U.S. patent application number 11/047232 was filed with the patent office on 2005-06-16 for method and system for vagal blocking with or without vagal stimulation to provide therapy for obesity and other gastrointestinal disorders using rechargeable implanted pulse generator.
Invention is credited to Boveja, Birinder R., Widhany, Angely.
Application Number | 20050131486 11/047232 |
Document ID | / |
Family ID | 34704997 |
Filed Date | 2005-06-16 |
United States Patent
Application |
20050131486 |
Kind Code |
A1 |
Boveja, Birinder R. ; et
al. |
June 16, 2005 |
Method and system for vagal blocking with or without vagal
stimulation to provide therapy for obesity and other
gastrointestinal disorders using rechargeable implanted pulse
generator
Abstract
Method and system to provide therapy for obesity and
gastrointestinal disorders such as FGIDs, gastroparesis,
gastro-esophageal reflex disease (GERD), pancreatitis and ileus
comprises vagal blocking and/or vagal stimulation, utilizing
implanted and external components. Vagal blocking may be in the
afferent or efferent direction, and may be with or without
selective stimulation. Blocking may be provided by one of a number
of different electrical blocking techniques. The implantable
components are a lead and an implantable pulse generator (IPG),
comprising re-chargeable lithium-ion or lithium-ion polymer
battery. The external components are a programmer and an external
recharger. In one embodiment, the implanted pulse generator may
also comprise stimulus-receiver means, and a pulse generator means
with rechargeable battery. In another embodiment, the implanted
pulse generator is adapted to be rechargeable, utilizing inductive
coupling with an external recharger. Existing nerve stimulators may
also be adapted to be used with rechargeable power sources as
disclosed herein. The implanted system comprises a lead with two or
more electrodes, for vagus nerve(s) modulation with selective
stimulation and/or blocking. In another embodiment, the external
stimulator and/or programmer may comprise an optional telemetry
unit. The addition of the telemetry unit to the external stimulator
and/or programmer provides the ability to remotely interrogate and
change stimulation programs over a wide area network, as well as
other networking capabilities.
Inventors: |
Boveja, Birinder R.;
(Milwaukee, WI) ; Widhany, Angely; (Milwaukee,
WI) |
Correspondence
Address: |
BIRINDER R. BOVEJA & ANGELY WIDHANY
P. O. BOX 210095
MILWAUKEE
WI
53221
US
|
Family ID: |
34704997 |
Appl. No.: |
11/047232 |
Filed: |
January 31, 2005 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11047232 |
Jan 31, 2005 |
|
|
|
11035374 |
Jan 13, 2005 |
|
|
|
11035374 |
Jan 13, 2005 |
|
|
|
10841995 |
May 8, 2004 |
|
|
|
10841995 |
May 8, 2004 |
|
|
|
10196533 |
Jul 16, 2002 |
|
|
|
10196533 |
Jul 16, 2002 |
|
|
|
10142298 |
May 9, 2002 |
|
|
|
Current U.S.
Class: |
607/40 ;
607/58 |
Current CPC
Class: |
A61N 1/36082 20130101;
A61N 1/40 20130101; A61N 1/36007 20130101; A61N 1/36071 20130101;
A61N 1/3627 20130101; A61N 1/36114 20130101 |
Class at
Publication: |
607/040 ;
607/058 |
International
Class: |
A61N 001/18 |
Claims
What is claimed is:
1. A method of providing electrical pulses with rechargeable
implantable pulse generator for nerve blocking with or without
selective electrical stimulation of vagus nerve(s) or its branches
or part thereof for treating, controlling, or alleviating the
symptoms for at least one of obesity, motility disorders, eating
disorders, inducing weight loss, FGIDs, gastroparesis,
gastro-esophageal reflex disease (GERD), pancreatitis, and ileus,
comprising the steps of: providing said rechargeable implantable
pulse generator, comprising a microcontroller, pulse generation
circuitry, rechargeable battery, battery recharging circuitry, and
a coil; providing a lead with at least two electrodes adapted to be
in contact with said nerve tissue, and in electrical contact with
said rechargeable implantable pulse generator; providing an
external power source to charge said rechargeable implantable pulse
generator; and providing an external programmer to program said
rechargeable implantable pulse generator.
2. A method of claim 1, wherein said nerve blocking comprises
selective blocking of nerve impulses of a vagus nerve(s), its
branch(es) or part thereof, at one or more sites with said
electrical pulses.
3. A method of claim 1, wherein said electrical pulses are for at
least one of afferent block, efferent block, or organ block.
4. A method of claim 1, wherein nerve blocking may also be provided
to alleviate the side effects of nerve stimulation therapy.
5. A method of claim 1, wherein said nerve blocking comprises at
least one from a group consisting of: DC or anodal block, Wedenski
block, and Collision block.
6. A method of claim 1, wherein said rechargeable implantable pulse
generator further comprises stimulus-receiver means such that, said
implantable rechargeable pulse generator can also function in
conjunction with an external stimulator, to provide said electrical
pulses for said nerve blocking and/or stimulation.
7. A method of claim 1, wherein said external power source to
recharge said rechargeable implantable pulse generator can be an
external re-charger or an external stimulator.
8. A method of claim 1, wherein said coil used in recharging said
pulse generator is around said implantable rechargeable pulse
generator case in a silicone enclosure.
9. A method of claim 1, wherein said rechargeable implanted pulse
generator further comprises one or two feed-through(s) for
externalizing coils, for unipolar or bipolar configurations
respectively.
10. A method of claim 1, wherein said at least two electrodes are
made of a material selected from the group consisting of platinum,
platinum/iridium alloy, platinum/iridium alloy coated with titanium
nitride, and carbon.
11. A method of claim 1, wherein said rechargeable battery
comprises at least one of lithium-ion, lithium-ion polymer
batteries.
12. A method of claim 1, wherein said rechargeable implanted pulse
generator is adapted to be remotely interrogated and/or programmed
over a wide area network by an external interface means.
13. A method of providing electrical pulses with rechargeable
implantable pulse generator for vagal blocking with or without
selective vagal stimulation for treating or alleviating the
symptoms for at least one of obesity, eating disorders, inducing
weight loss, FGIDs, gastroparesis, gastro-esophageal reflex disease
(GERD), pancreatitis, and ileus, comprising the steps of: providing
an implantable rechargeable pulse generator, wherein said
implantable rechargeable pulse generator comprises a
stimulus-receiver means, and an implantable pulse generator means
comprising a microcontroller, pulse generation circuitry,
rechargeable battery, and battery recharging circuitry; providing a
lead with at least two electrodes adapted to be in contact with
said vagus nerve(s) or its branches or part thereof, and in
electrical contact with said implantable rechargeable pulse
generator; providing an external power source to charge
rechargeable implantable pulse generator; and providing an external
programmer to program the said rechargeable implantable pulse
generator.
14. A method of claim 13, wherein said rechargeable implantable
pulse generator can function in conjunction with an external
stimulator, to provide said blocking to said vagus nerve(s) and/or
its branches with or without said selective stimulation.
15. A method of claim 13, wherein said coil used in recharging said
pulse generator is around said rechargeable implantable pulse
generator case in a silicone enclosure.
16. A method of claim 13, wherein said rechargeable battery
comprises at least one of lithium-ion, lithium-ion polymer
batteries.
17. A system for providing electrical pulses with rechargeable
implantable pulse generator for nerve blocking with or without
selective electrical stimulation of vagus nerve(s) or its branches
or part thereof for treating, controlling, or alleviating the
symptoms for at least one of obesity, motility disorders, eating
disorders, inducing weight loss, FGIDs, gastroparesis,
gastro-esophageal reflex disease (GERD), pancreatitis, and ileus,
comprising: a rechargeable implantable pulse generator, comprising,
a microprocessor, pulse generation circuitry, rechargeable battery,
battery recharging circuitry, and a coil; a lead with at least two
electrodes adapted to be in contact with said nerve tissue and in
electrical contact with said implantable rechargeable pulse
generator; an external power source to charge said rechargeable
implantable pulse generator; and an external programmer to program
said rechargeable implantable pulse generator.
18. A system of claim 17, wherein said nerve blocking comprises at
least one from a group consisting of: DC or anodal block, Wedenski
block, and Collision block.
19. A system of claim 17, wherein said coil is used for
bidirectional telemetry, or receiving electrical pulses from said
external stimulator.
20. A system of claim 17, wherein said coil used in recharging said
pulse generator is around said rechargeable implantable pulse
generator case in a silicone enclosure.
21. A system of claim 17, wherein said rechargeable implanted pulse
generator further comprises one or two feed-through(s) for
externalizing coils, for unipolar or bipolar configurations
respectively.
22. A system of claim 17, wherein said implantable rechargeable
pulse generator further comprises stimulus receiver means such that
said implantable rechargeable pulse generator can also function in
conjunction with an external stimulator, to provide said blocking
with or without stimulation to said vagus nerve(s) and/or its
branches.
23. A system of claim 17, wherein said at least two electrodes are
made of a material selected from the group consisting of platinum,
platinum/iridium alloy, platinum/iridium alloy coated with titanium
nitride, and carbon.
24. A system of claim 17, wherein said rechargeable battery
comprises at least one of lithium-ion, lithium-ion polymer
batteries.
25. A system of claim 17, wherein said rechargeable implanted pulse
generator is adapted to be remotely interrogated and/or programmed
over a wide area network by an external interface means.
Description
[0001] This application is a continuation of application Ser. No.
11/035,374 filed Jan. 13, 2005, entitled "Method and system for
providing electrical pulses for neuromodulation of vagus nerve(s)
using rechargeable implanted pulse generator", which is a
continuation of application Ser. No. 10/841,995 filed May 8, 2004,
which is a continuation of application Ser. No. 10/196,533 filed
Jul. 16, 2002, which is a continuation of application Ser. No.
10/142,298 filed on May 9, 2002. The prior applications being
incorporated herein in entirety by reference, and priority is
claimed from these applications.
FIELD OF INVENTION
[0002] This invention relates generally to providing electrical
pulses for blocking/stimulation therapy for medical disorders, more
specifically to neuromodulation therapy comprising vagal blocking
with or without vagal stimulation, for providing therapy for
obesity and other gastrointestinal (GI) disorders, utilizing
rechargeable implantable pulse generator.
Background of Obesity and Relation to Vagus Nerve
[0003] Obesity is a significant health problem in the United States
and many other developed countries. Obesity results from excessive
accumulation of fat in the body. It is caused by ingestion of
greater amounts of food than can be used by the body for energy.
The excess food, whether fats, carbohydrates, or proteins, is then
stored almost entirely as fat in the adipose tissue, to be used
later for energy. Obesity is not simply the result of gluttony and
a lack of willpower. Rather, each individual inherits a set of
genes that control appetite and metabolism, and a genetic tendency
to gain weight that may be exacerbated by environmental conditions
such as food availability, level of physical activity and
individual psychology and culture. Other causes of obesity also
include psychogenic, neurogenic, and other metabolic related
factors.
[0004] Obesity is defined in terms of body mass index (BMI), which
provides an index of the relationship between weight and height.
The BMI is calculated as weight (in Kilograms) divided by height
(in square meters), or as weight (in pounds) times 703 divided by
height (in square inches). The primary classification of overweight
and obesity relates to the BMI and the risk of mortality. The
prevalence of obesity in adults in the United States without
coexisting morbidity increased from 12% in 1991 to 17.9% in 1998,
and is still increasing.
[0005] Treatment of obesity depends on decreasing energy input
below energy expenditure. Treatment has included among other things
various drugs, starvation, and even stapling or surgical resection
of a portion of the stomach. Surgery for obesity has included
gastroplasty and gastric bypass procedure. Gastroplasty which is
also known as stomach stapling, involves constructing a 15- to 30
mL pouch along the lesser curvature of the stomach. A modification
of this procedure involves the use of an adjustable band that wraps
around the proximal stomach to create a small pouch. Both
gastroplasty and gastric bypass procedures have a number of
complications.
[0006] The vagus nerve (which is the 10.sup.th cranial nerve) plays
a role in mediating afferent information from the stomach to the
satiety center in the brain. The vagus nerve arises directly from
the brain, but unlike the other cranial nerves extends well beyond
the head. At its farthest extension it reaches the lower parts of
the intestines. This is shown schematically in FIG. 1, and in more
detail in FIG. 2.
[0007] In 1988 it was reported in the American Journal of
Physiology, that the afferent vagal fibers from the stomach wall
increased their firing rate when the stomach was filled. One way to
look at this regulatory process is to imagine that the drive to
eat, which may vary rather slowly with the rise and fall of hormone
Leptin, is inhibited by satiety signals that occur when we eat and
begin the digestive process (i.e., the prandial period). As shown
schematically in FIG. 3, these satiety signals both terminate the
meal and inhibit feeding for some time afterward. During this
postabsorptive (fasting) period, the satiety signals slowly
dissipate until the drive to eat again takes over.
[0008] The regulation of feeding behavior involves the concentrated
action of several satiety signals such as gastric distention, the
release of the gastrointestinal peptide cholecystokinin (CCK), and
the release of the pancreatic hormone insulin. The stomach wall is
richly innervated by mechanosensory axons, and most of these ascend
to the brain via the vagus nerve(s) 54. The vagus sensory axons
activate neurons in the Nucleus of the Solitary Tract in the
medulla of the brain. These signals inhibit feeding behavior. In a
related mechanism, the peptide CCK is released in response to
stimulation of the intestines by certain types of food, especially
fatty ones. CCK reduces frequency of eating and size of meals. As
depicted schematically in FIG. 4, both gastric distension and CCK
act synergistically to inhibit feeding behavior.
Vagal Blocking and/or Stimulation
[0009] In commonly assigned disclosures, application Ser. No.
10/079,21 now U.S. Pat. ______, and U.S. Pat. No. 6,611,715, pulsed
electrical neuromodulation therapy for obesity and other medical
conditions is obtained by providing electrical pulses to the vagus
nerve(s) via an implanted lead comprising plurality of electrodes.
In those disclosures, the electrical pulses are provided by at
least one electrode on the lead. This patent application is
directed to system and method for neuromodulation of vagal
activity, wherein vagal block with or without selective vagal
stimulation may be used to provide therapy for obesity, weight
loss, eating disorders, and other gastrointestinal disorders such
as FGIDs, gastroparesis, gastro-esophageal reflex disease (GERD),
pancreatitis, ileus and the like. Even though the invention is
disclosed in the context of vagal blocking, the nerve blocking
methodology can also be used to provide therapy for other ailments,
and to provide electric pulses for blocking of other nerves such as
sympathetic nerve(s), sacral nerves, or other cranial nerves or
their branches or part thereof.
[0010] The gastrointestinal tract and central nervous system (CNS)
engage each other in two-way communication. This has both
parasympathetic and sympathetic components. Of particular interest
in this disclosure is the parasympathetic component or the vagal
pathway, which is shown in conjunction with FIG. 5.
[0011] In some gastrointestinal (GI) disorders, to provide therapy,
stimulation of the vagus nerve(s) is adequate and is the preferred
mode of providing therapy. For other GI disorders, to provide
therapy, stimulation and selective block is the preferred mode of
therapy. For some GI disorders, vagal nerve(s) blocking only is the
preferred mode of providing therapy. Advantageously, the method and
system disclosed in this patent application can provide vagal
blocking with or without vagal stimulation to provide therapy for
obesity and other gastrointestinal disorders.
[0012] As is shown in conjunction with FIG. 6 when vagal pathway is
stimulated, the stimulation is conducted both in the Afferent
(towards the brain) and Efferent (away from the brain) direction.
Shown in conjunction with FIG. 7, by placing blocking electrodes
proximal to the stimulating electrodes, and supplying blocking
pulses, the conduction in the Afferent direction (towards the
brain) can be blocked or significantly reduced. The blocking pulses
may be 500 Hz or other frequency, as described later in this
disclosure. This is useful for certain GI disorders, for example
ileus and the like.
[0013] Shown in conjunction with FIG. 8, the blocking electrodes
may be placed distal to the stimulating electrodes. If the
stimulator provides blocking pulses to the blocking electrode, then
the vagus nerve(s) impulses in the Efferent direction are either
blocked or are significantly reduced. As the vagus nerves are
involved in pancreatitus, the down-regulating of vagal activity can
be used to treat pancreatitus and the like.
[0014] It will be clear to one of ordinary skill in the art, that
by selectively placing the blocking electrode, selective block can
be obtained when the stimulator applies blocking pulses to the
blocking electrode. Selective Efferent block is depicted in
conjunction with FIG. 9. As shown in the figure, because of the
selective placement of blocking electrode(s), only the impulses to
visceral organ 2 are blocked or significantly reduced, and impulses
to visceral organ-1 and visceral organ-2 continue unimpeded.
Selective Afferent block can also be achieved, and is depicted in
conjunction with FIG. 10. Here the nerve impulses to visceral organ
and visceral organ-5 are selectively blocked. An example would be
where Afferent vagal pulses are desired, but impulses to the heart
and vocal cords would be blocked. Thus, advantageously providing
the desired therapy without the side effects of voice or cardiac
complications such as bradycardia. Similarly other side effects can
be alleviated or minimized with nerve blocking.
Background of Neuromodulation
[0015] Most nerves in the human body are composed of thousands of
fibers of different sizes. This is shown schematically in FIG. 11.
The different sizes of nerve fibers, which carry signals to and
from the brain, are designated by groups A, B, and C. The vagus
nerve, for example, may have approximately 100,000 fibers of the
three different types, each carrying signals. Each axon or fiber of
that nerve conducts only in one direction, in normal circumstances.
In the vagus nerve sensory fibers outnumber parasympathetic fibers
four to one.
[0016] In a cross section of peripheral nerve it is seen that the
diameter of individual fibers vary substantially, as is also shown
schematically in FIG. 12. The largest nerve fibers are
approximately 20 .mu.m in diameter and are heavily myelinated
(i.e., have a myelin sheath, constituting a substance largely
composed of fat), whereas the smallest nerve fibers are less than 1
.mu.m in diameter and are unmyelinated.
[0017] The diameters of group A and group B fibers include the
thickness of the myelin sheaths. Group A is further subdivided into
alpha, beta, gamma, and delta fibers in decreasing order of size.
There is some overlapping of the diameters of the A, B, and C
groups because physiological properties, especially in the form of
the action potential, are taken into consideration when defining
the groups. The smallest fibers (group C) are unmyelinated and have
the slowest conduction rate, whereas the myelinated fibers of group
B and group A exhibit rates of conduction that progressively
increase with diameter.
[0018] Nerve cells have membranes that are composed of lipids and
proteins, and have unique properties of excitability such that an
adequate disturbance of the cell's resting potential can trigger a
sudden change in the membrane conductance. Under resting
conditions, the inside of the nerve cell is approximately -90 mV
relative to the outside. The electrical signaling capabilities of
neurons are based on ionic concentration gradients between the
intracellular and extracellular compartments. The cell membrane is
a complex of a bilayer of lipid molecules with an assortment of
protein molecules embedded in it, separating these two
compartments. Electrical balance is provided by concentration
gradients which are maintained by a combination of selective
permeability characteristics and active pumping mechanism.
[0019] A nerve cell can be excited by increasing the electrical
charge within the neuron, thus increasing the membrane potential
inside the nerve with respect to the surrounding extracellular
fluid. The threshold stimulus intensity is the value at which the
net inward current (which is largely determined by Sodium ions) is
just greater than the net outward current (which is largely carried
by Potassium ions), and is typically around -55 mV inside the nerve
cell relative to the outside (critical firing threshold). If
however, the threshold is not reached, the graded depolarization
will not generate an action potential and the signal will not be
propagated along the axon. This fundamental feature of the nervous
system i.e., its ability to generate and conduct electrical
impulses, can take the form of action potentials, which are defined
as a single electrical impulse passing down an axon. This action
potential (nerve impulse or spike) is an "all or nothing"
phenomenon, that is to say once the threshold stimulus intensity is
reached, an action potential will be generated.
[0020] To stimulate an excitable cell, it is only necessary to
reduce the transmembrane potential by a critical amount. When the
membrane potential is reduced by an amount .DELTA.V, reaching the
critical or threshold potential. When the threshold potential is
reached, a regenerative process takes place: sodium ions enter the
cell, potassium ions exit the cell, and the transmembrane potential
falls to zero (depolarizes), reverses slightly, and then recovers
or repolarizes to the resting membrane potential (RMP). For a
stimulus to be effective in producing an excitation, it must have
an abrupt onset, be intense enough, and last long enough.
[0021] Cell membranes can be reasonably well represented by a
capacitance C, shunted by a resistance R as shown by an electrical
model in FIG. 13, where neuronal process is divided into unit
lengths, which is represented in an electrical equivalent circuit.
Each unit length of the process is a circuit with its own membrane
resistance (r.sub.m), membrane capacitance (c.sub.m), and axonal
resistance (r.sub.a).
[0022] When the stimulation pulse is strong enough, an action
potential will be generated and propagated. As shown in FIG. 14,
the action potential is traveling from right to left. Immediately
after the spike of the action potential there is a refractory
period when the neuron is either unexcitable (absolute refractory
period) or only activated to sub-maximal responses by
supra-threshold stimuli (relative refractory period). The absolute
refractory period occurs at the time of maximal Sodium channel
inactivation while the relative refractory period occurs at a later
time when most of the Na.sup.+ channels have returned to their
resting state by the voltage activated K.sup.+ current. The
refractory period has two important implications for action
potential generation and conduction. First, action potentials can
be conducted only in one direction, away from the site of its
generation, and secondly, they can be generated only up to certain
limiting frequencies.
[0023] A single electrical impulse passing down an axon is shown
schematically in FIG. 15. The top portion of the figure (A) shows
conduction over mylinated axon (fiber) and the bottom portion (B)
shows conduction over nonmylinated axon (fiber). These electrical
signals will travel along the nerve fibers.
[0024] The information in the nervous system is coded by frequency
of firing rather than the size of the action potential. In terms of
electrical conduction, myelinated fibers conduct faster, are
typically larger, have very low stimulation thresholds, and exhibit
a particular strength-duration curve or respond to a specific pulse
width versus amplitude for stimulation, compared to unmyelinated
fibers. The A and B fibers can be stimulated with relatively narrow
pulse widths, from 50 to 200 microseconds (.mu.s), for example. The
A fiber conducts slightly faster than the B fiber and has a
slightly lower threshold. The C fibers are very small, conduct
electrical signals very slowly, and have high stimulation
thresholds typically requiring a wider pulse width (300-1,000
.mu.s) and a higher amplitude for activation. Because of their very
slow conduction, C fibers would not be highly responsive to rapid
stimulation. Selective stimulation of only A and B fibers is
readily accomplished. The requirement of a larger and wider pulse
to stimulate the C fibers, however, makes selective stimulation of
only C fibers, to the exclusion of the A and B fibers, virtually
unachievable inasmuch as the large signal will tend to activate the
A and B fibers to some extent as well.
[0025] As shown in FIG. 16, when the distal part of a nerve is
electrically stimulated, a compound action potential is recorded by
an electrode located more proximally. A compound action potential
contains several peaks or waves of activity that represent the
summated response of multiple fibers having similar conduction
velocities. The waves in a compound action potential represent
different types of nerve fibers that are classified into
corresponding functional categories as shown in the Table one
below,
1 TABLE 1 Conduction Fiber Fiber Velocity Diameter Type (m/sec)
(.mu.m) Myelination A Fibers Alpha 70-120 12-20 Yes Beta 40-70 5-12
Yes Gamma 10-50 3-6 Yes Delta 6-30 2-5 Yes B Fibers 5-15 <3 Yes
C Fibers 0.5-2.0 0.4-1.2 No
[0026] Vagus nerve blocking and stimulation, performed by the
system and method of the current patent application, is a means of
directly affecting central function, as well as, peripheral
function. FIG. 17 shows cranial nerves have both afferent pathway
19 (inward conducting nerve fibers which convey impulses toward the
brain) and efferent pathway 21 (outward conducting nerve fibers
which convey impulses to an effector). Vagus nerve (the 10.sup.th
cranial nerve) is composed of 80% afferent sensory fibers carrying
information to the brain from the head, neck, thorax, and abdomen.
The sensory afferent cell bodies of the vagus reside in the nodose
ganglion and relay information to the nucleus tractus solitarius
(NTS).
[0027] The vagus nerve spans from the brain stem all the way to the
splenic flexure of the colon. Not only is the vagus the
parasympathetic nerve to the thoracic and abdominal viscera, it
also the largest visceral sensory (afferent) nerve. Sensory fibers
outnumber parasympathetic fibers four to one. In the medulla, the
vagal fibers are connected to the nucleus of the tractus solitarius
(viceral sensory), and three other nuclei. The central projections
terminate largely in the nucleus of the solitary tract, which sends
fibers to various regions of the brain (e.g., the thalamus,
hypothalamus and amygdala).
[0028] This application is also related to co-pending applications
entitled "METHOD AND SYSTEM FOR PROVIDING ELECTRICAL PULSES TO
GASTRIC WALL OF A PATIENT WITH RECHARGEABLE IMPLANTABLE PULSE
GENERATOR FOR TREATING OR CONTROLLING OBESITY AND EATING DISORDERS"
and "METHOD AND SYSTEM TO PROVIDE THERAPY FOR OBESITY AND OTHER
MEDICAL DISORDERS, BY PROVIDING ELECTRICAL PULSES TO SYMPATHETIC
NERVES OR VAGAL NERVE(S) WITH RECHARGEABLE IMPLANTED PULSE
GENERATOR.
PRIOR ART
[0029] Prior art is generally directed to adapting cardiac
pacemaker technology for nerve stimulation, where U.S. Pat. Nos.
5,263,480 (Wernicke et al.) and 5,188,104 (Wernicke et al.) are
generally directed to treatment of eating disorders with vagus
nerve stimulation using an implantable neurocybernetic prosthesis
(NCP), which is a "cardiac pacemaker-like" device. There is no
disclosure for vagal blocking.
[0030] U.S. Pat. No. 5,540,730 (Terry et al.) is generally directed
to treating motility disorders with vagus nerve stimulation using
an implantable neurocybernetic prosthesis (NCP), which is a
"cardiac pacemaker-like" device.
[0031] U.S. Pat. No. 6,553,263B1 (Meadows et al.) is generally
directed to an implantable pulse generator system for spinal cord
stimulation, which includes a rechargeable battery. In the Meadows
'263 patent there is no disclosure or suggestion for combing a
stimulus-receiver module to an implantable pulse generator (I PG)
for use with an external stimulator, for providing modulating
pulses to sympathetic nerve(s), as in the applicant's
disclosure.
[0032] U.S. Pat. No. 6,505,077 B1 (Kast et al.) is directed to
electrical connection for external recharging coil. In the Kast
'077 disclosure, a magnetic shield is required between the
externalized coil and the pulse generator case. In one embodiment
of the applicant's disclosure, the externalized coil is wrapped
around the pulse generator case, without requiring a magnetic
shield.
[0033] U.S. Pat. No. 6,600,954 B2 (Cohen et al.) is generally
directed to selectively blocking propagation of body-generated
action potentials particularly useful for pain control.
[0034] U.S. Pat. No. 6,684,105 B2 (Cohen et al.) is generally
directed to an apparatus for unidirectional nerve stimulation.
[0035] U.S. Pat. No. 6,611,715 B1 (Boveja) is generally directed to
a system and method to provide therapy for obesity and compulsive
eating disorders using an implantable lead-receiver and an external
stimulator.
SUMMARY OF THE INVENTION
[0036] The method and system of the current invention overcomes
many shortcomings of the prior art by providing a system for
neuromodulation with extended power source either in the form of
rechargeable battery, or by utilizing an external stimulator in
conjunction with an implanted pulse generator device, to provide
therapy for obesity, motility disorders, eating disorders, inducing
weight loss, FGIDs, gastroparesis, gastro-esophageal reflex disease
(GERD), pancreatitis, and ileus.
[0037] Accordingly, in one aspect of the invention, electrical
pulses are provided utilizing a rechargeable implantable pulse
generator for nerve blocking, with or without selective electrical
stimulation of vagus nerve(s) or its branches or part thereof for
treating obesity and other GI disorders.
[0038] In another aspect of the invention, the electrical pulses
are provided for at least one of afferent block, efferent block, or
organ block.
[0039] In another aspect of the invention, the nerve blocking
comprises at least one from a group consisting of: DC or anodal
block, Wedenski block, and Collision block.
[0040] In another aspect of the invention, a coil used in
recharging said pulse generator is around the implantable pulse
generator case, and in a silicone enclosure.
[0041] In another aspect of the invention, the rechargeable
implanted pulse generator comprises two feedthroughs.
[0042] In another aspect of the invention, the rechargeable
implanted pulse generator comprises only one feed-through for
externalizing the recharge coil.
[0043] In another aspect of the invention, the implantable
rechargeable pulse generator comprises stimulus-receiver means such
that, the implantable rechargeable pulse generator can function in
conjunction with an external stimulator, to provide nerve blocking
with or without selective electrical stimulation of vagus nerve(s)
or its branches or part thereof.
[0044] In another aspect of the invention, the rechargeable battery
comprises at least one of lithium-ion, lithium-ion polymer
batteries.
[0045] In another aspect of the invention, the external programmer
or the external stimulator comprises networking capabilities for
remote communications over a wide area network for remote
interrogation and/or remote programming.
[0046] In yet another aspect of the invention, the implanted lead
comprises at least two electrode(s) which are made of a material
selected from the group consisting of platinum, platinum/iridium
alloy, platinum/iridium alloy coated with titanium nitride, and
carbon.
[0047] This and other objects are provided by one or more of the
embodiments described below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0048] For the purpose of illustrating the invention, there are
shown in accompanying drawing forms which are presently preferred,
it being understood that the invention is not intended to be
limited to the precise arrangement and instrumentalities shown.
[0049] FIG. 1 is a diagram depicting vagal nerves in a patient.
[0050] FIG. 2 is a diagram showing vagal nerve innervation to the
viceral organs.
[0051] FIG. 3 is a schematic diagram showing the relationship of
meals and satiety signals.
[0052] FIG. 4 is a schematic diagram showing impulses traveling via
the vagus nerve in response to gastric distention and CCK
release.
[0053] FIG. 5 is a diagram depicting two-way communication between
the gut and central nervous system (CNS).
[0054] FIG. 6 is a diagram showing conduction of nerve impulses in
both afferent and efferent direction with artificial electrical
stimulation.
[0055] FIG. 7 is a diagram depicting blocking in the afferent
direction, but conducting in the efferent direction with electrical
stimulation.
[0056] FIG. 8 is a diagram depicting electrical stimulation with
conduction in the afferent direction and blocking in the efferent
direction.
[0057] FIG. 9 is a diagram depicting electrical stimulation with
conduction in the afferent direction and selective organ blocking
in the efferent direction.
[0058] FIG. 10 is a diagram depicting electrical stimulation with
conduction in the efferent direction and selective organ blocking
in the afferent direction.
[0059] FIG. 11 is a diagram of the structure of a nerve.
[0060] FIG. 12 is a diagram showing different types of nerve
fibers.
[0061] FIG. 13 is a schematic illustration of electrical circuit
model of nerve cell membrane.
[0062] FIG. 14 is an illustration of propagation of action
potential in nerve cell membrane.
[0063] FIG. 15 is an illustration showing propagation of action
potential along a myelinated axon and non-myelinated axon.
[0064] FIG. 16 is a diagram showing recordings of compound action
potentials.
[0065] FIG. 17 is a schematic diagram of brain showing afferent and
efferent pathways.
[0066] FIG. 18 is a diagram of implanted components of
stimulation/blocking system with multiple electrodes around
anterior and posterior vagal nerves.
[0067] FIG. 19A is a diagram showing the implanted components
(rechargeable implantable pulse generator), and an external
stimulator coupled to implanted stimulus-receiver.
[0068] FIG. 19B is a diagram showing placement of the external
(primary) coil in relation of the implanted stimulus-receiver.
[0069] FIG. 20 is a simplified general block diagram of an
implantable pulse generator.
[0070] FIG. 21A shows energy density of different types of
batteries.
[0071] FIG. 21B shows discharge curves for different types of
batteries.
[0072] FIG. 22 shows a block diagram of an implantable stimulator
which can be used as a stimulus-receiver or an implanted pulse
generator with rechargeable battery.
[0073] FIG. 23 is a block diagram highlighting battery charging
circuit of the implantable stimulator of FIG. 22.
[0074] FIG. 24 is a schematic diagram highlighting
stimulus-receiver portion of implanted stimulator of one
embodiment.
[0075] FIG. 25 depicts externalizing recharge and telemetry coil
from the titanium case.
[0076] FIG. 26A depicts coil around the titanium case with two
feedthroughs for a bipolar configuration.
[0077] FIG. 26B depicts coil around the titanium case with one
feedthrough for a unipolar configuration.
[0078] FIG. 26C depicts two feedthroughs for the external coil
which are common with the feedthroughs for the lead terminal.
[0079] FIG. 26D depicts one feedthrough for the external coil which
is common to the feedthrough for the lead terminal.
[0080] FIGS. 27A and 27B depict recharge coil on the titanium case
with a magnetic shield in-between.
[0081] FIG. 28 shows a rechargeable implantable pulse generator in
block diagram form.
[0082] FIG. 29 depicts in block diagram form, the implanted and
external components of an implanted rechargable system.
[0083] FIG. 30 depicts the alignment function of rechargable
implantable pulse generator.
[0084] FIG. 31 is a block diagram of the external recharger.
[0085] FIG. 32A is a schematic diagram of an implantable lead with
three electrodes.
[0086] FIG. 32B is a schematic diagram of an implantable lead with
multiple electrodes.
[0087] FIG. 32C is a schematic diagram of an implantable lead with
two electrodes.
[0088] FIG. 33 is a schematic diagram of the pulse generator and
two-way communication through a server.
[0089] FIG. 34 is a diagram depicting wireless remote interrogation
and programming of the external pulse generator.
[0090] FIG. 35 is a schematic diagram of the wireless protocol.
[0091] FIG. 36 is a simplified block diagram of the networking
interface board.
[0092] FIGS. 37A and 37B are simplified diagrams showing
communication of modified PDA/phone with an external stimulator via
a cellular tower/base station.
DESCRIPTION OF THE INVENTION
[0093] To provide vagal blocking and/or vagal stimulation therapy
to a patient, blocking and stimulation electrodes are implanted at
the appropriate sites. In one preferred embodiment, without
limitation, multiple electrodes comprising both blocking and
stimulation electrodes are placed in a band. As shown in
conjunction with FIG. 18, the band comprising multiple electrodes
is wrapped around the esophagus, close to the junction of esophagus
and the stomach 5 (just below the diaphragm). Alternatively, the
individual electrodes do not have to be in a band, and may be
individual electrodes, connected to the body of the lead via
insulated conductors (shown in FIG. 32B). In such a case, the
portion of the electrode contacting the nerve tissue would be
exposed and the rest of the electrode being insulated with a
non-conductive material such as silicone or polyurethane. Such
electrodes are well known in the art.
[0094] The electrodes may be implanted using laproscopic surgery or
alternatively a surgical exposure may be made for implantation of
the electrodes at the appropriate site to be stimulated and/or
blocked. After placing the electrodes, the terminal portion of the
lead is tunneled to a subcutaneous site where the electronics
package is to be implanted. The terminal end of the lead is
connected to the rechargeable implantable pulse generator. The
patient is surgically closed in layers, and electrical pulse
delivery can begin once the patient has fully recovered from the
surgery.
[0095] In the method and system of this invention, stimulation
without block may be provided. Additionally, stimulation with
selective block may be provided. Furthermore, block alone (without
stimulation) may be provided, which would be functionally
equivalent to reversible vagotomy.
[0096] Blocking of nerve impulses, unidirectional blocking, and
selective blocking of nerve impulses is well known in the
scientific literature. Some of the general literature is listed
below and is incorporated herein by reference. (a) "Generation of
unidirectionally propagating action potentials using a monopolar
electrode cuff", Annals of Biomedical Engineering, volume 14, pp.
437-450, By Ira J. Ungar et al. (b) "An asymmetric two electrode
cuff for generation of unidirectionally propagated action
potentials", IEEE Transactions on Biomedical Engineering, volume
BME-33, No. 6, June 1986, By James D. Sweeney, et al. (c) A spiral
nerve cuff electrode for peripheral nerve stimulation, IEEE
Transactions on Biomedical Engineering, volume 35, No. 11, November
1988, By Gregory G. Naples. et al. (d) "A nerve cuff technique for
selective excitation of peripheral nerve trunk regions, IEEE
Transactions on Biomedical Engineering, volume 37, No. 7, July
1990, By James D. Sweeney, et al. (e) "Generation of
unidirectionally propagated action potentials in a peripheral nerve
by brief stimuli", Science, volume 206 pp. 1311-1312, Dec. 14,
1979, By Van Den Honert et al. (f "A technique for collision block
of perpheral nerve: Frequency dependence" IEEE Transactions on
Biomedical Engineering, MP-12, volume 28, pp. 379-382, 1981, By Van
Den Honert et al. (g) "A nerve cuff design for the selective
activation and blocking of myelinated nerve fibers" Ann. Conf. of
the IEEE Engineering in Medicine and Biology Soc., volume 13, No.
2, p 906, 1991, By D. M Fitzpatrick et al. (h) "Orderly recruitment
of motoneurons in an acute rabbit model", "Ann. Conf. of the IEEE
Engineering in Medicine and Biology Soc., volume 20, No. 5, page
2564, 1998, By N. J. M. Rijkhof, et al. (i) "Orderly stimulation of
skeletal muscle motor units with tripolar nerve cuff electrode",
IEEE Transactions on Biomedical Engineering, volume 36, No. 8, pp.
836,1989, By R. Bratta. (j) M. Devor, "Pain Networks", Handbook of
Brand Theory and Neural Networks, Ed. M. A. Arbib, MIT Press, page
698, 1998.
[0097] Blocking can be generally divided into 3 categories: (a) DC
or anodal block, (b) Wedenski Block, and (c) Collision block. In
anodal block there is a steady potential which is applied to the
nerve causing a reversible and selective block. In Wedenski Block
the nerve is stimulated at a high rate causing the rapid depletion
of the neurotransmitter. In collision blocking, unidirectional
action potentials are generated anti-dromically. The maximal
frequency for complete block is the reciprocal of the refractory
period plus the transit time, i.e. typically less than a few
hundred hertz. The use of any of these blocking techniques can be
applied for the practice of this invention, and all are considered
within the scope of this invention.
[0098] FIGS. 19A and 19B depict the implantable components of the
system. A rechargeable implantable pulse generator 391R is
connected to the lead 40 for delivering pulses via multiple
electrodes in contact with nerve tissue. The selective blocking
and/or stimulation to the vagal nerve tissue 54 can be performed by
"pre-determined" programs stored in the memory, or by "customized"
programs where the electrical parameters are selectively programmed
for specific therapy to the individual patient. The electrical
parameters which can be individually programmed, include variables
such as pulse amplitude, pulse width, frequency of stimulation,
type of pulse (e.g. blocking pulses may be sinusoidal), stimulation
on-time, and stimulation off-time. Table two below defines the
approximate range of parameters,
2TABLE 2 Electrical parameter range delivered to the nerve for
stimulation and/or blocking PARAMER RANGE Pulse Amplitude 0.1
Volt-10 Volts Pulse width 20 .mu.S-5 mSec. Stim. Frequency 5 Hz-200
Hz Freq. for blocking DC to 5,000 Hz On-time 5 Secs-24 hours
Off-time 5 Secs-24 hours
[0099] The parameters in Table 2 are the electrical signals
delivered to the nerve tissue via the two stimulation electrodes
61,62 (or blocking electrodes) at the nerve tissue 54.
[0100] Shown in conjunction with FIG. 20, is an overall schematic
of a general implantable pulse generator system to deliver
electrical pulses for modulating the vagus nerve(s) (selective
stimulation and/or blocking) and providing therapy. The implantable
pulse generator unit 391 is a microprocessor based device, where
the entire circuitry is encased in a hermetically sealed titanium
can. As shown in the overall block diagram, the logic & control
unit 398 provides the proper timing for the output circuitry 385 to
generate electrical pulses that are delivered to a pair of
electrodes via a lead 40. Timing is provided by oscillator 393. The
pair of electrodes to which the stimulation energy is delivered is
switchable. Programming of the implantable pulse generator (IPG)
391 is done via an external programmer 85. Once programmed via an
external programmer 85, the implanted pulse generator 391 provides
appropriate electrical blocking and/or stimulation pulses to the
vagal nerve(s) 54 via the blocking/stimulating electrodes
61,62,63.
[0101] Because of the high energy requirements for the pulses
required for blocking and/or selective stimulation of vagal nerve
tissue 54, there is a real need for power sources that will provide
an acceptable service life under conditions of continuous delivery
of high frequency pulses. FIG. 21A shows a graph of the energy
density of several commonly used battery technologies. Lithium
batteries have by far the highest energy density of commonly
available batteries. Also, a lithium battery maintains a nearly
constant voltage during discharge. This is shown in conjunction
with FIG. 21B, which is normalized to the performance of the
lithium battery. Lithium-ion batteries also have a long cycle life,
and no memory effect. However, Lithium-ion batteries are not as
tolerant to overcharging and overdischarging. One of the most
recent development in rechargable battery technology is the
Lithium-ion polymer battery. Recently the major battery
manufacturers (Sony, Panasonic, Sanyo) have announced plans for
Lithium-ion polymer battery production.
[0102] For preferred method of the current invention, two
embodiments of implantable pulse generators may be used. Both
embodiments comprise re-chargeable power sources, such as
Lithium-ion polymer battery.
[0103] In one embodiment of this invention, the implanted
stimulator comprises a stimulus-receiver module and a pulse
generator module. Advantageously, this embodiment provides an ideal
power source, since the power source can be an external stimulator
in conjunction with an implanted stimulus-receiver, or the power
source can be from the implanted rechargable battery 740. Shown in
conjunction with FIG. 22 is a simplified overall block diagram of
this embodiment. A coil 48C which is external to the titanium case
may be used both as a secondary of a stimulus-receiver, or may also
be used as the forward and back telemetry coil. The coil 48C may be
externalized at the header portion 79C of the implanted device, and
may be wrapped around the titanium case, eliminating the need for a
magnetic shield. In this case, the coil is encased in the same
material as the header 79C. Alternatively, the coil may be
positioned on the titanium case, with a magnetic shield.
[0104] In this embodiment, as disclosed in FIG. 22, the IPG
circuitry within the titanium case is used for all stimulation
pulses whether the energy source is the internal rechargeable
battery 740 or an external power source. The external device serves
as a source of energy, and as a programmer that sends telemetry to
the IPG. For programming, the energy is sent as high frequency sine
waves with superimposed telemetry wave driving the external coil
46C. The telemetry is passed through coupling capacitor 727 to the
IPG's telemetry circuit 742. For pulse delivery using external
power source, the stimulus-receiver portion will receive the energy
coupled to the implanted coil 48C and, using the power conditioning
circuit 726, rectify it to produce DC, filter and regulate the DC,
and couple it to the IPG's voltage regulator 738 section so that
the IPG can run from the externally supplied energy rather than the
implanted battery 740.
[0105] The system provides a power sense circuit 728 that senses
the presence of external power communicated with the power control
730, when adequate and stable power is available from an external
source. The power control circuit controls a switch 736 that
selects either implanted rechargeable battery power 740 or
conditioned external power from 726. The logic and control section
732 and memory 744 includes the IPG's microcontroller,
pre-programmed instructions, and stored changeable parameters.
Using input for the telemetry circuit 742 and power control 730,
this section controls the output circuit 734 that generates the
output pulses.
[0106] Shown in conjunction with FIG. 23, this embodiment of the
invention is practiced with a rechargeable battery 740. This
circuit is energized when external power is available. It senses
the charge state of the battery and provides appropriate charge
current to safely recharge the battery without overcharging.
Recharging circuitry is described later.
[0107] The stimulus-receiver portion of the circuitry is shown in
conjunction with FIG. 24. Capacitor C1 (729) makes the combination
of C1 and L1 sensitive to the resonant frequency and less sensitive
to other frequencies, and energy from an external (primary) coil
46C is inductively transferred to the implanted unit via the
secondary coil 48C. The AC signal is rectified to DC via diode 731,
and filtered via capacitor 733. A regulator 735 set the output
voltage and limits it to a value just above the maximum IPG cell
voltage. The output capacitor C4 (737), typically a tantalum
capacitor with a value of 100 micro-Farads or greater, stores
charge so that the circuit can supply the IPG with high values of
current for a short time duration with minimal voltage change
during a pulse while the current draw from the external source
remains relatively constant. Also shown in conjunction with FIGS.
23 and 24, a capacitor C3 (727) couples signals for forward and
back telemetry.
[0108] In another embodiment, existing implantable pulse generators
can be modified to incorporate rechargeable batteries. As shown in
conjunction with FIG. 25, in both embodiments, the coil is
externalized from the titanium case 57. The RF pulses transmitted
via coil 46 and received via subcutaneous coil 48A are rectified
via a diode bridge. These DC pulses are processed and the resulting
current applied to recharge the battery 694/740 in the implanted
pulse generator. In one embodiment the coil 48 may be externalized
at the header portion 79C of the implanted device, and may be
wrapped around the titanium case, as shown in FIGS. 26A and 26B.
Shown in FIG. 26A is a bipolar configuration which requires two
feedthroughs 76,77. Advantageously, as shown in FIG. 26B unipolar
configuration may also be used which requires only one feedthrough
75. The other end is electronically connected to the case. In both
cases, the coil is encased in the same material as the header 79.
Advantageously, as shown in conjunction with FIGS. 26C and 26D, the
feedthrough for the coil can be combined with the feedthrough for
the lead terminal. This can be applied both for bipolar and
unipolar configurations.
[0109] In one embodiment, the coil may be positioned on the
titanium case as shown in conjunction with FIGS. 27A and 27B. FIG.
27A shows a diagram of the finished implantable stimulator 391R of
one embodiment. FIG. 27B shows the pulse generator with some of the
components used in assembly in an exploded view. These components
include a coil cover 13, the secondary coil 48 and associated
components, a magnetic shield 9, and a coil assembly carrier 11.
The coil assembly carrier 11 has at least one positioning detail 80
located between the coil assembly and the feed through for
positioning the electrical connection. The positioning detail 80
secures the electrical connection in this embodiment.
[0110] A schematic diagram of the implanted pulse generator (IPG
391R), with re-chargeable battery 694 of one preferred embodiment
of this invention, is shown in conjunction with FIG. 28. The IPG
391R includes logic and control circuitry 673 connected to memory
circuitry 691. The operating program and stimulation parameters are
typically stored within the memory 691 via forward telemetry.
Blocking/stimulation pulses are provided to the nerve tissue 54 via
output circuitry 677 controlled by the microcontroller.
[0111] The operating power for the IPG 391R is derived from a
rechargeable power source 694. The rechargeable power source 694
comprises a rechargeable lithium-ion or lithium-ion polymer
battery. Recharging occurs inductively from an external charger to
an implanted coil 48B underneath the skin 60. The rechargeable
battery 694 may be recharged repeatedly as needed. Additionally,
the IPG 391R is able to monitor and telemeter the status of its
rechargeable battery 691 each time a communication link is
established with the external programmer 85.
[0112] Much of the circuitry included within the IPG 391R may be
realized on a single application specific integrated circuit
(ASIC). This allows the overall size of the IPG 391R to be quite
small, and readily housed within a suitable hermetically-sealed
case. The IPG case is preferably made from titanium and is shaped
in a rounded case.
[0113] Shown in conjunction with FIG. 29 are the recharging
elements of the invention. The recharging system uses a portable
external charger to couple energy into the power source of the IPG
391R. The DC-to-AC conversion circuitry 696 of the recharger
receives energy from a battery 672 in the recharger. A charger base
station 680 and conventional AC power line may also be used. The AC
signals amplified via power amplifier 674 are inductively coupled
between an external coil 46B and an implanted coil 48B located
subcutaneously with the implanted pulse generator (IPG) 391R. The
AC signal received via implanted coil 48B is rectified 686 to a DC
signal which is used for recharging the rechargable battery 694 of
the IPG, through a charge controller IC 682. Additional circuitry
within the IPG 391R includes, battery protection IC 688 which
controls a FET switch 690 to make sure that the rechargable battery
694 is charged at the proper rate, and is not overcharged. The
battery protection IC 688 can be an off-the-shelf IC available from
Motorola (part no. MC 33349N-3R1). This IC monitors the voltage and
current of the implanted rechargable battery 694 to ensure safe
operation. If the battery voltage rises above a safe maximum
voltage, the battery protection IC 688 opens charge enabling FET
switches 690, and prevents further charging. A fuse 692 acts as an
additional safeguard, and disconnects the battery 694 if the
battery charging current exceeds a safe level. As also shown in
FIG. 29, charge completion detection is achieved by a
back-telemetry transmitter 684, which modulates the secondary load
by changing the full-wave rectifier into a half-wave
rectifier/voltage clamp. This modulation is in turn, sensed by the
charger as a change in the coil voltage due to the change in the
reflected impedance. When detected through a back telemetry
receiver 676, either an audible alarm is generated or a LED is
turned on.
[0114] A simplified block diagram of charge completion and
misalignment detection circuitry is shown in conjunction with FIG.
30. As shown, a switch regulator 686 operates as either a full-wave
rectifier circuit or a half-wave rectifier circuit as controlled by
a control signal (CS) generated by charging and protection
circuitry 698. The energy induced in implanted coil 48B (from
external coil 46B) passes through the switch rectifier 686 and
charging and protection circuitry 698 to the implanted rechargable
battery 694. As the implanted battery 694 continues to be charged,
the charging and protection circuitry 698 continuously monitors the
charge current and battery voltage. When the charge current and
battery voltage reach a predetermined level, the charging and
protection circuitry 698 triggers a control signal. This control
signal causes the switch rectifier 686 to switch to half-wave
rectifier operation. When this change happens, the voltage sensed
by voltage detector 702 causes the alignment indicator 706 to be
activated. This indicator 706 may be an audible sound or a flashing
LED type of indicator.
[0115] The indicator 706 may similarly be used as a misalignment
indicator. In normal operation, when coils 46B (external) and 48B
(implanted) are properly aligned, the voltage V.sub.s sensed by
voltage detector 704 is at a minimum level because maximum energy
transfer is taking place. If and when the coils 46B and 48B become
misaligned, then less than a maximum energy transfer occurs, and
the voltage V.sub.s sensed by detection circuit 704 increases
significantly. If the voltage V.sub.s reaches a predetermined
level, alignment indicator 706 is activated via an audible speaker
and/or LEDs for visual feedback. After adjustment, when an optimum
energy transfer condition is established, causing V.sub.s to
decrease below the predetermined threshold level, the alignment
indicator 706 is turned off.
[0116] The elements of the external recharger are shown as a block
diagram in conjunction with FIG. 31. The charger base station 680
receives its energy from a standard power outlet 714, which is then
converted to 5 volts DC by a AC-to-DC transformer 712. When the
recharger is placed in a charger base station 680, the rechargable
battery 672 of the recharger is fully recharged in a few hours and
is able to recharge the battery 694 of the IPG 391R. If the battery
672 of the external recharger falls below a prescribed limit of 2.5
volt DC, the battery 672 is trickle charged until the voltage is
above the prescribed limit, and then at that point resumes a normal
charging process.
[0117] As also shown in FIG. 31, a battery protection circuit 718
monitors the voltage condition, and disconnects the battery 672
through one of the FET switches 716, 720 if a fault occurs until a
normal condition returns. A fuse 724 will disconnect the battery
672 should the charging or discharging current exceed a prescribed
amount.
[0118] Referring now to FIG. 32A, the implanted lead component of
the system is similar to cardiac pacemaker leads, except for distal
portion (or electrode end) of the lead. This figure depicts a lead
with tripolar electrodes 62,61,63 for stimulation and/or blocking.
FIG. 32B shows a lead with multiple pairs of electrodes (63, 62,
61). Different electrodes or electrode pairs are used for blocking
or for stimulation, as directed by logic and control unit 673 of
rechargeable implantable pulse generator 691R. An alternative
embodiment with a pair of electrodes 61, 62 is also shown in FIG.
32C. The lead terminal preferably is linear bipolar, even though it
can be bifurcated, and plug(s) into the cavity of the pulse
generator means. The lead body 59 insulation may be constructed of
medical grade silicone, silicone reinforced with
polytetrafluoro-ethylene (PTFE), or polyurethane. The electrodes
61,62,63 for stimulating/blocking the vagus nerve 54 may either
wrap around the nerve or may be adapted to be in contact with
tissue to be blocked/stimulated. These stimulating electrodes may
be made of pure platinum, platinum/Iridium alloy or
platinum/iridium coated with titanium nitride. The conductor
connecting the terminal to the electrodes 61,62 is made of an alloy
of nickel-cobalt. The implanted lead design variables are also
summarized in table four below.
3TABLE 4 Lead design variables Proximal Distal End End Conductor
(connecting Lead body- proximal Lead Insulation and distal
Electrode - Electrode - Terminal Materials Lead-Coating ends)
Material Type Linear Polyurethane Antimicrobial Alloy of Pure
Wrap-around bipolar coating Nickel- Platinum electrodes Cobalt
Bifurcated Silicone Anti- Platinum- Standard Ball Inflammatory
Iridium and Ring coating (Pt/Ir) Alloy electrodes Silicone with
Lubricious Pt/Ir coated Steroid Polytetrafluoroethylene coating
with Titanium eluting (PTFE) Nitride Carbon
[0119] Once the lead is fabricated, coating such as anti-microbial,
anti-inflammatory, or lubricious coating may be applied to the body
of the lead.
Telemetry Module
[0120] Shown in conjunction with FIG. 33, in one embodiment of the
invention the external stimulator 42 and/or programmer 85 may
comprise two-way wireless communication capabilities with a remote
server, using a communication protocol such as the wireless
application protocol (WAP). The purpose of the telemetry module is
to enable the physician to remotely, via the wireless medium change
the programs, activate, or disengage programs. Additionally,
schedules of therapy programs, can be remotely transmitted and
verified. Advantageously, the physician is thus able to remotely
control the stimulation therapy.
[0121] FIG. 34 is a simplified schematic showing the communication
aspects between the external stimulator 42 and or programmer 85,
and the remote hand-held computer. A desktop or laptop computer can
be a server 130 which is situated remotely, perhaps at a
health-care provider's facility or a hospital. The data can be
viewed at this facility or reviewed remotely by medical personnel
on a wireless internet supported hand-held device 140, which could
be a personal data assistant (PDA), for example, a "palm-pilot"
from PALM corp. (Santa Clara, Calif.), a "Visor" from Handspring
Corp. (Mountain view, CA) or on a personal computer (PC) available
from numerous vendors or a cell phone or a handheld device being a
combination thereof. The physician or appropriate medical
personnel, is able to interrogate the external stimulator 42 device
and know what the device is currently programmed to, as well as,
get a graphical display of the pulse train. The wireless
communication with the remote server 130 and hand-held device
(wireless internet supported) 140 can be achieved in all
geographical locations within and outside the United States (US)
that provides cell phone voice and data communication service. The
pulse generation parameter data can also be viewed on the handheld
devices 140.
[0122] The telecommunications component of this invention uses
Wireless Application Protocol (WAP). WAP is a set of communication
protocols standardizing Internet access for wireless devices.
Previously, manufacturers used different technologies to get
Internet on hand-held devices. With WAP, devices and services
inter-operate. WAP promotes convergence of wireless data and the
Internet. The WAP Layers are Wireless Application Environment
(WAE), Wireless Session Layer (WSL), Wireless Transport Layer
Security (WTLS) and Wireless Transport Layer (WTP).
[0123] The WAP programming model, which is heavily based on the
existing Internet programming model, is shown schematically in FIG.
35. Introducing a gateway function provides a mechanism for
optimizing and extending this model to match the characteristics of
the wireless environment. Over-the-air traffic is minimized by
binary encoding/decoding of Web pages and readapting the Internet
Protocol stack to accommodate the unique characteristics of a
wireless medium such as call drops. Such features are facilitated
with WAP.
[0124] The key components of the WAP technology, as shown in FIG.
35, includes 1) Wireless Mark-up Language (WML) 400 which
incorporates the concept of cards and decks, where a card is a
single unit of interaction with the user. A service constitutes a
number of cards collected in a deck. A card can be displayed on a
small screen. WML supported Web pages reside on traditional Web
servers. 2) WML Script which is a scripting language, enables
application modules or applets to be dynamically transmitted to the
client device and allows the user interaction with these applets.
3) Microbrowser, which is a lightweight application resident on the
wireless terminal that controls the user interface and interprets
the WML/WMLScript content. 4) A lightweight protocol stack 402
which minimizes bandwidth requirements, guaranteeing that a broad
range of wireless networks can run WAP applications. The protocol
stack of WAP can comprise a set of protocols for the transport
(WTP), session (WSP), and security (WTLS) layers. WSP is binary
encoded and able to support header caching, thereby economizing on
bandwidth requirements. WSP also compensates for high latency by
allowing requests and responses to be handles asynchronously,
sending before receiving the response to an earlier request. For
lost data segments, perhaps due to fading or lack of coverage, WTP
only retransmits lost segments using selective retransmission,
thereby compensating for a less stable connection in wireless. The
above mentioned features are industry standards adopted for
wireless applications, and well known to those skilled in the
art.
[0125] The presently preferred embodiment utilizes WAP, because WAP
has the following advantages, 1) WAP protocol uses less than
one-half the number of packets that the standard HTTP or TCP/IP
Internet stack uses to deliver the same content. 2) Addressing the
limited resources of the terminal, the browser, and the lightweight
protocol stack are designed to make small claims on CPU and ROM. 3)
Binary encoding of WML and SMLScript helps keep the RAM as small as
possible. And, 4) Keeping the bearer utilization low takes account
of the limited battery power of the terminal.
[0126] In this embodiment two modes of communication are possible.
In the first, the server initiates an upload of the actual
parameters being applied to the patient, receives these from the
stimulator, and stores these in its memory, accessible to the
authorized user as a dedicated content driven web page. The web
page is managed with adequate security and password protection. The
physician or authorized user can make alterations to the actual
parameters, as available on the server, and then initiate a
communication session with the stimulator device to download these
parameters.
[0127] The physician is also able to set up long-term schedules of
stimulation therapy for their patient population, through wireless
communication with the server. The server in turn communicates
these programs to the neurostimulator. Each schedule is securely
maintained on the server, and is editable by the physician and can
get uploaded to the patient's stimulator device at a scheduled
time. Thus, therapy can be customized for each individual patient.
Each device issued to a patient has a unique identification key in
order to guarantee secure communication between the wireless server
130 and stimulator device 42.
[0128] In this embodiment, two modes of communication are possible.
In the first, the server initiates an upload of the actual
parameters being applied to the patient, receives these from the
stimulator, and stores these in its memory, accessible to the
authorized user as a dedicated content driven web page. The
physician or authorized user can make alterations to the actual
parameters, as available on the server, and then initiate a
communication session with the stimulator device to download these
parameters.
[0129] Shown in conjunction with FIG. 36, in one embodiment, the
external stimulator 42 and/or the programmer 85 may also be
networked to a central collaboration computer 286 as well as other
devices such as a remote computer 294, PDA 140, phone 141,
physician computer 143. The interface unit 292 in this embodiment
communicates with the central collaborative network 290 via
land-lines such as cable modem or wirelessly via the internet. A
central computer 286 which has sufficient computing power and
storage capability to collect and process large amounts of data,
contains information regarding device history and serial number,
and is in communication with the network 290. Communication over
collaboration network 290 may be effected by way of a TCP/IP
connection, particularly one using the internet, as well as a PSTN,
DSL, cable modem, LAN, WAN or a direct dial-up connection.
[0130] The standard components of interface unit shown in block 292
are processor 305, storage 310, memory 308, transmitter/receiver
306, and a communication device such as network interface card or
modem 312. In the preferred embodiment these components are
embedded in the external stimulator 42 and can also be embedded in
the programmer 85. These can be connected to the network 290
through appropriate security measures (Firewall) 293.
[0131] Another type of remote unit that may be accessed via central
collaborative network 290 is remote computer 294. This remote
computer 294 may be used by an appropriate attending physician to
instruct or interact with interface unit 292, for example,
instructing interface unit 292 to send instruction downloaded from
central computer 286 to remote implanted unit.
[0132] Shown in conjunction with FIG. 37A the physician's remote
communication's module is a Modified PDA/Phone 140 in this
embodiment. The Modified PDA/Phone 140 is a microprocessor based
device as shown in a simplified block diagram in FIGS. 37A and 37B.
The PDA/Phone 140 is configured to accept PCM/CIA cards specially
configured to fulfill the role of communication module 292 of the
present invention. The Modified PDA/Phone 140 may operate under any
of the useful software including Microsoft Window's based, Linux,
Palm OS, Java OS, SYMBIAN, or the like.
[0133] The telemetry module 362 comprises an RF telemetry antenna
142 coupled to a telemetry transceiver and antenna driver circuit
board which includes a telemetry transmitter and telemetry
receiver. The telemetry transmitter and receiver are coupled to
control circuitry and registers, operated under the control of
microprocessor 364. Similarly, within stimulator a telemetry
antenna 142 is coupled to a telemetry transceiver comprising RF
telemetry transmitter and receiver circuit. This circuit is coupled
to control circuitry and registers operated under the control of
microcomputer circuit.
[0134] With reference to the telecommunications aspects of the
invention, the communication and data exchange between Modified
PDA/Phone 140 and external stimulator 42 operates on commercially
available frequency bands. The 2.4-to-2.4853 GHz bands or 5.15 and
5.825 GHz, are the two unlicensed areas of the spectrum, and set
aside for industrial, scientific, and medical (ISM) uses. Most of
the technology today including this invention, use either the 2.4
or 5 GHz radio bands and spread-spectrum technology.
[0135] The telecommunications technology, especially the wireless
internet technology, which this invention utilizes in one
embodiment, is constantly improving and evolving at a rapid pace,
due to advances in RF and chip technology as well as software
development. Therefore, one of the intents of this invention is to
utilize "state of the art" technology available for data
communication between Modified PDA/Phone 140 and external
stimulator 42. The intent of this invention is to use 3G technology
for wireless communication and data exchange, even though in some
cases 2.5G is being used currently.
[0136] For the system of the current invention, the use of any of
the "3G" technologies for communication for the Modified PDA/Phone
140, is considered within the scope of the invention. Further, it
will be evident to one of ordinary skill in the art that as future
4G systems, which will include new technologies such as improved
modulation and smart antennas, can be easily incorporated into the
system and method of current invention, and are also considered
within the scope of the invention.
* * * * *