FIELD OF INVENTION
This invention relates generally to electrical stimulation therapy for gastrointestinal (GI) disorders, more specifically to gastric myo-electrical pacing therapy for obesity and eating disorders with rechargeable implantable pulse generator.
BACKGROUND
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 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.
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.
This Application discloses a method and system for providing gastric myo-electric pulses to the stomach wall using an implanted gastric lead and a rechargeable implantable pulse generator (FIGS. 10 and 11). Such gastric pacing disrupts the normal gastric motility and provides therapy to an obese patient. Advantageously, such disruption of the normal gastric motility is reversible, unlike gastric bypass surgery. Details of such system and method are disclosed in this Application.
Background of Gastrointestinal (GI) Physiology and Regulation
Shown in conjunction with FIG. 1, the gastrointestinal (GI) tract is a continuous muscular digestive tube that winds through the body. The organs of the GI tract are the mouth, pharynx (not shown), esophagus 3, stomach 54, small intestine (duodenum 7, jejunum, and ileum), and large intestine (cecum, ascending colon, transverse colon, and descending colon).
The gastrointestinal (GI) tract has a nervous system all its own, which is the enteric nervous system 21. This is shown in conjunction with FIG. 2. It lies entirely in the wall of the gut, beginning in the esophagus 3 and extending all the way to the anus. The enteric nervous system has about 100 million neurons, almost exactly equal to the number in the entire spinal cord. It especially controls gastrointestinal movements and secretion. The enteric nervous system is composed mainly of the two plexuses, 1) the myenteric plexus 22, which is the outer plexus lying between the longitudinal and circular muscle layers, and 2) the submucosal plexus 23 that lies in the submucosa. The nervous connection within and between these two plexuses is depicted in FIG. 2. The myenteric plexus controls mainly the gastrointestinal movements, and the submucosal plexus controls mainly gastrointestinal secretion and local blood flow. As also depicted in FIG. 2, the sympathetic and parasympathetic fibers connect with the myenteric 22 and the submocosal 23 plexus. Although the enteric nervous system can function on its own, stimulation by the parasympathetic 25 and sympathetic 26 systems can further activate or inhibit gastrointestinal functions. The autonomic nerves influence the functions of the gastrointestinal tract by modulating the activities of neurons of the enteric nervous system 21.
Shown in conjunction with FIGS. 2 and 3, sympathetic innervation of the gastrointestinal tract is mainly via postganglionic adrenergic fibers whose cell bodies are located in pre-vertebral and parabertabral ganglia. The celiac, superior and inferior mesenteric, and hypogastric plexus provide sympathetic innervation to various segments of the GI tract. Activation of the sympathetic nerves usually inhibits the motor and secretory activities of the GI system.
Parasympathetic innervation of the GI tract down to the level of the transverse colon is provided by branches of the vagus nerves (10th cranial nerve). Excitation of parasympathetic nerves usually stimulates the motor and secretory activities of the GI tract.
The stomach 54 is richly innervated by extrinsic nerves and by the neurons of the enteric nervous system 21. Axons from the cells of the intramural plexus innervate smooth muscle and secretory cells.
The emptying of gastric contents is regulated by both neural and hormonal mechanisms. The duodenal and jejunal mucosa contain receptors that sense acidity, osmotic pressure, certain fats and fat digestion products, and peptides and amino acids This is depicted in FIG. 4. The chyme that leaves the stomach is usually hypertonic and it becomes even more hypertonic because of the action of the digestive enzymes in the duodenum. Gastric emptying is slowed by hypertonic solutions in the duodenum, by duodenal pH below 3.5, and by the presence of amino acids and peptides in the duodenum, The presence of fatty acids or monoglycerides (products of fat digestion) in the duodenum also dramatically decreases the rate of gastric emptying.
Parasympathetic innervation to the stomach is supplied by the vagus nerves, while sympathetic innervation to the stomach is provided by the celiac plexus. In general, parasympathetic nerves stimulate gastric smooth muscle motility and gastric secretions, whereas sympathetic activity inhibits these function. Numerous sensory afferent fibers leave the stomach in the vagus nerves; some of these fibers travel with sympathetic nerves. Other sensory neurons are the afferent links between sensory receptors and the intramural plexuses of the stomach. Some of these afferent fibers relay information intragastric pressure, gastric distention, intragastric pH, or pain.
Shown in conjunction with FIG. 5 is the fundus 15, the body 17, and antrum 19 of the stomach 54. After eating, when a wave of esophageal peristalsis begins, a reflex causes the LES to relax. This relaxation of the LES is followed by receptive relaxation of the fundus 15 and body 17 of the stomach. The stomach 54 will also relax if it is filled directly with gas or liquid. The nerve fibers in the vagi are a major efferent pathways for reflex relaxation of the stomach 54.
FIG. 6 depicts the three main muscle layers of the stomach 54, which are the longitudinal layer 14, the circular layer 16, and the oblique layer 18. The complex and coordinated activity of these muscle layers is responsible for the normally efficient gastric motility. Whereas, the gastric pacing disclosed here from around the antral area of the stomach 54, disrupts the normal gastric motility.
Normally, the smooth muscle of the GI tract is excited by almost continual slow, intrinsic electrical activity along the membranes of the muscle fibers. This activity has two basic types of electrical waves: 1) slow waves and 2) spikes. This is shown in conjunction with FIG. 7. Most gastrointestinal contractions occur rhythmically, and this rhythm is determined mainly by the frequency of the slow waves of the smooth muscle membrane potential. Their intensity usually varies between 5 and 15 millivolts, and their frequency ranges in different parts of the human gastrointestinal tract between 3 and 12 per minute. The rhythm of contraction of the body of the stomach is about 3 per minute (and in the duodenum is about 12 per minute).
The electrical activity of the GI tract is shown in conjunction with FIG. 7. For example, the contraction of small intestinal smooth muscle occurs when the depolarization caused by the slow wave exceeds a threshold for contraction. When depolarization of a slow wave exceeds the electrical threshold, a burst of action potentials 29 occurs. The action potentials elicit a much stronger contraction than occurs in the absence of action potentials. The contractile force increases with increasing number of action potentials.
Action potentials in gastrointestinal smooth muscle are more prolonged (10 to 20 msec) than those of skeletal muscle and have little or no overshoot. The rising phase of the action potentials is caused by ion flow through channels that conduct both Ca++ and Na+ and are relatively slow to open. Ca++ that enters the cell during the action potential helps to initiate contraction.
When the membrane potential of gastrointestinal smooth muscle reaches the electrical threshold, typically near the peak of a slow wave, a train of action potentials (1 to 10/sec) is fired. The extent of depolarization of the cells and the frequency of action potentials are enhanced by some hormones and paracrine agonists and by compounds liberated from excitatory nerve endings. Inhibitory hormones and neuroefector substances hyperpolarize the smooth muscle cells and may diminish or abolish action potential spikes.
Slow waves that are not accompanied by action potentials elicit weak contractions of the smooth muscle cells (FIG. 7). Much stronger contractions are evoked by the action potentials that are intermittently triggered near the peaks of the slow waves. The greater the frequency of action potentials that occur at the peak of a slow wave, the more intense is the contraction of the smooth muscle. Because smooth muscle cells contract rather slowly (about one tenth as fast as skeletal muscle cells), the individual contraction caused by each action potential in a train do not cause distinct twitches; rather, they sum temporally to produce a smoothly increasing level of tension (FIG. 7).
Between trains of action potentials the tension developed by gastrointestinal smooth muscle falls, but not to zero. This nonzero resting, or baseline, tension of smooth muscle is called tone. The tone of gastrointestinal smooth muscle is altered by neuroeffectors, hormones, paracrine substances, and drugs.
Control of the contractile and secretory activities of the gastrointestinal tract involves the central nervous system, the enteric nervous system, and hormones and paracrine substances. The autonomic nervous system typically only modulates the patterns of muscular and secretary activity; these activities are controlled more directly by the enteric nervous system.
In the current invention, as shown in conjunction with FIG. 8, a lead and a rechargeable implantable pulse generator is surgically implanted in the body. By stimulating the stomach wall with the system described in this disclosure, using a site and frequency which competes with the intrinsic rhythm, the normal gastric motility is interfered with, and general decrease of normal gastric motility occurs. The stomach is empties less efficiently.
Shown in conjunction with FIG. 9, with the stomach not emptying as efficiently, satiety signals which are sent to the brain (via the vagus nerves), make the patients feel less hungry. With the capacity to handle less food through the GI tract, and at the same time the patients feeling less hungry, therapy is provided for obesity and weight loss. Advantageously, in the method and system of this invention, this process is controllable and reversible utilizing an implanted lead and a programmable rechargeable implantable pulse generator.
This application is also related to co-pending applications entitled “METHOD AND SYSTEM FOR VAGAL BLOCKING WITH OR WITHOUT VAGAL STIMULATION TO PROVIDE THERAPY FOR OBESITY AND OTHER GASRTOINTESTINAL DISORDERS USING RECHARGEABLE IMPLANTED PULSE GENERATOR”, 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
Prior art is generally directed to adapting cardiac pacemaker technology to gastric pacing. But, the requirements of gastric pacing are significantly different from those of cardiac pacing.
U.S. Pat. No. 6,615,084 (Cigaina) is generally directed to a process of using electrostimulation for treating obesity. An implantable pulse generator (similar to cardiac pacemaker) appears to be used even though details are not provided for stimulation technology.
U.S. Pat. No. 5,423,872 (Cigaina) is also generally directed to a process for treating obesity and syndromes related to motor disorders of the stomach. There is no disclosure or suggestion for an inductively coupled system with an implanted stimulus-receiver and an external stimulator for supplying the electrical pulses, or for recharging an implantable system.
U.S. Pat. No. 5,690,691 (Chen et al.) is generally directed to a gastric pacemaker having phased multi-point stimulation. This disclosure is aimed primarily at having multiple electrodes throughout the gastrointestinal tract and providing phased electrical stimulation to either enhance or attenuate the peristaltic movement to treat eating disorders or diarrhea.
U.S. Pat. No. 6,321,124 B1 (Cigaina) is generally directed to the implantable lead aspect of a gastrointestinal pacing system.
U.S. Pat. No. 6,104,955 (Bourgeois) and U.S. Pat. No. 5,861,014 (Familoni) are generally directed to pulse generator systems featuring sensors for sensing gastric electrical activity, and pacing capabilities.
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 (IPG) 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. 6,611,715 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 disclosure is advantageous because it provides an ideal power source. The high output requirements of gastric pacing (which are met by high amplitude pulses and very long pulse duration (compared to cardiac pacing) are ideally met by the system and method of the current disclosure. This system is advantageous because it eliminates repeated surgeries which are required for subcutaneously implanted pulse generator changes. Additional advantage of the system and method of the current disclosure is that the external stimulator can be remotely interrogated and programmed over the internet. This eliminates the need for patient to visit physician's office or clinic every time the device needs to be programmed.
SUMMARY OF THE INVENTION
The method and system of the current invention overcomes many shortcomings of the prior art by providing a system for providing pulses to gastric wall 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, eating disorders or for inducing weight loss.
Accordingly, in one aspect of the invention, electrical pulses are provided to gastric wall utilizing a rechargeable implantable pulse generator.
In another aspect of the invention, the electrical pulses to the gastric wall are provided for at least one of obesity, inducing weight loss, eating disorders, obsessive compulsive disorders, and motility disorders.
In another aspect of the invention, the pulse amplitude delivered to sympathetic nervous system can range from 0.25 volt to 25 volts.
In another aspect of the invention, the pulse width of electrical pulses delivered can range from 5 milli-seconds to 2 seconds.
In another aspect of the invention, the frequency of electrical pulses delivered to sympathetic nervous system can range from 1 cycle/second to 100 cycles/second.
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 feedthrough 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 the stimulation and/or blocking pulses to the gastric wall of a patient.
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 one electrode(s) which is/are made of a material selected from the group consisting of platinum, platinum/iridium alloy, platinum/iridium alloy coated with titanium nitride, and carbon.
These and other objects are provided by one or more of the embodiments described below.
BRIEF DESCRIPTION OF THE DRAWINGS
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 showing general anatomy of the gastrointestinal (GI) tract.
FIG. 2 is a diagram showing control of the enteric nervous system by the autonomic nervous system (parasympathetic and sympathetic).
FIG. 3 is a simplified diagram depicting sympathetic and parasympathetic innervation of the gastrointestinal (GI) tract.
FIG. 4 is a diagram depicting control of gastric emptying by the sympathetic and parasympathetic activity.
FIG. 5 is a diagram showing general anatomy of the human stomach.
FIG. 6 is a diagram showing the longitudinal, circular, and oblique muscle layers of the stomach.
FIG. 7 is a diagram depicting the electrical activity of the GI tract.
FIG. 8 is a diagram showing the implanted components of the invention.
FIG. 9 is a schematic diagram showing the relationship of meals and satiety signals.
FIGS. 10 and 11 are diagrams showing the implanted components of the invention, which are a lead and rechargeable implanted pulse generator.
FIG. 12 is a simplified general block diagram of an implantable pulse generator.
FIG. 13A shows energy density of different types of batteries.
FIG. 13B shows discharge curves for different types of batteries.
FIG. 14 shows a block diagram of an implantable device which can be used as a stimulus-receiver or an implanted pulse generator with rechargeable battery.
FIG. 15 is a block diagram highlighting battery charging circuit of the implantable stimulator of FIG. 14.
FIG. 16 is a schematic diagram highlighting stimulus-receiver portion of implanted stimulator of one embodiment.
FIG. 17 depicts externalizing recharge and telemetry coil from the titanium case.
FIG. 18A depicts coil around the titanium case with two feedthroughs for a bipolar configuration.
FIG. 18B depicts coil around the titanium case with one feedthrough for a unipolar configuration.
FIG. 18C depicts two feedthroughs for the external coil which are common with the feedthroughs for the lead terminal.
FIG. 18D depicts one feedthrough for the external coil which is common to the feedthrough for the lead terminal.
FIGS. 19A and 19B depict recharge coil on the titanium case with a magnetic shield in-between.
FIG. 20 shows an implantable rechargable pulse generator in block diagram form.
FIG. 21 depicts in block diagram form, the implanted and external components of an implanted rechargable system.
FIG. 22 depicts the alignment function of rechargable implantable pulse generator.
FIG. 23 is a block diagram of the external recharger.
FIG. 24A is a schematic diagram of the implantable lead with two electrodes.
FIG. 2B is a schematic diagram of the implantable lead with three electrodes.
FIG. 25 is a schematic diagram depicting external stimulator and two-way communication through a server.
FIG. 26 is a diagram depicting wireless remote interrogation and programming of the external stimulator.
FIG. 27 is a schematic diagram depicting wireless protocol.
FIG. 28 is a simplified block diagram of the networking interface board.
FIGS. 29A and 29B are simplified diagrams showing communication of modified PDA/phone with an external stimulator via a cellular tower/base station.
DESCRIPTION OF THE INVENTION
In the method and system of this invention, a lead 40 comprising at least one pair of electrodes for providing gastric myo-electrical stimulation is laprscopically implanted in a patient. In one preferred procedure methodology, a patient undergoing general endotracheal anesthesia is positioned in lithotomy position. A minimum of three trocars are inserted. A midline supraumbilical port is used to introduce the optical system. Another port is used to introduce the stomach grasper. One other port (a subcostal port) is used to introduce the lead and subsequently the needle-driver. The back end of the lead is brought out through this left subcostal port at the completion of the abdominal portion of the operation.
The lead is then introduced into the abdomen, and inserted into a muscle tunnel. Using appropriate counter-traction on the stomach, both of the electrodes are ensured to be buried within the tunnel wall. After the electrodes have been inserted, a flexible fiberoptic gastroscopy is performed to ensure that inadvertent perforation of the needle into the lumen of the stomach has not occurred. Once the lead is satisfactorily implanted, it is secured in position with non-absorbable suture. A pocket is prepared on the anterior abdominal wall, and the rechargeable implantable pulse generator is implanted subutaneously. The skin is surgically closed in the usual manner. The electrical stimulation to the gastric wall can begin once the patient is completely healed from the surgery.
Shown in conjunction with FIGS. 8, 10, and 11, the pulses are typically provided via lead 40 between electrodes 61 and 62, for a bipolar configuration. A unipolar configuration can also be used where the pulse generator case is used as the ground electrode, i.e. the pulses are provided between electrode 61 and the case. The stimulation of the gastric muscle can be performed in one of two ways. One method is to activate one of several stored “pre-determined” programs. A second method is to “custom” program the electrical parameters which can be selectively programmed, for specific therapy to the individual patient. Additionally, if a stored program is used, it can be further adjusted or “fine tuned” by modifying any programmable parameter. The electrical parameters that can be individually modified or programmed, include variables such as pulse amplitude, pulse width, frequency of stimulation, stimulation on-time, and stimulation off-time. Table one below defines the approximate range of parameters;
TABLE 1
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Electrical parameter range delivered to the gastric wall
PARAMETERRANGE
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Pulse Amplitude0.5 Volt to 25 Volts
Pulse Width5 msec. to 2 secs
Frequency1 cycle/min to 100 cycles/min
On-time1 min. to 24 hours
Off-time1 min. to 24 hours
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The parameters in Table 1 are the electrical signals delivered to the gastric wall tissue via the two electrodes 61,62 (distal and proximal) in the gastric wall.
Without limitation and by way of example only, Low, Medium, and High output stimulation states stored in memory. For example;
- 1. LO Stim.
- Amplitude—2.5 Volts
- Pulse Width—200 msec
- 2. MED Stim.
- Amplitude—5 Volts
- Pulse Width—350 msec
- 3. HI Stim.
- Amplitude—7.5 Volts
- Pulse Width—500 msec
- Once a LO, MED, or HI stimulation program is activated, each individual parameter can be incremented up or down in small increments, within the range defined in Table 1. When parameter settings are found that work particularly well for the patient, they can be stored in the memory of the device. Any number of these “customized” programs can be stored in the memory of the pulse generator.
Shown in conjunction with FIG. 12, is an overall schematic of a conventional implantable pulse generator system to deliver electrical pulses for stimulating the gastric wall and providing therapy. The implantable pulse generator unit 391 NR is a microprocessor based device, where the entire circuitry is encased in a hermetically sealed titanium case. 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) is done via an external programmer 85. Once programmed via an external programmer 85, the implanted pulse generator 391 NR provides appropriate electrical stimulation pulses to the gastric wall 54 via the stimulating electrode pair 61,62. In this disclosure, the terms stomach, gastric wall, and gastric wall muscle are used interchangeably. Additional pulses may be provided for blocking, as described later.
Because of the high energy requirements for the pulses required for stimulating the gastric wall muscle 54 (unlike cardiac pacing), 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. 13A 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. 13B, 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.
In the 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, the implanted device 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 coupled with an implanted stimulus-receiver, or the power source can be from the implanted rechargeable battery. Shown in conjunction with FIG. 14 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 shown in FIG. 14, the IPG circuitry within the titanium case is used for all stimulation pulses whether the energy source is the internal 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. An external stimulator and recharger may also be combined within the same enclosure. 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 of this embodiment 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 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. 15, this embodiment of the invention is practiced with a rechargeable battery. 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. 16. 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 sets 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 FIG. 16, 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. 17, 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 48C may be externalized at the header portion 79 of the implanted device, and may be wrapped around the titanium can, as shown in FIGS. 18A and 18B. Shown in FIG. 18A is a bipolar configuration which requires two feedthroughs 76,77. Advantageously, as shown in FIG. 18B 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. 18C and 18D, 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 also be positioned on the titanium case as shown in conjunction with FIGS. 19A and 19B. FIG. 19A shows a diagram of the finished implantable stimulator 391R of one embodiment. FIG. 19B 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 the preferred embodiment of this invention, is shown in conjunction with FIG. 20. 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. Stimulation pulses are provided to the gastric muscle wall 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 rechargable 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. 21 are the recharging elements of the invention. The re-charging 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 re-charger receives energy from a battery 672 in the re-charger. 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 rechargeable 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 rechargeable 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 rechargeable 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. 21, 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. 22. 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 rechargeable 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. 23. In this disclosure, the words charger and recharger are used interchangeably. 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 re-charger is placed in a charger base station 680, the re-chargeable battery 672 of the re-charger 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 re-charger 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. 23, 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.
It will be clear to one skilled in the art, that existing systems such as disclosed in U.S. Pat. Nos. 6,615,084 and 5,423,872 both assigned to Cigaina can be adapted with technology disclosed in this patent application, and both patents are incorporated herein by reference.
Referring now to FIG. 24A, 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 shows a pair of electrodes 61,62 that are used for providing electrical pulses for stimulation. The lead terminal preferably is linear bipolar, even though it can be bifurcated, and plug(s) into the cavity of the pulse generator means. FIG. 24B shows an embodiment of a lead which is tripolar, where one electrode can be used for blocking pulses, and the other electrode pair can be used for stimulation pulses. Blocking is described more fully in a co-pending application.
The lead body 59 insulation may be constructed of medical grade silicone, silicone reinforced with polytetrafluoro-ethylene (PTFE), or polyurethane. With reference to electrode materials, the 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 two below.
TABLE 2
|
|
Lead design variables
ProximalDistal
EndEnd
Conductor
(connecting
Lead body-proximal
LeadInsulationand distalElectrode-Electrode-
TerminalMaterialsLead-Coatingends)MaterialType
|
LinearPolyurethaneAntimicrobialAlloy ofPureStandard Ball
bipolarcoatingNickel-Platinumand Ring
Cobaltelectrodes
BifurcatedSiliconeAnti-Platinum-Steroid
InflammatoryIridiumeluting
coating(Pt/Ir) Alloy
Silicone withLubriciousPt/Ir coated
Polytetrafluoro-coatingwith Titanium
ethyleneNitride
(PTFE)
Carbon
|
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
Shown in conjunction with FIG. 25, in one embodiment of the invention the external pulse generator 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. 26 is a simplified schematic showing the communication aspects between the stimulator 42 and/or programmer 85 and the remote hand-held computer. Similar methodology would apply if the telemetry module is in the programmer 85. 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 Envirnment (WAEW), 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. 27. 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. 27, includes 1) Wireless Mark-up Language (WML) 452 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/WML Script content. 4) A lightweight protocol stack 454 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 SML Script 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 (or programmer 85).
Shown in conjunction with FIG. 28, 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 FIGS. 29A and 29B 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. 65A and 65B. 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.
Patent Application
20050131487
