U.S. patent application number 09/812447 was filed with the patent office on 2001-07-26 for method of treating obstructive sleep apnea using implantable electrodes.
Invention is credited to Loeb, Gerald E., Richmond, Francis J.R..
Application Number | 20010010010 09/812447 |
Document ID | / |
Family ID | 27378197 |
Filed Date | 2001-07-26 |
United States Patent
Application |
20010010010 |
Kind Code |
A1 |
Richmond, Francis J.R. ; et
al. |
July 26, 2001 |
Method of treating obstructive sleep apnea using implantable
electrodes
Abstract
Electrodes are implanted at strategic locations within a patient
and are then controlled in a manner so as to stimulate muscle and
nerve tissue in a constructive manner which helps open blocked
airways. In a preferred method, at least one microstimulator treats
sleep apnea in an open loop fashion by providing electrical
stimulation pulses in a rhythm or cycle having a period
corresponding approximately to the natural respiratory rhythm of
the patient. Such open loop stimulation entrains the patient's
respiratory rate to follow the pattern set by the microstimulator
so that stimulation is applied to open the airway during a period
of inspiration by the patient.
Inventors: |
Richmond, Francis J.R.;
(South Pasadena, CA) ; Loeb, Gerald E.; (South
Pasadena, CA) |
Correspondence
Address: |
ADVANCED BIONICS CORPORATION
12740 SAN FERNANDO ROAD
SYLMAR
CA
91342
US
|
Family ID: |
27378197 |
Appl. No.: |
09/812447 |
Filed: |
March 20, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09812447 |
Mar 20, 2001 |
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09370082 |
Aug 6, 1999 |
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6240316 |
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60096495 |
Aug 14, 1998 |
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60118840 |
Feb 5, 1999 |
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Current U.S.
Class: |
607/42 ;
607/62 |
Current CPC
Class: |
A61N 1/3601 20130101;
A61N 1/37205 20130101; A61N 1/37288 20130101; A61N 1/3727
20130101 |
Class at
Publication: |
607/42 ;
607/62 |
International
Class: |
A61N 001/36 |
Claims
What is claimed is:
1. A method of treating obstructive sleep apnea (OSA) using an
electrical stimulator controllable to provide electrical
stimulation pulses in accordance with a regular stimulation pattern
having a controlled rhythm comprising: (a) determining an
approximate natural respiration cycle of a patient; (b) positioning
electrodes in or on the patient at a location near the oropharynx
muscles; and (c) applying an electrical stimulus to the electrodes
from the electrical stimulator at a rate that approximates the rate
of a natural respiration cycle, wherein the oropharynx muscles are
stimulated to pull open obstructed airways at a rhythm that is the
same as or close to the natural respiration cycle; wherein the
respiratory rate of the patient is entrained to follow the rhythm
of the electrical stimulator, whereby obstructed airways are kept
open.
2. The method of claim 1 wherein the electrodes comprise part of an
injectable microstimulator, and wherein the positioning of the
electrodes in or on the patient at a location near the oropharynx
muscles comprises injecting the microstimulator so that the
microstimulator is positioned near the oropharynx muscles.
3. The method of claim 2 wherein the step of applying an electrical
stimulus to the electrodes comprises controlling the injectable
microstimulators so that they provide a stimulus at a rate that
approximates the natural respiration rate.
4. The method of claim 1 wherein determining the patient's natural
respiration rate comprises using a diagnostic face mask that
stimulates obstruction and opening of the patient's airway at a
controlled rate.
5. A method of treating obstructive sleep apnea (OSA) using an
electrical stimulator controllable to provide electrical
stimulation pulses in accordance with a regular stimulation pattern
having a controlled rhythm comprising: (a) determining an
approximate natural respiration cycle of a subject; (b) positioning
electrodes near the oropharynx muscles of the subject; and (c)
applying an electrical stimulus to the electrodes to pull open
obstructed airways at a rhythm that is the same as or close to the
natural respiration cycle.
6. The method of claim 5 further comprising adjusting the rate of
the applied stimulus so as to entrain the respiration cycle of the
subject to follow the applied stimulus rate.
7. The method of claim 6 wherein the electrodes comprise part of an
injectable microstimulator, and wherein positioning the electrodes
near the oropharynx muscles comprises injecting the microstimulator
so that the microstimulator is positioned near the oropharynx
muscles.
8. The method of claim 6 wherein determining an approximate natural
respiration cycle of the subject comprises using a diagnostic face
mask that stimulates obstruction and opening of the subject's
airway at a controlled rate.
Description
[0001] This application is a divisional application of U.S.
application Ser. No. 09/370,082, filed Aug. 6, 1999, which
application, including its Appendix A filed therewith, is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a system and method for
treating sleep apnea, and more particularly to a system and method
for treatment of obstructive sleep apnea using implantable
microstimulators.
[0003] Sleep apnea is the inability to breath while sleeping. The
most common cause is a mechanical obstruction of the airway. This
can arise from a variety of causes acting at a variety of sites, as
described in detail by the report of Dr. Frances J. R. Richmond
(attached as Appendix A to the parent application, Ser. No.
09/370,082). At each of these sites, various muscles are available
whose mechanical action can be used to open the airway. Thus, in
principle, it should be possible to stimulate these muscles
electrically at appropriate times during sleep to produce
contractions that maintain patency or open an obstructed airway. It
may also be possible to produce muscle contractions via reflexes.
Sensory axons that are present in the muscle nerves or in separate
nerves supplying skin or mucous membranes may have connections in
the spinal cord or brain stem to the motor neurons that control
these muscles. Electrical stimulation of these sensory axons would
then result in the desired muscle contractions.
[0004] Unfortunately, the muscles that control the airway and the
nerves that supply them are, for the most part, located deep in the
neck and oropharynx, adjacent to many vital and delicate
structures. The present invention describes an approach in which
very small electronic devices can be implanted with minimal
surgical intervention in order to control these muscles to prevent
or interrupt sleep apnea without disturbing the sleeping
patient.
[0005] Obstructive sleep apnea (OSA) is characterized by frequent
periods of airway occlusion during sleep, with concomitant
obstruction of inspiratory airflow, drop in blood oxygen and
interruption of sleep when the patient awakes to use voluntary
muscle contraction to open the airway and take a few deep breaths.
The mechanical locations and structural causes of obstruction are
multiple. The most frequent mechanisms include settling of the
tongue, uvula, soft palate or other tissues against the airway
during the negative pressure associated with inspiration. This may
be related to adipose tissue accumulation, lack of muscle tone or
inadequate central respiratory drive to the tongue and/or other
accessory respiratory muscles around the oropharyngeal airway.
[0006] Current treatments for OSA include behavioral control of
sleep posture (e.g. sewing a tennis ball in the back of a pajama
shirt), positive airway pressure applied via a face mask and
ventilating pump, and surgical reduction of the soft tissues in the
airway. Disadvantageously, patient compliance with noninvasive
methods is low. Clinical success rates with surgery are mixed
because the exact mechanical problem is often unclear, the extent
of the surgery is limited for practical reasons, and the soft
tissue may regrow.
[0007] Recently, a fully implanted system using functional
electrical stimulation has been developed in a collaboration
between Johns Hopkins University and Medtronic Corp. It includes an
implanted pressure sensor, electronic controller and a nerve cuff
electrode on the genioglossal nerve, which is used to stimulate the
motor axons that control tongue protrusion. The onset of each
inspiratory phase is detected by sensing the negative pressure wave
under the manubrium of the sternum, which triggers a preset train
of stimuli that causes the tongue muscles to contract, lifting it
away from the posterior oropharynx to prevent occlusion from
occurring. In a small clinical trial, this system had some success,
but it is highly invasive and prone to complications from the
surgical placement of the sensor and nerve cuff. Furthermore, the
algorithm for detecting the onset of inspiration is complex and
prone to error as a result of mechanical artefacts from cardiac
pulsation and postural movements.
[0008] Electrical stimulation of muscles with intact motor supply,
such as in OSA patients, typically involves activation of the large
diameter axons of the motor neurons that, in turn, activate the
muscle fibers to contract. Electrical stimulation may be achieved
by several routes. Transcutaneous electrical and magnetic
stimulation are noninvasive but relatively nonselective, usually
producing substantial activation of cutaneous sensory nerves that
results in intrusive and often disagreeable sensations. Nerve trunk
stimulation via surgically implanted nerve cuff or epineural
electrodes stimulates both the motor and sensory axons that run in
those nerves. The largest diameter fibers of both types tend to be
excited first and there is little conscious sensation associated
with the large diameter proprioceptive fibers in muscle, as opposed
to cutaneous, nerves. However, it is thus difficult to achieve
reliable stimulation of only the largest fibers because the
recruitment curves are relatively steep. Muscle nerves do contain
smaller diameter sensory fibers that signal pain, pressure and
other undesirable sensations. Furthermore, many muscle nerves
supply axons to multiple muscles or compartments of muscles that
may have different and perhaps undesirable actions. For example,
the more proximal and surgically accessible portion of the
genioglossal nerve supplies portions of the tongue muscles that
actually retract rather than protrude the tongue. Intramuscular
wires tend to recruit motor and proprioceptive axons in only the
compartment of muscle in which they are located, but they are
difficult to implant and maintain without migration or breakage as
a result of the constant motion of the muscle and the traction of
attached leads. It is thus seen that there is a need for a better
vehicle for treating obstructive sleep apnea than has heretofore
been available.
[0009] Respiration can be viewed as an oscillator whose frequency
is determined by several different neural and mechanical control
loops involving metabolic rate, neural sensing of oxygen and carbon
dioxide levels in the blood stream, respiratory muscle activity,
airway impedance and tidal volume. Individuals with normal airways
tend to have fairly regular respiratory rhythms punctuated by
occasional irregularities such as deep sighs that help to clear
poorly ventilated portions of the lung and keep alveoli inflated.
Conscious and semiconscious individuals can be ventilated
artificially by a respirator that applies positive pressure to
force air into the lungs at a regular interval, but it is often
difficult to match the ventilation so applied to the perceived need
for air by the patient and his/her nervous system, which may result
in the patient "fighting" the ventilator. Nevertheless, biological
oscillators are easily entrained to periodic external events as
long as the frequency of those events is sufficiently close to the
natural period of the biological oscillator. This is a general
property of systems of loosely coupled oscillators, as originally
described mathematically by Arthur T. Winfree (The Geometry of
Biological Time, Springer Study Edition, 1991) and may also reflect
plastic properties of the nervous system that underlie learning and
adaptive control for many sensorimotor behaviors.
SUMMARY OF THE INVENTION
[0010] In contrast to all of the above approaches for treating
obstructive sleep apnea, or OSA, the present invention teaches the
use of microminiature, leadless stimulators called Bionic Neurons,
or BION.TM. stimulators, or "microstimulators", that receive power
signals (and/or, in some embodiments, recharging signals) and
control signals by inductive or RF coupling to a radio frequency
magnetic field generated outside the body. Such "microstimulators"
are implanted at strategic locations within the patient and
controlled in a manner so as to stimulate muscle and nerve tissue
in a constructive manner to help open blocked airways. Thus, it is
seen that a key aspect of the present invention is that obstructive
sleep apnea is treated by electrically stimulating certain muscles
of the oropharynx using one or more microstimulators in order to
contract and thereby pull open the obstructed airway.
[0011] It should be noted that the present invention is not
directed to the "microstimulator", per se, which is the subject of
other patents and patent applications, but is rather directed to a
method of using the microstimulator, or a group of
microstimulators, to treat sleep apnea.
[0012] As indicated, the invention teaches the treatment of sleep
apnea by electrical stimulation of nerves and muscles by means of
one or more microstimulators located at the site(s) of stimulation.
Advantageously, one or more such devices may be easily implanted
into the desired locations in the body using minimally invasive,
outpatient procedures under local anesthesia. Additionally, such
devices receive power and programming (control) signals by
inductive or RF coupling from an external transmitter, either
during actual use by the sleeping patient or during recharging
periods in the awake patient.
[0013] The microstimulator used with the invention has the
following important properties:
[0014] (1) A narrow, elongated form factor suitable for
implantation through the lumen of a hypodermic needle or
laparoscopic instrument;
[0015] (2) Electronic components encapsulated in a hermetic package
made from a biocompatible material;
[0016] (3) At least two electrodes on the outside of the package
for the application of stimulation current to surrounding
tissue;
[0017] (4) An electrical coil inside the package that receives
power and data by inductive coupling to a transmitting coil placed
outside the body, avoiding the need for electrical leads to connect
devices to a central implanted or external controller; and
[0018] (5) Means for temporary storage of electrical power within
the microstimulator.
[0019] An implantable microstimulator having the above properties
is also known as a BION.TM. stimulator. The BION stimulator is
fully described in other documents, referenced below.
[0020] Two main embodiments of the invention are contemplated, one
closed loop, and one open loop.
[0021] In the closed loop embodiment, the microstimulator devices
also provide a sensing function that can be used to trigger the
desired stimulation whenever airway obstruction is detected.
[0022] In the open loop embodiment, one or more channels of
electrical stimulation are applied to nerves or muscles that
control the oropharyngeal airway and are then activated in a
regular pattern whose period corresponds approximately to the
natural respiratory rhythm of the patient. In this open loop
embodiment, electrical stimulation is thus applied via the BION
stimulator(s) in an open-loop manner, without the complication of
additional sensors and other circuits, as are commonly used in a
closed loop system. Applied stimulation in such open-loop fashion
advantageously entrains the natural biological oscillator
associated with the patient's respiration rate, thereby allowing
the desired opening of the airwaves to occur during inspiration by
the patient.
[0023] Further, in accordance with another aspect of the open loop
embodiment, the natural frequency of respiration of the patient is
determined by observing the patient during sleep, preferably in a
posture that minimizes airway obstruction. Such is determined,
e.g., by visual observation and a stopwatch, or it can be automated
by any of several technologies for monitoring respiration, such as
length gauge monitoring of chest expansion, airflow monitoring
through a face mask, thoracic electrical impedance, and the like.
One or more channels of microstimulators, or BION stimulators, are
then "implanted" in the patient. The individual devices are
injected into the desired muscles after verifying the correct
location of the insertion needle by electrical stimulation of a
removable trochar within the hollow sheath of the needle.
Ultrasonic imaging of the needle, implants and oropharyngeal
structures may also be used during the implantation procedure.
After allowing time for the implanted stimulators to stabilize,
they are powered up and tested with a range of stimulation
parameters (pulse width, current and frequency) to determine the
stimulation program that will open the airway. This program is then
loaded into a portable controller, which is positioned to control
the microstimulators; or, for some embodiments of the
microstimulators, may be loaded directly into the
microstimulators.
[0024] It is thus an object of the present invention to provide a
minimally invasive electrical stimulation system for treatment of
obstructive sleep apnea (OSA).
[0025] It is an additional object of the invention to provide a
method of treating sleep apnea through the use of at least one
small, implantable microstimulator.
[0026] It is another object of the invention to provide a system
and method of treating sleep apnea using at least one tiny
microstimulator that is minimally invasive to the patient, and
which, when the microstimulator(s) is implanted, may be used in
either an open loop or closed loop manner, and which is readily
adaptable (programmable and/or controllable) to suit the diverse
and individual needs of the patient.
[0027] It is a further object of the invention to provide a system
and method for the treatment of OSA that when used in an open loop
manner provides electrical stimulation in a regular pattern whose
period corresponds approximately to the natural respiratory rhythm
of the patient, and thereby entrains the natural respiratory rhythm
of the patient to track that of the applied stimulation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The above and other aspects, features and advantages of the
present invention will be more apparent from the following more
particular description thereof, presented in conjunction with the
following drawings and Appendices wherein:
[0029] FIG. 1 illustrates one way in which a microstimulator may be
used to treat sleep apnea in accordance with the invention;
[0030] FIGS. 2 and 3 respectively illustrate ways in which control
and/or energy signals may be sent to control and/or energy-storage
elements within an implantable microstimulator during sleep (FIG.
2) and during non-sleep (FIG. 3) conditions;
[0031] FIG. 4 illustrates the use of at least two BION devices and
an external controller/recharging unit;
[0032] FIG. 5 illustrates the use of two BION devices used in a
closed-loop system to treat sleep apnea, one having a built-in
sensor that is able to sense a blocked airway and communicate such
sensed data to the other BION device, which other BION device then
initiates a stimulation sequence aimed at unblocking the airway
passage;
[0033] FIG. 6 illustrates an alternate method of coupling the
external controller/recharging unit with the implanted
microstimulator devices;
[0034] FIG. 7 illustrates a multichannel stimulation system using
battery-powered microstimulators; and
[0035] FIG. 8 depicts one manner in which the invention may be
tested using a special type of face mask.
[0036] Corresponding reference characters indicate corresponding
components throughout the several views of the drawings.
DETAILED DESCRIPTION OF THE INVENTION
[0037] The following description is of the best mode presently
contemplated for carrying out the invention. This description is
not to be taken in a limiting sense, but is made merely for the
purpose of describing the general principles of the invention. The
scope of the invention should be determined with reference to the
claims.
[0038] As indicated above, the present invention is directed to a
method for treating sleep apnea, and more particularly obstructive
sleep apnea (OSA) using one or more small implantable
microstimulators, also referred to as BION.TM. m devices. Various
features and details associated with the manufacture, operation and
use of such implantable microstimulators, or BION devices, may be
found in one or more of the following documents, all of which are
incorporated herein by reference: U.S. Pat. No. 5,193,539, entitled
"Implantable Microstimulator"; U.S. Pat. No. 5,193,540, entitled
"Structure and Method of Manufacture of an Implantable
Microstimulator"; U.S. Pat. No. 5,312,439, entitled "Implantable
Device Having an Electrolytic Storage Electrode"; PCT Publication
WO 98/37926, published Sep. 3, 1998, entitled "Battery-Powered
Patient Implantable Device"; PCT Publication WO 98/43700, published
Oct. 8, 1998, entitled "System of Implantable Devices For
Monitoring and/or Affecting Body Parameters"; PCT Publication WO
98/43701, published Oct. 8, 1998, entitled "System of Implantable
Devices For Monitoring and/or Affecting BodyParameters"; U.S.
patent application Ser. No. 09/077,662, filed May 29, 1998,
entitled "Improved Implantable Microstimulator and Systems
Employing Same"; and Cameron, et al., "Micromodular Implants to
Provide Electrical Stimulation of Paralyzed Muscles and Limbs",
IEEE Transactions on Biomedical Engineering, Vol. 44, No. 9
(September 1997), pages 781-790.
[0039] As described in the referenced documents, the
microstimulator or BION.TM. device is a very versatile device that
may be used for many applications. Advantageously, such device has
a form factor that allows it to be readily implanted through the
lumen of a hypodermic needle or laparoscopic instrument, thereby
allowing its implantation to occur in a non-invasive manner. (For
purposes of this application, "non-invasive" or "noninvasively" is
defined to mean without making surgical incisions at the surface
tissue of the patient, i.e., no more invasive than the insertion of
a hypodermic needle.) Typically, the microstimulator is housed
within a tubular housing having a diameter no greater than about
3-4 mm, preferably only about 1.5 mm, and a length no greater than
about 10-12 mm. One way to characterize the microstimulator housing
is by form factor. As used herein, the term "form factor" is
defined as the ratio of the diameter of the housing to its length.
The form factor of a preferred microstimulator is 0.4 or less.
[0040] Like all newly developed devices, the BION.TM. device has
undergone (and is currently undergoing) various stages of
development. At present, there are three levels of BION technology,
any one of which may be used to treat obstructive sleep apnea in
accordance with the invention. These three levels of BION
technology are referred to herein as BION-1 devices, BION-2
devices, and BION-3 devices. A summary of each type of device is
provided below.
[0041] The BION-1 device provides on-line, inward transmission of
power and stimulus command data. The BION-1 system has been built
and tested extensively in animals and clinical trials will begin
shortly in other applications. It is described in detail in the
documents referenced above. The external coil transmits a
continuous RF field with amplitude modulation to encode digital
data. Each implant receives the RF energy, converts it into a
regulated DC supply to operate its integrated circuit chip, and
stores stimulus pulse energy in a capacitor (either discrete
capacitor in the hermetic package or an electrolytic capacitor
formed by the stimulating electrodes themselves and the saline body
fluids). When the implant receives the appropriate command data, it
generates the required stimulation pulse releasing energy stored in
the capacitor, and then recharging the capacitor between output
pulses.
[0042] The BION-2 device provides on-line, inward power
transmission plus bidirectional data transmission supporting
sensing and telemetry functions. The BION-2 devices utilize a new
scheme for data transmission called "suspended carrier
transmission". Suspended carrier transmission is about ten times
more efficient than the transmission scheme utilized with BION-1
devices (thereby making it possible for BION devices to be powered
by battery-operated controllers) and it permits the power
transmission carrier to be switched off for brief periods so that
the implants can sense low level signals and telemeter out data on
the same carrier frequency without being overwhelmed by the strong
power carrier signal. Suspended carrier transmission is described
in U.S. Pat. No. 5,697,076, incorporated herein by reference.
[0043] Advantageously, one potentially important function of the
BION-2 (and BION-3) devices is the ability of one BION implant
device to monitor the outgoing data transmission from another BION
implant device. This can be used to relay sensing and command
signals between implants and to monitor the relative distance and
orientation between two implants in order to measure mechanical
motion of the tissues in which the BION devices are implanted. For
example, the attempt to suck air through an obstructed airway is
likely to be accompanied by various deformations of the normal size
and position of airway structures such as the trachea and larynx,
which deformations may be sensed by continuously monitoring the
relative position between one BION device attached to the moveable
structure and another BION device attached to an adjacent reference
structure. One such deformation is retraction, in which the
obstructed larynx and trachea are stretched downward by the
inspiratory effort of the diaphragm.
[0044] Another approach that may be used with the BION-2 devices to
facilitate sensing various parameters is to detect the
electromyographic signals in accessory respiratory muscles of the
neck and/or chest. These muscles are normally relatively quiescent
during unobstructed respiration, but become active when additional
inspiratory effort is applied as the sleeping patient tries to
overcome the obstruction. Both the BION-2 device and BION-3 device
are being designed to detect such low level bioelectric signals.
While the detection of electromyographic signals is complicated
somewhat by activation of these accessory respiratory muscles
during turning and other postural shifts, such complications are
overcome by additional sensing of acceleration of BION implant
devices, another capability included within selected versions of
BION devices.
[0045] The BION-3 device includes bidirectional data telemetry plus
a rechargeable battery (or other power storage component, such as
an ultracapacitor) permitting autonomous function in the absence of
external power transmission. Preferably, each BION 3 device is
powered by a miniature rechargeable battery (e.g., lithium ion
technology) within its hermetic package, as described in some of
the above-referenced documents. The internal battery is capable of
sustaining internal clocking and logic and output pulses for a
period of hours to days (depending on stimulus parameters). The
internal battery, or other power source, is recharged during
relatively brief periods of time, e.g., 10-30 minutes, when the
BION implant devices receive power from an external coil.
Stimulation parameters and other control functions are updated by
data transmission from the external controller at this time. A
simple means for manually starting and stopping preprogrammed
operation is also provided, such as a portable magnet or RF
transmitter that may be worn by the patient.
[0046] Turning next to the figures, the method of using BION.TM.
devices for treating obstructive sleep apnea in accordance with the
various embodiments of the invention will be described. Many
different combinations of devices and functions are possible for
stimulation, power, sensing and control. The following descriptions
are intended to be illustrative only of the various ways a
microstimulator may be used to treat sleep apnea, and are not
intended to be limiting. It should also be noted that the
accompanying drawings are not drawn to scale. In actuality, the
BION devices are very tiny, about the size of a large grain of
rice.
[0047] As seen in FIG. 1, for example, one or more BION implant
devices 10 receive power and command signals from a transmission
coil 26 placed under the patient 1. The transmission coil, for
example, may be placed in the pillow or mattress cover 20. An
external bedside controller 24 that is powered from conventional
power lines sends a preprogrammed sequence of stimulation commands
to the implant device(s) 10, causing them to stimulate motor and/or
sensory nerves at target sites 5. This electrical stimulation, in
turn, results in direct or reflexive muscular contraction that
opens the airway continuously or at regular intervals during
sleep.
[0048] In one embodiment, as seen, e.g., in FIGS. 1, 2 or 3, one or
more BION 3 implant devices 10 use energy stored in their
rechargeable batteries to stimulate motor and/or sensory nerves at
target sites 5, resulting in direct or reflexive muscular
contraction that opens the airway continuously or at regular
intervals during sleep. The batteries in the BION 3 implant devices
10 are recharged as required by donning a transmission coil 26 that
is connected to a controller 24 that receives its power from
conventional power lines. The controller 24 transmits data
specifying the stimulation parameters to reassert or modify the
stimulation pulses that will be generated when the BION-3 implants
are operating. As needed, the patient 1 can turn the BION-3
implants on or off by operating a portable remote control device
28.
[0049] In another embodiment, a closed loop embodiment, one or more
BION-2 implant devices 10 are implanted in the patient 1, as
illustrated in FIG. 4, with at least one such BION-2 implant device
acting as a sensor of airway occlusion. The sensing function is
realized, e.g., utilizing airway pressure, characteristic snoring
sounds, mechanical motion, muscle activity or other means for
detecting occlusion. Information from the sensing function is
transmitted from the sensing BION device to an external bedside
controller 24, which utilizes such information to decide when and
what stimulation is required to alleviate the occlusion, according
to prescribing information stored in the bedside controller 24 by
the clinician. The bedside controller 24 transmits stimulation
commands to one or more of the BION-2 implant devices. Data
transmission in both directions is conveyed via a transmission coil
26 placed under the sleeping patient, for example in the pillow or
mattress cover 20.
[0050] In still a further embodiment, also represented by the
configuration shown in FIG. 4, one or more BION-3 implant devices
10 perform both sensing and stimulus functions according to control
information stored within the BION-3 implant devices. Power to
recharge the batteries included as part of the BION-3 devices 10,
as well as control signals to operate the BION-3 device according
to a prescribed operating program, are transmitted to the BION-3
implants during occasional recharging periods, using a suitable
external recharging/programming unit 24, at which time the patient
dons a transmission coil 26, as shown in FIG. 3, or lies adjacent a
transmission coil 26, as shown in FIG. 4, that is connected to a
controller 24. The controller 24 receives its power from
conventional power lines or from a removable, replaceable
battery.
[0051] In yet another embodiment, illustrated in FIG. 5, at least
one BION implant device 10 functions as a transmitter and transmits
sensor data concerning airway occlusion to at least one other BION
implant device 11. The device 11 thus functions as a receiver and
uses the received data to initiate a stimulation sequence that has
been previously stored in the BION device 11.
[0052] With reference to FIG. 6, it is noted that when power and
data transmission are conveyed via a transmission coil 26 worn on
the patient, such coil 26 may be included as part of a collar
around the neck 32, a vest 33, or other suitably located garment.
Alternatively, the coil 26 may be contained within an adhesive
patch that can be affixed to the skin in the vicinity of the BION
implant device(s).
[0053] The transmission coil 26 may be controlled and powered by
electronic circuitry 22 containing batteries 23 for power, as seen
in FIG. 6. Such circuitry 22 may also be worn on the patient; as
shown in FIG. 6, or such circuitry may be controlled and powered
via an electrical cable 38 that tethers the patient to a bedside
controller 24, as seen in FIG. 3. The bedside controller, in turn,
receives its operating power from conventional power lines or from
replaceable batteries.
[0054] Advantageously, an implanted battery-powered
microstimulator, e.g., a BION-3 device, may be programmed to
self-generate the desired stimulation pattern at a desired rate. If
more than one channel of stimulation is desired, it is necessary to
have more than one battery-powered microstimulator implanted, as
well as a means to synchronize the operation of the various
autonomous implants. This may be done as illustrated in FIG. 7. As
seen in FIG. 7, at least one microstimulator 10T functions as a
transmitter, emitting energy that the other microstimulators 10R
can receive and detect. In one embodiment, the energy emitted by
the microstimulator 10T is in the form of the stimulation pulse
itself produced by the transmitting microstimulator 10T, which is
detected as a stimulus artefact on the electrodes of receiving
microstimulators 10R. Alternatively, the energy emitted by the
microstimulator 10T may be a pulse of radio frequency energy
detected by mutual inductance between the coils contained within
each receiving microstimulator 10R.
[0055] The transmitting microstimulator 10T is programmed to
stimulate the tissue in which it is located and to transmit to the
other implant microstimulator devices at the desired respiratory
rate. The receiving microstimulators 10R are programmed to generate
stimuli if and only if they detect the energy emitted by
transmitting microstimulator 10T. For BION-3 devices, i.e.,
battery-powered microstimulators 10, means are also provided to
start and stop the autonomous function, to download revised
stimulation parameters, and to recharge the batteries at regular
intervals. All of these functions may be accomplished by inward RF
power and telemetry links as depicted in FIGS. 1, 2, 5 and 6.
[0056] In order to use the microstimulator in an open loop system
wherein electrical stimuli are applied to open the blocked airway
passage at a rate that approximates the patient's natural
respiratory rate, it is first necessary to determine that patient's
natural respiratory rate, and then determine if such natural rate
can be entrained to follow the rate of the applied stimuli. This
may be accomplished as illustrated in FIG. 8.
[0057] As shown in FIG. 8, the patient 1, while in a lying or
sleeping position, is fitted with a face mask 201. The face mask
201 is equipped with a flap valve 220 coupled by mechanical means
240 to an electromechanical actuator 260, such as a solenoid or
motor. In its passive state, the flap valve 220 simulates OSA by
occluding the inlet passage to the mask on inspiration only.
Activation of the electromechanical actuator 260 simulates regular
periods of oropharyngeal muscle stimulation by holding the passage
open at the desired intervals. The subject falls asleep with the
flap valve 220 held open; then the open/closed cycling is applied
by controller 350 to see if the subject is able to breath
adequately.
[0058] One important observation obtained from using a system like
that illustrated in FIG. 8 is the pattern of respiration that
ensues when the valve 220 happens to be closed at the time of an
inspiration, mimicking the typical airway obstruction. This occurs
in a system using microstimulator implants, as described, e.g.,
above in connection with FIGS. 1-6, following a prolonged
respiratory interval such as a sigh or a phase shift of the normal
rhythm, e.g., as occurs during a postural shift. When this
prolonged respiratory interval occurs, the occluded inspiratory
phase is prolonged so that it persists until the valve 220 is
opened electronically, or the subsequent inspiratory phases will be
gradually phase-shifted so that they coincide with a valve-open
period within a couple of cycles.
[0059] The entraining technique shown in FIG. 8 is a simple,
noninvasive procedure that may easily be carried out in a
conventional sleep disorders diagnostic laboratory. The mask 201 is
readily made by those of skill in the art of biomedical
engineering. Until sufficient data is developed to show otherwise,
and because patients may likely differ in their patterns of
response to an occlusion occasioned by wearing the mask, extensive
individual testing of prospective patients for receipt of the
implanted microstimulators 10 is highly recommended.
[0060] As described herein, it is thus seen that the invention
provides a method of treating sleep apnea through the use of at
least one small, implantable microstimulator. Such method includes
implanting at least one BION implant device near a target site
containing muscle and/or nerve tissue, and thereafter controlling
the at least one BION implant device to apply electrical stimuli to
the muscle and/or nerve tissue in accordance with a prescribed
stimulation regime, which stimulation regime is aimed at opening up
the blocked airway. For example, a burst of n stimulation pulses,
where n is an integer of e.g., 2 to 20, or more, may be applied to
muscle tissue near the blocked airway upon sensing a blockage.
Alternatively, a burst of n stimulation pulses may be regularly
applied to a patient having a history of blocked airways on a
regular basis, while the patient is sleeping. Or, a single
stimulation pulse may be applied to targeted tissue of the sleeping
patient on a regular basis, or when a blockage is sensed. Indeed,
many different types of stimulation sequences may be applied to
appropriate tissue and/or nerves in order to achieve the objectives
of the invention (i.e., to cause a muscle contraction that opens a
blocked airway).
[0061] As further described herein, it is seen that the invention
provides a system and method of treating sleep apnea that is
minimally invasive to the patient, and which, once implanted, is
readily adaptable (programmable and/or controllable) to suit the
diverse and individual needs of the patient. In one embodiment, the
implantable microstimulators are used in an open loop manner and
assist in entraining the respiratory rate of the patient to match
the programmed rate of the microstimulator(s). In another
embodiment, the implantable microstimulators are used in
conjunction with one or more sensors in a closed loop manner, and
assist in stimulating target tissue at an appropriate time in the
respiratory cycle.
[0062] While the invention herein disclosed has been described by
means of specific embodiments and applications thereof, numerous
modifications and variations could be made thereto by those skilled
in the art without departing from the scope of the invention set
forth in the claims.
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