Patent Application
20050085869
The present invention relates to devices, systems, and methods useful for determining locations for therapeutic electrode placement on the diaphragm.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
FIGS. 9B1-9B4 shows target, acceptable and unacceptable breathing response waveforms in response to stimulation in accordance with an embodiment of the present invention.
FIGS. 9C1-9C4 shows target, acceptable and unacceptable breathing response waveforms in response to stimulation in accordance with an embodiment of the present invention.
FIGS. 9D1-9D4 shows target, acceptable and unacceptable breathing response waveforms in response to stimulation in accordance with an embodiment of the present invention.
FIGS. 9E1-9E4 shows target, acceptable and unacceptable breathing response waveforms in response to stimulation in accordance with an embodiment of the present invention.
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.
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.
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.
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.
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.
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.
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
1 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.
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
2 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
3 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.
4 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.
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.
1 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).
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.
2 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.
3 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.
4 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.
1 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).
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.
2 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.
3 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.
4 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.
1 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).
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.
2 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.
3 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.
4 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.
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 O2 compared to a reference minute ventilation. Decreasing minute ventilation generally increases the partial pressure of CO2 compared to a reference minute ventilation.
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.
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.
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.
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.
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.
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
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.
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
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.
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.
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.
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.
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.
In step 1350 the intrinsic breathing parameters are calculated. In contrast to the process of
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.
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
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.
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.
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
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.
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.
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.
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.
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.
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.
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.
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.
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
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
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.
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.
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.
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.
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.
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.
With respect to hierarchical optimization scheme described with reference to
As an alternative, instead of using a natural breathing pattern as set for the with respect to
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.
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.
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.
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.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10686891 | Oct 2003 | US |
| Child | 10966484 | Oct 2004 | US |
