
an active surface configured to interface with a diaphragm surface,
wherein the plurality of electrodes is coupled to the active
surface of the member, and wherein the active surface is
curved.
34. The electrode assembly of claim 29 wherein at least one of the
plurality of electrodes comprises a subsurface electrode.
35. The electrode assembly of claim 29 wherein at least one of the
plurality of electrodes comprises a composite electrode.
36. The electrode assembly of claim 29 further comprising a
switching network coupled to the plurality of electrodes.
37. The electrode assembly of claim 29 wherein the member comprises
a mesh.
38. A method for delivering an electrode array to a diaphragm
comprising the steps of: providing an electrode array configured to
be compressed to a first configuration and to expand to a second
configuration; compressing the electrode array to the first
configuration; positioning the electrode array adjacent a diaphragm
within a subject's body; and expanding the electrode array to the
second configuration.
39. The method of claim 38 wherein the step of compressing the
electrode array comprises folding the electrode array; and wherein
the step of expanding the electrode array comprises unfolding the
electrode array.
40. The method of claim 38 wherein the step of expanding the
electrode array comprises inflating the electrode array.
40. A method for mapping electrode sites on a diaphragm, the method
comprising: placing a mapping electrode array on a surface of the
diaphragm; sensing and recording an intrinsic breathing pattern;
selecting an electrode of the mapping electrode array; delivering a
stimulus wave to the electrode; and, sensing and recording a
response to the stimulus wave.
41. The method of claim 40 further comprising calculating intrinsic
breathing parameters and establishing a target response.
42. The method of claim 41 further comprising comparing the
response to the target response.
43. The method of claim 42 further comprising the step of
determining whether the response sufficiently correlates with the
target response.
44. The method of claim 40 wherein the stimulus is applied
asynchronously.
45. The method of claim 40 wherein the stimulus is applied
synchronously.
46. The method of claim 40 wherein the stimulus is applied between
intrinsic breathing cycles.
47. A method for mapping electrode sites on a diaphragm, the method
comprising: placing a mapping electrode array on a surface of the
diaphragm; selecting an electrode of the mapping electrode array;
delivering a stimulus to the selected electrode; and, sensing and
recording a response to the stimulus.
48. The method of claim 47 further comprising the step of: defining
an acceptable breathing response morphology.
49. The method of claim 48 further comprising the step of comparing
the recorded response to the acceptable breathing response
morphology.
50. The method of claim 49 further comprising the step of
determining whether the response is sufficiently close to the
desired breathing response morphology.
51. A system for electrically stimulating a diaphragm comprising:
an implantable electrode configured to be positioned on the
diaphragm; a signal source configured to provide a stimulation
signal to the diaphragm through the electrodes, wherein the
stimulation signal comprises a series of pulses that vary in
amplitude.
52. The system of claim 51 wherein the pulses vary in
frequency.
53. A system for electrically stimulating a diaphragm comprising:
an implantable electrode configured to be positioned on the
diaphragm; a signal source configured to provide a stimulation
signal to the diaphragm through the electrodes, wherein the
stimulation signal comprises a series of pulses that vary in
frequency.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part to U.S. patent
application Ser. No. 10/686,891, "BREATHING DISORDER DETECTION AND
THERAPY DELIVERY DEVICE AND METHOD", by Tehrani filed Oct. 15,
2003, and incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to devices, systems, and
methods useful for determining locations for therapeutic electrode
placement on the diaphragm.
BACKGROUND
[0003] Electrical stimulation of the diaphragm has been performed
by delivering a stimulus to the diaphragm through one or more
electrodes. The location of the stimulation electrodes greatly
affects the ability to obtain a desired response with a given
stimulus and candidate electrode sites may be mapped in order to
aid in selecting a location for electrode placement.
[0004] Diaphragm mapping is the process of correlating electrical
stimuli applied at a set of points in the vicinity of the diaphragm
muscle with the associated responses of the diaphragm muscle. When
an electrical stimulus is applied, the diaphragm may respond
directly or indirectly.
[0005] In a direct response, the diaphragm is activated by a signal
that is received by muscle fibers without conduction along a nerve.
In an indirect response, the muscle fibers respond to a signal that
is conducted through a nerve. In general, activation of the
diaphragm muscle involves both direct and indirect responses. The
relative intensity of direct and indirect response will vary with
electrode location.
[0006] The threshold for action potential initiation of nerves and
muscle fibers is approximately the same. However, due to the signal
attenuation of muscle tissue, direct stimulation is more localized
with respect to an electrode than the response muscle tissue that
is stimulated through nerve recruitment. Thus, changes in electrode
location will typically affect the indirect and direct response
differently.
[0007] A motor point mapping system is described in "Laparoscopic
Placement of Electrodes for Diaphragm Pacing Using Stimulation to
Locate the Phrenic Nerve Motor Points," B. D. Schmit, T. A.
Stellato, M. E. Miller, and J. T. Mortimer, IEEE Trans. Rehab.
Eng., vol. 6, pp. 382-390, 1998. Mapping was done with the goal of
finding a functional motor point on the surface of the diaphragm at
which full hemidiaphragm activation could be achieved with a
minimum stimulus current. Full activation of the diaphragm was
correlated with a tidal volume or peak pressure value. Also, the
anatomical motor point was determined to be substantially in the
geometric center of a group of nerve branches.
[0008] Although electrode placement for obtaining full activation
may be achieved by mapping a motor point, there are situations in
which full activation may not be desirable, e.g., in the treatment
of sleep apnea, because it may disturb the sleep of the
subject.
[0009] U.S. Pat. No. 4,827,935 describes a demand electroventilator
using a plurality of electrodes adapted for placement on the skin.
It describes mapping locations on the skin for optimum electrode
location. It also uses the tidal volume to determine the optimal
placement. The optimum inspiratory points were located as the sites
where the maximum volume of air was inspired per milliampere of
current.
[0010] Since an activation level is characterized in each of these
references by a peak or integrated value, a given activation level
may be produced by many breathing patterns. Such peak or integrated
value is not believed to be sufficient to determine proper
placement of electrodes to achieve a desired breathing morphology
because placement of electrodes influences the coordinated
activation of various nerve and muscle fibers. Motor point mapping
as performed in the prior art, for example, does not provide the
information necessary for optimal placement of therapeutic
electrodes intended to stimulate breathing patterns similar to
those associated with certain activity levels such as, e.g., sleep.
Such natural breathing patterns may be characterized by pressure or
flow as a function of time. Also, tidal volume is not believed to
provide sufficient information for optimal placement of electrodes
to provide other desired inspiration morphologies that are
characterized by flow properties.
[0011] Additionally, known mapping techniques have been done where
the breathing of the subject is controlled by a ventilator, or by
inducing a particular state (e.g., apnea induced by
hyperventilation) and thus under artificial conditions. Threshold
and full activation mapping have been done under these conditions,
but it is not believed to be well suited for mapping that is
directed to identifying optimal electrode placement for replicating
intrinsic breathing patterns or for controlling or manipulating
specific aspects of breathing morphology and related
physiology.
[0012] Mapping has been done using a single electrode that is moved
from one location to the next, with stimuli being applied and
responses measured at each location. In this scheme there may be
some placement error when the mapping electrode is removed and
replaced with a permanent implanted electrode.
[0013] Thus, a need exists for a system and method of mapping sites
on the diaphragm for therapeutic electrode placement that is more
suitable to create intrinsic breathing or to control or manipulate
specific aspects of breathing morphology and related physiology. A
need also exists for a system and method that provides increased
accuracy of electrode placement.
BRIEF SUMMARY OF THE INVENTION
[0014] The present invention provides a signal source for eliciting
a desired respiration response that is coupled to one or more
electrodes in the vicinity of the diaphragm. A stimulus signal from
the source may be applied to the one or more electrodes to produce
activation of the diaphragm. Respiration response is sensed to
provide information that may be correlated with the stimulus
signal. The correlated information may be used to identify a
therapeutic locus for a therapeutic electrode.
[0015] Sensed respiration response may include, for example,
parameters indicating diaphragm activation such as diaphragm
movement or diaphragm EMG. Sensed respiration response may include
parameters such as flow, tidal volume, intraabdominal,
intrathoracic and airway pressure. Each of these parameters may be
observed over time where they create a respiration or inspiration
morphology.
[0016] In one embodiment of the invention an electrode is placed in
the vicinity of the diaphragm and an electrical stimulus is applied
between intrinsic breathing cycles, or regulated breathing
cycles.
[0017] In a further embodiment an electrical stimulus comprising a
series or burst of pulses is applied through one or more electrodes
to the diaphragm to elicit a natural breathing response. The series
of pulses may be varied in either or both amplitude and
frequency.
[0018] In another embodiment a support structure supporting one or
more electrodes is configured to be placed on the surface of the
diaphragm. The support structure may be, e.g., a mesh or other
flexible thin substrate. The support structure may comprise a
variety of materials such as, e.g., silicone, PTFE, polyurethane,
latex, polyester. The support structure may be a substrate with
electrodes positioned on, attached to, or formed with the
substrate. The substrate may be configured to be positioned on the
diaphragm, e.g., by aiding proper locating, positioning and
placement of the electrodes and/or by accommodating the movement of
the diaphragm. The substrate may also be shaped to fit on the
diaphragm and may also be keyed with anatomical structures to aid
in ideal positioning. Electrical stimuli are applied sequentially
and/or in combination through the electrodes to the diaphragm to
elicit a natural breathing response from the diaphragm.
[0019] Another feature provides an array of electrodes configured
to be laparoscopically delivered and to be positioned on the
diaphragm. In addition to features that allow the device to be
positioned on the diaphragm for stimulation, the substrate is
foldable, deflatable and/or contractible so that it can be
delivered through a small opening or cannula, and unfoldable,
inflatable or expandable to be positioned on the diaphragm.
[0020] In yet another embodiment a hierarchy of stimuli are applied
to a set of electrodes. At each level in the hierarchy the stimuli
are more complex with a greater number of adjustable parameters.
The set of electrodes may be reduced in number as each level in the
hierarchy is reached.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 shows a diagram of a system for mapping electrode
sites on a diaphragm in accordance with an embodiment of the
present invention.
[0022] FIG. 2A shows a guide grid on a diaphragm in accordance with
an embodiment of the present invention.
[0023] FIG. 2B shows electrode arrays placed with respect to an
anatomical feature in accordance with an embodiment of the present
invention.
[0024] FIG. 2C shows a template corresponding to each of electrode
arrays of FIG. 2B
[0025] FIG. 3A shows a top view of an array of electrodes on a
single substrate in accordance with an embodiment of the present
invention.
[0026] FIG. 3B shows a cross-section view of the electrode array of
FIG. 3A in accordance with an embodiment of the present
invention.
[0027] FIG. 4A shows an electrode array arranged on an inflatable
member in accordance with an embodiment of the present
invention.
[0028] FIG. 4B shows a diagram of an in situ electrode substrate in
accordance with an embodiment of the present invention.
[0029] FIG. 5 shows a perspective view of an electrode array with a
suction field surrounding the electrodes in accordance with an
embodiment of the present invention.
[0030] FIG. 6A shows a view of the active surface of an electrode
array with an inflatable member in accordance with an embodiment of
the present invention.
[0031] FIG. 6B shows a side view of the electrode array of FIG.
6A.
[0032] FIG. 6C shows the electrode array of FIG. 6A in a folded
configuration in accordance with an embodiment of the present
invention.
[0033] FIG. 7A shows a perspective view of an electrode array with
an inflatable member and suction field in accordance with an
embodiment of the present invention.
[0034] FIG. 7B shows a side view of the electrode array of FIG.
7A.
[0035] FIG. 7C shows the electrode array of FIG. 7A in a folded
configuration in accordance with an embodiment of the present
invention.
[0036] FIG. 8 shows a stimulus waveform in accordance with an
embodiment of the present invention.
[0037] FIG. 9A shows a natural breathing response waveform in
accordance with an embodiment of the present invention.
[0038] FIGS. 9B1-9B4 shows target, acceptable and unacceptable
breathing response waveforms in response to stimulation in
accordance with an embodiment of the present invention.
[0039] FIGS. 9C1-9C4 shows target, acceptable and unacceptable
breathing response waveforms in response to stimulation in
accordance with an embodiment of the present invention.
[0040] FIGS. 9D1-9D4 shows target, acceptable and unacceptable
breathing response waveforms in response to stimulation in
accordance with an embodiment of the present invention.
[0041] FIGS. 9E1-9E4 shows target, acceptable and unacceptable
breathing response waveforms in response to stimulation in
accordance with an embodiment of the present invention.
[0042] FIGS. 10A and 10B show timing diagrams for a stimulus
applied during intrinsic breathing in accordance with embodiments
of the present invention.
[0043] FIG. 11 shows an electrode array and sensors placed on the
diaphragm in accordance with an embodiment of the present
invention.
[0044] FIG. 12 shows a flow chart of a coarse mapping method in
accordance with an embodiment of the present invention.
[0045] FIG. 13A shows a flow chart of a method for intrinsic
breathing evaluation in accordance with an embodiment of the
present invention.
[0046] FIG. 13B shows a flow chart of a method for baseline
acquisition for mapping performed on a subject with regulated
breathing in accordance with an embodiment of the present
invention.
[0047] FIG. 14A shows a flow chart of a preliminary array mapping
method in accordance with an embodiment of the present
invention.
[0048] FIG. 14B shows a flow chart of a preliminary array mapping
method in accordance with an embodiment of the present
invention.
[0049] FIG. 15A shows a flow chart of a single parameter mapping
method in accordance with an embodiment of the present
invention.
[0050] FIG. 15B shows a flow chart of a single parameter mapping
method in accordance with an embodiment of the present
invention.
[0051] FIG. 16A shows a flow chart of a multi-parameter mapping
method in accordance with an embodiment of the present
invention.
[0052] FIG. 16B shows a flow chart of a multi-parameter mapping
method in accordance with an embodiment of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0053] FIG. 1 shows a system 100 for mapping electrode sites on a
diaphragm 155 of a subject 135. A laparoscopic imaging unit 130 is
coupled to a laparoscope 145 for observing the surface of the
diaphragm 155. The imaging unit 130 is coupled to a diaphragm
mapping control module 105. The imaging unit 130 may provide analog
or digital images to the control module 105. The control module 105
includes a monitor 110, processing unit 115 and an I/O module
120.
[0054] The monitor 110 may be used displaying a graphical user
interface and may also be used for displaying images. Displayed
images may be either real-time images from the imaging unit 130 or
stored images. Stored images may be overlaid with real-time images
to provide visual references for electrode placement.
[0055] The processing unit 115 includes a data processor, memory,
and program storage for data and image acquisition and
manipulation. The processing unit 115 is coupled to an input/output
(I/O) module 120, and may be used to control the timing of stimuli
delivered to mapping electrodes.
[0056] The I/O module 120 is coupled to the imaging unit 130, and
to one or more electrodes 151 on the mapping electrode substrate
150. The electrodes 151 on the mapping electrode substrate are
configured for electrical stimulation and/or sensing of the
diaphragm. The I/O module may also be coupled to other sensing
devices coupled to the subject 135, such as a respiratory sensor
125 (e.g., pneumotachometer) or electrical/mechanical sensors 140
and/or 152. Sensor 152 is shown positioned for sensing abdominal
movement, whereas sensor 140 is positioned for sensing movement in
the thoracic region 160. Sensors 140, 152 may also be used to sense
movement of the subject which can provide information, such as,
activity level of the subject. Alternatively other sensors may
positioned or coupled to the body and in communication with the I/O
module. The I/O module may also have a keyboard, mouse, or other
device for operator input.
[0057] Respiratory sensor 125 may be, e.g., a flow meter,
pneumotachometer, or pressure sensor used to measure tidal volume,
respiratory flow, and/or respiratory pressure. Sensor 140 may be,
e.g., a piezo-film sensor, multi-axis accelerometer, strain gauge,
pressure sensor, and may be used to measure abdominal movement,
diaphragmatic movement, other subject movement or activity,
intrathoracic pressure, or intraabdominal pressure.
[0058] The system 100 may be used to develop a coordinate system on
a per subject basis by capturing an image of the surface of the
diaphragm 155, upon which the mapping electrode substrate 150 is
attached. The image obtained by the imaging unit 130 is transferred
to the control module 105. Each time the mapping electrode
substrate 150 is moved, a new coordinate system is created. Once a
desired therapeutic locus is determined on the surface of the
diaphragm 155 as described in more detail below, the control unit
may use the images acquired during the mapping process to provide
guidance for placement of a permanent electrode, e.g. through
real-time visual aid (video feed, laser grid), audible proximity
indicator beeps, or haptic feedback.
[0059] FIG. 2A shows an abdominal view of a diaphragm 205 with a
reference grid 210 applied to the right hemidiaphragm 215 and a
reference grid 220 applied to the left hemidiaphragm 225. The
reference grid may be applied with an ink or dye, or it may be an
optical projection. The grids 210 and 220 may be used as a
reference for electrode placement.
[0060] FIG. 2B shows an abdominal view of a diaphragm 205 with
attached electrode substrates 230 and 235. The electrode substrates
are configured to be positioned on the diaphragm. The electrode
substrates 230, 235 include electrodes 233 located on the
substrates in a predetermined configuration. Electrode substrate
230 has a keyed or curved portion 231 on its perimeter that matches
the depression 245 on the central tendon 240. Similarly, electrode
substrate 235 has a keyed or curved portion 232 on its perimeter
that matches the depression 250 on the central tendon 240. The
keyed configuration of the electrode substrate 235 allows a more
precise locating, positioning and placement of the substrates on
the diaphragm. The substrates 230, 235 further include template
openings 234 for marking the position of the substrates 230, 235
after electrode selection has been made.
[0061] The electrode substrates 230 and 235 may be attached to the
diaphragm 205 in a number of ways with laparoscopic instruments,
for example with sutures, staples or clips, temporary adhesive
(bio-adhesive), and suction.
[0062] To identify the precise location of the selected mapping
electrode after the substrates 230, 235 have been removed, a mark
is made through each of the template openings 234. A template 236
as illustrated in FIG. 2C includes matching template openings 237
that match the orientation of the template openings 234 of the
substrates 230, 235. Electrode openings 238 in the template 236
also match the orientation of the electrodes 233 on the substrates
230, 235. Thus, using the marks made through template openings 234
in the substrates 230, 235, the template is positioned with
openings 237 over the marks. The electrode opening that corresponds
to the selected electrode on the array may then be used to mark the
correct location for a subsequently implanted electrode.
Permanently implanted electrodes may then be placed in position of
the selected optimal mapping electrode or electrodes as they were
positioned with the mapping substrate.
[0063] The electrode substrate may also include an adhesive dye
(which can be radio-opaque) in a pattern where once the substrate
is removed, the adhesive sticks to the diaphragm indicating key
locations so that mapped positions may be visually or
radiographically identified. The locations of the mapping substrate
and electrodes may also be identified with a photo taken of the
substrate in position on the diaphragm.
[0064] This and other electrode assemblies and/or substrates
described herein may be temporarily implanted or permanently
implanted and used for stimulation once the assembly or substrate
has been optimally positioned.
[0065] FIG. 3A shows a top view of an array of electrodes (310,315)
on a single substrate 305 in accordance with an embodiment of the
present invention. Electrode 310 is a subsurface electrode that is
intended to penetrate the peritoneum on the diaphragm, whereas
electrode 315 is a surface electrode that is intended for contact
with the surface of the peritoneum on the diaphragm. A subsurface
electrode 310 will generally provide a greater electrical
efficiency, whereas a surface electrode 315 will more easily couple
to a larger region. A surface electrode may 315 be combined with a
subsurface electrode 310 to form a single composite electrode.
These electrodes may also be selected to elicit a desired observed
response.
[0066] The substrate 305 is preferably fabricated from a flexible
material such as silicone, and may or may not be reinforced (e.g.,
with a mesh). The substrate is configured to fit on the diaphragm.
The perimeter of the substrate 305 may be round, elliptical, or a
more complex shape that conforms to a specific feature on the
diaphragm surface. A complex perimeter shape may be used to
facilitate placement of the substrate 305 at a particular location
on the surface of the diaphragm, such as one of the depressions
separating the three leaflets of the diaphragm, or characteristics
of the central tendon.
[0067] The electrode array on the substrate 305 may contain only
surface or subsurface electrodes or a combination of surface and
subsurface electrodes. The electrodes may be arranged in a regular
array using polar or rectangular coordinates, or they may be
arranged as an irregularly spaced array, e.g., that is correlated
with nerve structure that innervates the diaphragm. The electrodes
may be attached to the substrate a number of ways, e.g., glued,
welded, etched on, or encased with the substrate material.
[0068] FIG. 3B shows a cross-section view A-A of the electrode
array of FIG. 3A. The substrate is thicker in the central region
and tapers at the perimeter. A reinforcement 325 is also shown. The
taper at the perimeter 321 reduces the dynamic interfacial forces
that are produced between substrate and diaphragm during activation
of the diaphragm. The enhanced peripheral flexibility reduces
mechanical loading of the diaphragm and reduces the stress on the
attachment (e.g., sutures or suction). The substrate surface 320
upon which the electrodes reside may be flat, or it may be curved
to accommodate the surface of the diaphragm.
[0069] Electrodes 310 and 315 may be used individually as monopolar
electrodes for sensing and/or stimulation, or any two electrodes
may be select as a pair for bipolar sensing and/or stimulation.
[0070] The electrode assembly may also be in the form of a flexible
wire member such as a flexible loop. The flexibility of the loops
permits the ability to form the loops in the shape most ideally
suited for a particular patient. Other shapes may be used as well,
e.g. a loop with a branch that extends to the region adjacent the
anterior branches of the phrenic nerve. The control unit may be
programmed to activate the electrodes in a sequence that is
determined to elicit the desired response from the diaphragm.
[0071] The electrodes of the electrode assemblies once implanted,
may be selected to form bipolar or multipolar electrode pairs or
groups that optimize the stimulation response.
[0072] FIG. 4A shows an electrode array 400 coupled to an
inflatable member 405 defining an inflation chamber 406. In this
embodiment, the inflatable member 405 may be inflated to contact a
surface opposite the diaphragm to provide the force necessary to
hold the electrode array 400 against the surface of the diaphragm.
The electrodes may be coupled to an external I/O device with lead
wires extending inside of, outside of or within the walls of the
inflation tube. The inflation chamber 406 is coupled to a tube 420
that delivers an inflation medium to or from the chamber 407. The
tube 420 may also serve to couple the pressure within the inflation
chamber 407 to an external pressure transducer. Alternatively
pressure within the inflation chamber 407 may be sensed by a local
pressure transducer 425 which is coupled to an I/O port with a lead
or in a similar manner as the electrodes. The inflation chamber 407
may be evacuated in order to reduce the volume of the inflation
member 405 and electrode array 400 during an insertion or removal
procedure.
[0073] FIG. 4B shows a diagram of an in situ electrode substrate
406. In this example, the electrode substrate 406 is coupled to a
flexible tube 435 that penetrates the abdominal wall 440. A
switching network 450 couples lines 441 and 442 from the control
unit 430 to an array of nine electrodes. The switching network 450
allows any one or two of the nine electrodes to be selected, and
reduces the number of leads that must be connected directly to the
control unit 430. Electrode selection may be done either for
monopolar/bipolar sensing, or stimulus delivery.
[0074] The electrode substrate 406 may support one or more sensors
445 for sensing electrical or mechanical activity of the diaphragm.
Sensor 445 is coupled to the control unit 430 by lead 443. Examples
of electrical sensors are monopolar and bipolar electrodes for
electromyogram (EMG) sensing. Examples of mechanical activity
sensors are: strain gauges, pressure sensors, piezo-electric
devices, accelerometers, and position sensors.
[0075] FIG. 5 shows a perspective view of an electrode array
structure 505 with a suction field surrounding the electrodes 515
in accordance with an embodiment of the present invention. The
electrodes 515 are supported on a mesh 510 that is
circumferentially enclosed by a seal surface 520 that interfaces
with the diaphragm surface. A port 525 is used to connect a vacuum
source to the electrode array structure 505. Vacuum is applied
after the seal surface is placed on or mated to the surface of the
diaphragm.
[0076] FIG. 6A shows a view of the active surface of an electrode
array structure 605 with an inflation member 620 having an
inflation chamber 621 in accordance with an embodiment of the
present invention. Individual suction cups 615 are used to provide
the attaching force to the diaphragm. Electrodes 610 are
distributed on the surface between the suction cups 615. FIG. 6B
shows a side view 601 of the electrode array structure of FIG. 6A.
Vacuum ports 625 are shown connected to the suction cups 615, and a
fill/evacuation port 630 is shown coupled to the inflation chamber
621.
[0077] FIG. 6C shows the electrode array of FIG. 6A in a folded
configuration that is produced in conjunction with deflation of the
inflation member 620. The deflation of the inflation chamber 621 of
the inflation member 620 produces a reduction in volume and an
elongated shape that facilitates the introduction and removal of
the electrode array structure 605 through a cannula or a narrow
opening.
[0078] FIG. 7A shows a perspective view of an electrode array 705
on an inflation member 740 with an inflation chamber 741 and a
suction field mesh 710 in accordance with an embodiment of the
present invention. Electrodes 715 are supported on the mesh 710.
The mesh 710 is surrounded by a seal surface 720. The inflation
chamber 741 is coupled to a fill/evacuation port 730. An evacuation
port 725 is used provide to provide vacuum to the electrode array
705. Having the mesh 710 with electrodes 715 inside the suction
field allows stabilization of the tissue via vacuum and provides
intimate contact between the tissue and the electrodes 715 during
contraction of the diaphragm. FIG. 7B shows a side view of the
electrode array of FIG. 7A. The inflation member 740 has a radial
symmetry (e.g., toroidal) with respect to the evacuation port
725.
[0079] FIG. 7C shows the electrode array of FIG. 7A in a folded
configuration that is produced in conjunction with deflation of the
inflation member 740. The deflation of the inflation member 740
produces a reduction in volume and an elongated shape that
facilitates the introduction and removal of the electrode array
structure 705 through a cannula or a narrow opening.
[0080] The electrode arrays described herein may be configured to
be laparoscopically delivered to the diaphragm. They may be
compressed to a smaller configuration and then expanded to be
positioned on the diaphragm. They may also be delivered as
individual components and assembled at the diaphragm. They may also
be delivered as individual components and assembled at the
diaphragm.
[0081] FIG. 8 shows an example of a stimulus waveform 800 that may
be applied to the diaphragm through an electrode. Waveform 800 is a
biphasic pulse train; however, in other embodiments a monophasic or
other multiphasic pulse train may be used. The individual pulses
within the pulse train 800 may have variable amplitudes. For
example, pulse 805 has an amplitude A.sub.1 that is smaller than
the amplitude A.sub.2 of pulse 810. The pulse train 800 may also
have a variable frequency, with the period P.sub.1 between pulses
813 and 815 being greater than the period P.sub.2 between
succeeding pulses 820 and 825. The first pulse amplitude A.sub.1
may be selected to on the basis of an observed or measured
threshold value associated with the response of the diaphragm to an
applied stimulus (e.g., an observed muscle twitch).
[0082] The stimulus waveform or pulse train 800 may incorporate a
delay D between positive and negative pulses, as shown between
positive pulse 810 and negative pulse 811.
[0083] FIG. 9A shows an example of a natural breathing flow
response waveform 905 associated with a stimulation waveform 910
delivered to a therapeutic locus on the diaphragm. For purposes of
this disclosure, "intrinsic breathing" refers to breathing that is
not induced by an applied stimulus, and "natural breathing" refers
to breathing that is similar or identical to intrinsic breathing,
but is induced by an applied stimulus. The natural breathing flow
response waveform 905 is similar to intrinsic respiration waveforms
observed in humans. Flow increases gradually during most of the
inspiration phase to a peak value, followed by a relatively sharp
decline in flow to the onset of the expiration phase. In this
example, the first pulse in the stimulation waveform 910 has an
amplitude A.sub.t, that is equal to a measured or observed
threshold value for the therapeutic locus. FIG. 9A similarly
illustrates a natural breathing EMG response waveform 906 and
envelope 907 associated with the stimulation waveform 910.
[0084] FIG. 9B1 illustrates a stimulation waveform 925 delivered to
candidate therapeutic loci on the diaphragm. The various loci of
stimulation correspond to resulting response waveforms 926, 927,
928 illustrated in FIGS. 9B2, 9B3, 9B4 respectively and each
corresponding to a response resulting from stimulation at a
different locus. Different waveforms may also result from
variations in the stimulation pulses such as, e.g., in frequency
pulse duration and amplitudes as well as by using different
electrode firing sequences as described for example in parent
application Ser. No. 10/686,891.
[0085] The waveform responses illustrated in FIGS. 9B1-9B2 are
measured in airflow but may also be determined, from other
respiration parameters, e.g. EMG or diaphragm movement.
"Morphology" refers to the shape or form of the respiration
waveform or waveform envelope and may include various aspects of
the waveform including, e.g., length of various portions of the
waveform, amplitude, frequency or slope. A desired response may be
natural breathing as illustrated in FIG. 9A or another desired
response.
[0086] FIG. 9B2 illustrates a waveform response 926 in an ideal,
preferred or target range. According to this target morphology, for
a given portion of the inspiration cycle positive inhalation is
sustained. A sustained inhalation period or portion of time is an
inhalation period in which there is a positive airflow. The target
range may be expressed as a portion, fraction or percentage of time
of the inspiration cycle in which there is a positive or sustained
inhalation. While this effect may be expressed in these terms, a
percentage or fraction calculation is not required to achieve the
effect of the invention or its equivalent. The target range is from
about 75% to 100% sustained inhalation. The waveform illustrated in
FIG. 9B2 shows an inspiration cycle where 95% or 0.95 of the
inspiration cycle is sustained positive inhalation.
[0087] FIG. 9B3 illustrates a waveform response 927 in an
acceptable range. The acceptable range is between about 50% and
100% sustained inhalation. The illustrated waveform is at 60%
sustained positive inhalation.
[0088] FIG. 9B4 illustrates a waveform 928 response in an
unacceptable range. The unacceptable range is below about 50%
sustained inhalation. The illustrated waveform is at 20% sustained
positive inhalation. Less than about 50% suggests poor efficiency
of the delivered stimulation pulse.
[0089] It is believed that long period of isometric diaphragm
contraction can lead to diaphragm fatigue and patient discomfort.
Staying within the target range suggests increased energy
efficiency, likely responses similar to physiologic or natural
conditions. Gradual contraction is also less likely to cause airway
collapse or stretch receptor inhibition reflex and is likely to
provide more comfortable breathing for patients.
[0090] FIG. 9C1 illustrates a stimulation waveform 935 delivered to
candidate therapeutic loci on the diaphragm. The various loci of
stimulation correspond to resulting response waveforms 936, 937,
938 illustrated in FIGS. 9C2, 9C3, 9C4 respectively and each
corresponding to a response resulting from stimulation at a
different locus (or alternatively by varying stimulation
parameters).
[0091] The waveform responses illustrated in FIGS. 9C1-9C2 are
measured in airflow but may also be determined, from other
respiration parameters, e.g. EMG or diaphragm movement.
[0092] FIG. 9C2 illustrates a waveform response 936 in an ideal,
preferred or target range. According to this target morphology, the
ratio of peak flow over stimulation time for a given portion of the
inspiration cycle is less than about 3.5. The ratio may also be
expressed as a ratio of percentage of peak flow over a percentage
of pacing time. While the effects herein may be expressed as a
certain value, a specific calculation of the value is not required
to achieve the invention or its equivalent.
[0093] FIG. 9C3 illustrates a waveform response 937 in an
acceptable range. The acceptable range ratio of peak flow over
pacing time is about less than or equal to about 10.
[0094] FIG. 9C4 illustrates a waveform response 938 in an
unacceptable range. The unacceptable range ratio of peak flow over
pacing time is above about 10. A ratio above 10 suggests an abrupt
flow which may cause airway collapse, stretch receptor inhibition
reflex, or pain for patients.
[0095] FIG. 9D1 illustrates a stimulation waveform 945 delivered to
candidate therapeutic loci on the diaphragm. The various loci of
stimulation correspond to resulting response waveforms 946, 947,
948 illustrated in FIGS. 9D2, 9D3, 9D4 respectively and each
corresponding to a response resulting from stimulation at a
different locus (or alternatively by varying stimulation
parameters).
[0096] The waveform responses illustrated in FIGS. 9D1-9D2 are
measured in airflow but may also be determined, from other
respiration parameters, e.g. EMG or diaphragm movement.
[0097] FIG. 9D2 illustrates a waveform response 946 in an ideal,
preferred or target range. According to this target morphology, the
instantaneous slope of peak flow over stimulation time for a given
portion of the inspiration cycle is less than about 0.75. The ratio
may also be expressed as a ratio of percentage of peak flow per
milliseconds. While the effects herein may be expressed as a
certain value, a specific calculation of the value is not required
to achieve the invention or its equivalent.
[0098] FIG. 9D3 illustrates a waveform response 947 in an
acceptable range. The acceptable range of instantaneous peak flow
over time is about less than or equal to about 2.
[0099] FIG. 9D4 illustrates a waveform response 948 in an
unacceptable range. The unacceptable range of instantaneous peak
flow over time is above about 2. A ratio above 2 suggests an abrupt
flow which may cause airway collapse, stretch receptor inhibition
reflex, or pain for patients.
[0100] FIG. 9E1 illustrates a stimulation waveform 955 delivered to
candidate therapeutic loci on the diaphragm. The various loci of
stimulation correspond to resulting response waveforms 956, 957,
958 illustrated in FIGS. 9E2, 9E3, 9E4 respectively and each
corresponding to a response resulting from stimulation at a
different locus (or alternatively by varying stimulation
parameters).
[0101] The waveform responses illustrated in FIGS. 9E1-9E2 are
measured in airflow but may also be determined, from other
respiration parameters, e.g. EMG or diaphragm movement.
[0102] FIG. 9E2 illustrates a waveform response 956 in an ideal,
preferred or target range. According to this target morphology, the
minimum time elapsed before peak flow is achieved is greater than
or equal to about 300 milliseconds or more.
[0103] FIG. 9E3 illustrates a waveform response 957 in an
acceptable range. The acceptable range of minimum time to reach
peak flow is greater than or equal to about 100 milliseconds and
more preferably between about 100 milliseconds and 300
milliseconds.
[0104] FIG. 9E4 illustrates a waveform response 958 in an
unacceptable range. The unacceptable range minimum time to reach
peak flow is less than about 100 milliseconds. A time below about
100 ms suggests an abrupt flow which may cause airway collapse,
stretch receptor inhibition reflex, or pain for patients.
[0105] Various desired responses may also include waveforms or
morphologies that have a desired physiological outcome or effect
such as desired blood oxygen saturation levels or PCO2 levels.
Minute ventilation may be increased or decreased with respect to a
baseline minute ventilation. This may be done by manipulation of
one or more parameters affecting minute ventilation. Some of the
parameters may include, for example, tidal volume, respiration
rate, flow morphology, flow rate, inspiration duration, slope of
the inspiration curve, and diaphragm created or intrathoracic
pressure gradients. Increasing minute ventilation generally
increases the partial pressure of O.sub.2 compared to a reference
minute ventilation. Decreasing minute ventilation generally
increases the partial pressure of CO.sub.2 compared to a reference
minute ventilation.
[0106] As noted variations in stimulation parameters may be used to
elicit different responses and therefore may also be used to
determine optimal electrode location as well as optimal stimulus
parameters. This stimulation may also be done with multiple
electrodes simultaneously or in a sequence.
[0107] The system may adjust the pace, pulse, frequency and
amplitude within a series of pulses to induce or control various
portions of a respiratory cycle, inspiration, exhalation, tidal
volume (area under waveform curve) slope of inspiration, fast
exhalation and other parameters of the respiratory cycle. The
system may also adjust the rate of the respiratory cycle.
[0108] The stimulation optimization may be used not only for
mapping to identify electrode sites but may also be used to
determine stimulation parameters for the ultimately implanted
device. As such the ideal, preferred, target and acceptable
waveform morphologies are not only for mapping but are also ideal,
preferred, target and acceptable stimulation responses in the
implanted device.
[0109] A breathing response depends upon both the electrode
location and the applied stimulus waveform. Not all electrode
locations may be capable of producing a desired response. Also,
different stimulus waveforms may be required at those locations
that are shown to be capable of producing a desired response.
[0110] FIG. 10A shows a timing diagram for a fixed stimulus 1000
applied during a rest period associated with intrinsic (or
regulated) breathing. Regulated breathing refers to a predominantly
regular breathing pattern that is produced by external assistance
(e.g., a ventilator). Fixed stimulation may also be done during
absence of breathing (e.g., in apnea) where stimulation is applied
a certain period of time after apnea has begun. The fixed stimulus
may be applied after a percentage (e.g., 30%) of the observed rest
period has elapsed, or it may be applied after a fixed period of
time has elapsed. The fixed period of time may be referenced to the
beginning of inhalation 1005, end of inhalation 1010, or end of
exhalation 1015. The fixed time period may also be referenced to a
period of time after EMG waveform 1006 has stopped or after the EMG
envelope 1007 has fallen off. Fixed stimulation is not necessarily
in phase with intrinsic respiration, and rather, is offset from a
previous cycle.
[0111] FIG. 10B shows a timing diagram for a dynamically
synchronized stimulus 1020 applied during a rest period associated
with intrinsic (or regulated) breathing. The dynamically
synchronized stimulus is applied after a delay equal to the length
of the inspiration phase, expiration phase, or the total
respiratory cycle. The delay is indexed to the end of the
respiration cycle 1035. In this example the delay at 1035 is
approximately equal to or less than the total respiratory cycle.
The delay may also be equal to the length of the EMG signal 1036 or
to the length of the EGM envelope 1037. The delay may also be
indexed to the end of the EMG envelope 1038. Dynamic
synchronization may occur or be adjusted breath to breath.
[0112] While the stimulation may be fixed or dynamically
synchronized, it may also switch between fixed and dynamically
synchronized, for example depending on the rate of respiration. If
a subject is hyperventilating, hypoventilating or apneaic, the
stimulation may revert to a fixed stimulation mode.
[0113] FIG. 11 shows an abdominal view of a diaphragm 1105 with
attached electrode substrates 1110 and 1120. Electrode substrates
1110, 1120 have keyed portions 1111, 1121 respectively for
positioning the substrate 1110, 1120 on a conforming portions or
surfaces of the central tendon 1106. Electrode substrate 1110
located on the right hemidiaphragm 1115 has a pair of extensions
1126a-b. Electrode substrate 1120 located on the left hemidiaphragm
1125 has a single extension 1126c. Each extension 1126a-c supports
a peripheral device 1130 that may be either an electrode (e.g.,
stimulation or sensing electrode) or a sensor (e.g., movement
sensor). The extensions 1126a-c are located adjacent specific
portions of the diaphragm apart from the stimulation electrodes.
The peripheral device or devices 1130 sense movement or EMG at a
distal or radial location from the stimulation electrodes on the
electrode substrates 1110, 1120. This sensed movement or EMG may be
used to confirm activation or degree of activation of the diaphragm
from stimulation by one or more electrodes on the substrates 1110,
1120.
[0114] FIGS. 12 through 16 show a series of flow charts for process
sequences that may be combined to provide a hierarchical method for
mapping diaphragm electrode sites. First, coarse mapping is done as
described with reference to FIG. 12. Coarse mapping entails testing
a wide area on the diaphragm which is typically greater than the
are of the electrode assembly used in testing. Once an area for
electrode array positioning is determined, specific electrode
position testing is performed and then stimulation optimization as
described in FIGS. 13A-16B. These process sequences may be
performed using all or part of the system shown in FIG. 1.
[0115] FIGS. 13A, 14A, 15A and 16A are directed to patients who are
breathing on their own. FIGS. 13B, 14B, 15B and 16B are directed to
patients in artificial respiratory states (i.e.--ventilator
dependent.
[0116] FIG. 12 shows a flow chart of a coarse mapping method in
accordance with an embodiment of the present invention. This method
may be used as a preliminary mapping process to determine the
initial placement of an electrode array. Coarse mapping may be
useful since physical land marks provided by the diaphragm might
not be enough to identify an optimal positioning of the electrode
array. In order to determine sections of the diaphragm that is more
responsive to electrical stimulation course mapping may be
performed. In step 1210 a coordinate system is established in a
selected area. The selected area is typically larger than the foot
print of the electrode array being placed. Selection of the area
may be based upon visually observable features of the diaphragm, or
may use information regarding the nerve structure of the diaphragm
obtained by computer aided tomography (CAT), or other imaging
technologies.
[0117] In step 1215 a single electrode probe is used to probe a
series of points distributed across the area selected in step 1210.
The locations may be marked, e.g. with ink, a laser grid, or on a
monitor. The system depicted in FIG. 1 may be used, with the single
electrode probe being substituted for the electrode substrate 150.
A fixed waveform may be applied at each location and a response
sensed, e.g., by one of the previously mentioned techniques.
[0118] In step 1220 the pattern of test locations obtained in step
1215 is evaluated to determine where within the selected area the
electrode array should be placed. For example, the electrode array
may be placed in the region of the selected area for which the
underlying test points have the highest average response value. At
step 1225 the process is done.
[0119] FIG. 13A shows a flow chart 1300 of a method for intrinsic
breathing evaluation in accordance with an embodiment of the
present invention. This process is typically used prior to applying
mapping stimuli in order to establish a target response that may be
subsequently updated during mapping.
[0120] In step 1310 the mapping electrode array is placed on the
diaphragm. The mapping electrode array may be placed using the
results of the coarse mapping procedure shown in FIG. 12, or may be
placed using physical features of the diaphragm.
[0121] In step 1315 the intrinsic breathing pattern is sensed and
recorded using respiratory flow sensors to determine time dependent
characteristics such as flow rate, pressure and tidal volume.
[0122] In step 1320 the intrinsic breathing diaphragm movement and
activity are sensed and recorded using electrical (e.g., EMG)
and/or mechanical (e.g., accelerometer or strain gauge)
sensors.
[0123] In step 1325 the intrinsic breathing parameters associated
with the observed intrinsic breathing pattern are calculated to
provide reference values for subsequent comparison to those
calculated from observed responses to mapping stimuli. Examples of
intrinsic (or desired) breathing parameters are inspiration length,
exhalation length, rate, amplitude, rest length and cycle length,
slope of the inspiration cycle, slope of the expiration cycle, peak
flow per time, percent peak flow per percent of inspiration time,
and sustaining positive flow as a time value or as a percent of
inspiration cycle.
[0124] In step 1330 the optimum stimulation timing is determined.
As previously discussed, the stimulation may be dynamically
synchronized or fixed. At step 1335 the process is done.
[0125] FIG. 13B shows a flow chart of a method for baseline
acquisition for mapping performed on a subject with regulated
breathing in accordance with an embodiment of the present
invention. Subjects with regulated breathing, such as those on a
ventilator may lack the diaphragm activity associated with
intrinsic breathing. In such cases, a baseline is developed during
monitored intrinsic breathing prior to regulation. The baseline
reference is a target response that is not updated during
mapping.
[0126] In step 1340 a respiratory flow monitor (e.g., a
pneumotachometer) is placed on the subject. In step 1345 the
intrinsic breathing pattern is recorded.
[0127] In step 1350 the intrinsic breathing parameters are
calculated. In contrast to the process of FIG. 13A, information
regarding diaphragm activity is not used.
[0128] In step 1355 the baseline reference is stored. Since
intrinsic breathing is absent during mapping performed on a subject
with regulated breathing, the baseline reference will not change
during mapping. At step 1360 the process is done.
[0129] FIG. 14A shows a flow chart of a preliminary array mapping
method for intrinsic breathing (or desired breathing) in accordance
with an embodiment of the present invention. In step 1410 an
electrode is selected from the array. In step 1415 a locator wave
is applied to the selected electrode (e.g., fixed or dynamically
synchronized). A locator wave typically has fixed parameters and a
low current and is a wave that will evoke an observable response
for area close to the desired permanent electrode implantation
site(or desired).
[0130] In step 1420 the response to the locator wave is sensed and
stored. A desired or acceptable response may be with respect to any
of the parameters set forth with respect to FIG. 13A. The response
may be a particular parameter such as, e.g., the amplitude of the
response.
[0131] In step 1425 the intrinsic breathing pattern is sensed and
recorded. In step 1430 the intrinsic breathing parameters are
recalculated. In step 1435 the stored response is compared to the
intrinsic breathing parameters, and an accuracy score or figure of
merit is determined for the response.
[0132] At step 1440 a check is made to see if all of the electrodes
in the array have been evaluated. If not, steps 1410 through 1435
are repeated. If all electrodes have been evaluated, the process is
done at step 1445.
[0133] FIG. 14B shows a flow chart of a preliminary array mapping
method for regulated breathing in accordance with an embodiment of
the present invention. In step 1450 an electrode is selected from
the array. In step 1455 a locator wave is applied to the selected
electrode (e.g., in a dynamic or fixed synchronized manner). A
locator wave typically has fixed parameters and a low current.
[0134] In step 1460 the response to the locator wave is sensed and
stored. In step 1465 the stored response is compared to a baseline
reference (e.g., as obtained from the process of FIG. 13B), and an
accuracy score or figure of merit is determined for the
response.
[0135] At step 1470 a check is made to see if all of the electrodes
in the array have been evaluated. If not, steps 1450 through 1465
are repeated. If all electrodes have been evaluated, the process is
done at step 1475.
[0136] FIG. 15A shows a flow chart of a single parameter mapping
method for intrinsic breathing in accordance with an embodiment of
the present invention. In step 1510 a set of candidate electrodes
is selected, i.e., electrodes that have given the best response.
This set may be selected on the basis of accuracy scores determined
by the process shown in FIG. 14A. In step 1515 a response parameter
is selected for qualification. Examples of response parameters are:
inspiration length, exhalation length, rate, amplitude, rest length
and cycle length, slope of the inspiration cycle, slope of the
expiration cycle, peak flow per time, percent peak flow per percent
of inspiration time, and sustaining positive flow as a time value
or as a percent of inspiration cycle.
[0137] In step 1520 a test wave is adjusted to match the intrinsic
breath duration. Other parameters may subsequently be adjusted, for
example: by lowering maximum current or lowering maximum frequency
if peak flow/movement/EMG/volume/etc. are achieved too quickly; by
increasing initial current amplitude or initial frequency if
flow/EMG/pressure/etc initiation is delayed from delivery of
initial pulse; or by changing (e.g., increasing) the ramp slope if
flow/movement/EMG/volume/etc. has had more than one peak during an
inspiration period. Other parameters that may also be adjusted are
amplitude, frequency, shape, and timing. The test wave may also be
adjusted to achieve a desired response, e.g., a percent of
sustained positive airflow with respect to an inspiration cycle or
other response.
[0138] In step 1525 an individual electrode is selected from the
set of candidate electrodes selected in step 1510. In step 1530 the
test wave constructed in step 1520 is delivered to the electrode
(e.g., fixed or dynamically synchronized). In step 1535 the
response to the test wave is sensed and stored.
[0139] In step 1540 the intrinsic breathing pattern is sensed and
recorded. In step 1545 the intrinsic breathing parameters are
recalculated. In step 1550 the stored response is compared to the
intrinsic breathing parameters, and an accuracy score or figure of
merit is determined for the response.
[0140] At step 1555 a check is made to see if all of the electrodes
in the array have been evaluated. If not, steps 1510 through 1550
are repeated. If all electrodes have been evaluated, the process is
done at step 1560.
[0141] FIG. 15B shows a flow chart of a single parameter mapping
method for regulated breathing in accordance with an embodiment of
the present invention. In step 1570 a set of candidate electrodes
is selected. This set may be selected on the basis of accuracy
scores determined by the process shown in FIG. 14B. In step 1572 a
response parameter is selected for qualification. Examples of
response parameters are: EMG, flow, tidal volume, movement and
pressure.
[0142] In step 1574 a test wave is adjusted to match the intrinsic
breath duration. Other parameters that may also be adjusted as
well. In step 1576 an individual electrode is selected from the set
of candidate electrodes selected in step 1570. In step 1578 the
test wave constructed in step 1574 is delivered to the electrode
(e.g., fixed or dynamically synchronized). In step 1580 the
response to the test wave is sensed and stored.
[0143] In step 1582 the stored response is compared to a baseline
reference, and an accuracy score or figure of merit is determined
for the response.
[0144] At step 1584 a check is made to see if all of the electrodes
in the array have been evaluated. If not, steps 1570 through 1582
are repeated. If all electrodes have been evaluated, the process is
done at step 1586.
[0145] FIG. 16A shows a flow chart of a multi-parameter mapping
method for intrinsic breathing in accordance with an embodiment of
the present invention. In step 1610 an electrode is selected. The
electrode may be selected on the basis of the accuracy score
determined in the process shown in FIG. 14A or FIG. 15A.
[0146] In step 1615 a plurality of response parameters are selected
for qualification. This may be done to refine the elelctorde choice
or if a single parameter has not resulted in an electrode
selection. Adjustments may be made where necessary in a manner
similar as described with reference to FIG. 15A. Examples of
response parameters are: EMG, flow, tidal volume, movement and
pressure. An example of a pair of parameters are tidal volume and
the measured parameter associated with diaphragm activation that
shows the greatest dynamic range.
[0147] In step 1620 a therapy wave is adjusted to match the
intrinsic breath duration. Other parameters may also be adjusted as
described with reference to FIG. 15A. For example, the therapy wave
may be adjusted to elicit an inspiration slope, a percentage peak
value in a minimum percentage of the inspiration cycle, or a
percentage of the peak inspiriaton in a minimum amount of time. In
step 1625 the therapy wave constructed in step 1620 is delivered to
the electrode (e.g., fixed or dynamically synchronized). In step
1630 the response to the therapy wave is sensed and stored.
[0148] In step 1635 the intrinsic breathing pattern is sensed and
recorded. In step 1640 the intrinsic breathing parameters are
recalculated. In step 1645 the stored response is compared to the
intrinsic breathing parameters, and an accuracy score or figure of
merit is determined for the response.
[0149] At step 1650 a check is made to see if the accuracy score or
figure of merit determined in step 1645 is greater than a
predetermined value. If not, steps 1610 through 1645 are repeated.
If yes, the electrode location is qualified as a therapeutic locus
and the process is done at step 1655.
[0150] FIG. 16B shows a flow chart of a multi-parameter mapping
method for regulated breathing in accordance with an embodiment of
the present invention. In step 1660 an electrode is selected. The
electrode may be selected on the basis of the accuracy score
determined in the process shown in FIG. 14B or FIG. 15B.
[0151] In step 1665 at least two response parameters are selected
for qualification. Examples of response parameters are: EMG, flow,
tidal volume, movement and pressure. An example of a pair of
parameters are tidal volume and the measured parameter associated
with diaphragm activation that shows the greatest dynamic
range.
[0152] In step 1670 a therapy wave is adjusted to match the
intrinsic breath duration. Other parameters may also be adjusted.
In step 1675 the therapy wave constructed in step 1670 is delivered
to the electrode (e.g., fixed or dynamically synchronized). In step
1680 the response to the therapy wave is sensed and stored.
[0153] In step 1685 the stored response is compared to a baseline
reference, and an accuracy score or figure of merit is determined
for the response.
[0154] At step 1690 a check is made to see if the accuracy score or
figure of merit determined in step 1685 is greater than a
predetermined value. If not, steps 1660 through 1685 are repeated.
If yes, the electrode location is qualified as a therapeutic locus
and the process is done at step 1695.
[0155] With respect to hierarchical optimization scheme described
with reference to FIGS. 13-16, if one parameter does not give the
user control over enough breathing parameters to match the
intrinsic breathing characteristics, then another parameter is
hierarchically added and adjusted that parameter until it provides
sufficient control. If it does not, then again, another parameter
is added until sufficient control over the breathing pattern or
morphology is reached.
[0156] As an alternative, instead of using a natural breathing
pattern as set for the with respect to FIGS. 12-16B, a desired
breathing pattern, for example, to manipulate physiological
responses or to treat disorders, may be selected or programmed into
the device. The electrodes may the be selected as set forth with
reference to FIGS. 14-16 using the desired breathing pattern
instead of the natural breathing pattern for comparison.
[0157] The stimulation device may be used, for example in subjects
with breathing disorders, heart failure patients and patients who
cannot otherwise breathe on their own such as spinal cord injury
patients.
[0158] Safety mechanisms may be incorporated into any stimulation
device in accordance with the invention. The safety feature
disables the device under certain conditions. Such safety features
may include a patient or provider operated switch, e.g. a magnetic
switch. In addition a safety mechanism may be included that
determines when patient intervention is being provided. For
example, the device will turn off if there is diaphragm movement
sensed without an EMG as the case would be where a ventilator is
being used.
[0159] While the invention has been described in detail with
reference to preferred embodiments thereof, it will be apparent to
one skilled in the art that various changes can be made, and
equivalents employed, without departing from the scope of the
invention.
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