FIELD OF INVENTION
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.
- Background of Obesity and Relation to Vagus Nerve
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.
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.
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.
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.
The vagus nerve (which is the 10th 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.
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.
- Vagal Blocking and/or Stimulation
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.
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.
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.
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.
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.
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.
- Background of Neuromodulation
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.
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.
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 μm 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 μm in diameter and are unmyelinated.
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.
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.
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.
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 ΔV, 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.
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 (rm), membrane capacitance (cm), and axonal resistance (ra).
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+ channels have returned to their resting state by the voltage activated K+ 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.
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.
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 (μs), 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 μs) 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.
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,
| ||TABLE 1 |
| || |
| || |
| || ||Conduction ||Fiber || |
| ||Fiber ||Velocity ||Diameter |
| ||Type ||(m/sec) ||(μm) ||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 |
| || |
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 10th 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).
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).
- PRIOR ART
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 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.
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.
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.
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.
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.
U.S. Pat. No. 6,684,105 B2 (Cohen et al.) is generally directed to an apparatus for unidirectional nerve stimulation.
- SUMMARY OF THE INVENTION
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.
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.
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.
In another aspect of the invention, the electrical pulses are provided for at least one of afferent block, efferent block, or organ block.
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.
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.
In another aspect of the invention, the rechargeable implanted pulse generator comprises two feedthroughs.
In another aspect of the invention, the rechargeable implanted pulse generator comprises only one feed-through for externalizing the recharge coil.
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.
In another aspect of the invention, the rechargeable battery comprises at least one of lithium-ion, lithium-ion polymer batteries.
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.
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.
BRIEF DESCRIPTION OF THE DRAWINGS
This and other objects are provided by one or more of the embodiments described below.
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.
FIG. 1 is a diagram depicting vagal nerves in a patient.
FIG. 2 is a diagram showing vagal nerve innervation to the viceral organs.
FIG. 3 is a schematic diagram showing the relationship of meals and satiety signals.
FIG. 4 is a schematic diagram showing impulses traveling via the vagus nerve in response to gastric distention and CCK release.
FIG. 5 is a diagram depicting two-way communication between the gut and central nervous system (CNS).
FIG. 6 is a diagram showing conduction of nerve impulses in both afferent and efferent direction with artificial electrical stimulation.
FIG. 7 is a diagram depicting blocking in the afferent direction, but conducting in the efferent direction with electrical stimulation.
FIG. 8 is a diagram depicting electrical stimulation with conduction in the afferent direction and blocking in the efferent direction.
FIG. 9 is a diagram depicting electrical stimulation with conduction in the afferent direction and selective organ blocking in the efferent direction.
FIG. 10 is a diagram depicting electrical stimulation with conduction in the efferent direction and selective organ blocking in the afferent direction.
FIG. 11 is a diagram of the structure of a nerve.
FIG. 12 is a diagram showing different types of nerve fibers.
FIG. 13 is a schematic illustration of electrical circuit model of nerve cell membrane.
FIG. 14 is an illustration of propagation of action potential in nerve cell membrane.
FIG. 15 is an illustration showing propagation of action potential along a myelinated axon and non-myelinated axon.
FIG. 16 is a diagram showing recordings of compound action potentials.
FIG. 17 is a schematic diagram of brain showing afferent and efferent pathways.
FIG. 18 is a diagram of implanted components of stimulation/blocking system with multiple electrodes around anterior and posterior vagal nerves.
FIG. 19A is a diagram showing the implanted components (rechargeable implantable pulse generator), and an external stimulator coupled to implanted stimulus-receiver.
FIG. 19B is a diagram showing placement of the external (primary) coil in relation of the implanted stimulus-receiver.
FIG. 20 is a simplified general block diagram of an implantable pulse generator.
FIG. 21A shows energy density of different types of batteries.
FIG. 21B shows discharge curves for different types of batteries.
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.
FIG. 23 is a block diagram highlighting battery charging circuit of the implantable stimulator of FIG. 22.
FIG. 24 is a schematic diagram highlighting stimulus-receiver portion of implanted stimulator of one embodiment.
FIG. 25 depicts externalizing recharge and telemetry coil from the titanium case.
FIG. 26A depicts coil around the titanium case with two feedthroughs for a bipolar configuration.
FIG. 26B depicts coil around the titanium case with one feedthrough for a unipolar configuration.
FIG. 26C depicts two feedthroughs for the external coil which are common with the feedthroughs for the lead terminal.
FIG. 26D depicts one feedthrough for the external coil which is common to the feedthrough for the lead terminal.
FIGS. 27A and 27B depict recharge coil on the titanium case with a magnetic shield in-between.
FIG. 28 shows a rechargeable implantable pulse generator in block diagram form.
FIG. 29 depicts in block diagram form, the implanted and external components of an implanted rechargable system.
FIG. 30 depicts the alignment function of rechargable implantable pulse generator.
FIG. 31 is a block diagram of the external recharger.
FIG. 32A is a schematic diagram of an implantable lead with three electrodes.
FIG. 32B is a schematic diagram of an implantable lead with multiple electrodes.
FIG. 32C is a schematic diagram of an implantable lead with two electrodes.
FIG. 33 is a schematic diagram of the pulse generator and two-way communication through a server.
FIG. 34 is a diagram depicting wireless remote interrogation and programming of the external pulse generator.
FIG. 35 is a schematic diagram of the wireless protocol.
FIG. 36 is a simplified block diagram of the networking interface board.
DESCRIPTION OF THE INVENTION
FIGS. 37A and 37B are simplified diagrams showing communication of modified PDA/phone with an external stimulator via a cellular tower/base station.
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.
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.
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.
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.
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.
FIGS. 19A and 19B
depict the implantable components of the system. A rechargeable implantable pulse generator 391
R 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,
|TABLE 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 μS-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 |
| || |
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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 Vs 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 Vs sensed by detection circuit 704 increases significantly. If the voltage Vs 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 Vs to decrease below the predetermined threshold level, the alignment indicator 706 is turned off.
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.
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.
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
for stimulation and/or blocking. FIG. 32B
shows a lead with multiple pairs of electrodes (63
). 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 691
R. An alternative embodiment with a pair of electrodes 61
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
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
is made of an alloy of nickel-cobalt. The implanted lead design variables are also summarized in table four below.
|TABLE 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 |
- Telemetry Module
Once the lead is fabricated, coating such as anti-microbial, anti-inflammatory, or lubricious coating may be applied to the body of the lead.
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.
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.
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).
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.