1. Field of the Invention
This invention relates generally to implantable medical devices, and more particularly to methods, apparatus, and systems for monitoring lead health and providing an alternative operation mode for an implantable medical device based upon an assessment of the lead health/condition.
2. Description of the Related Art
There have been many improvements over the last several decades in medical treatments for disorders of the nervous system, such as epilepsy and other motor disorders, and abnormal neural discharge disorders. One of the more recently available treatments involves the application of an electrical signal to reduce various symptoms or effects caused by such neural disorders. For example, electrical signals have been successfully applied at strategic locations in the human body to provide various benefits, including reducing occurrences of seizures and/or improving or ameliorating other conditions. A particular example of such a treatment regimen involves applying an electrical signal to the vagus nerve of the human body to reduce or eliminate epileptic seizures, as described in U.S. Pat. No. 4,702,254 to Dr. Jacob Zabara, which is hereby incorporated by reference in its entirety in this specification. Electrical stimulation of the vagus nerve may be provided by implanting an electrical device underneath the skin of a patient and performing a detection and electrical stimulation process. Alternatively, the system may operate without a detection system if the patient has been diagnosed with epilepsy, and may periodically apply a series of electrical pulses to the vagus (or other cranial) nerve intermittently throughout the day, or over another predetermined time interval.
Typically, implantable medical devices (IMDs) involving the delivery of electrical pulses to body tissues, such as pacemakers (heart tissue) and vagus nerve stimulators or spinal cord stimulators (nerve tissue), comprise a pulse generator for generating the electrical pulses and a lead assembly coupled at its proximal end to the pulse generator terminals and at its distal end to one or more electrodes in contact with the body tissue to be stimulated.
Occasionally, damage to the lead assembly can occur, which may cause various operational problems. Impedance measurements may be used to assess the integrity of the electrical leads that deliver the stimulation provided by a pulse generator. A change in the impedance across the leads that deliver the electrical pulses may be indicative of either or both of changes in a patient's body or changes in the electrical leads themselves. For example, damage in the lead, which may be induced by a break in one or more filaments in a multifilament lead wire, or changes in the body tissue where stimulation is delivered, may affect the efficacy of the stimulation therapy. Therefore, it is desirable for changes in the lead impedance, which may be indicative of various changes or malfunctions, to be accurately detected.
For instance, the integrity of the leads that deliver stimulation is of interest to insure that the proper therapy dosage is delivered to the patient. Some IMDs, most notably pacemakers, provide a voltage-controlled output that is delivered to one or more body locations (typically the heart). Other IMDs, such as a vagus nerve stimulator device developed by Cyberonics, Inc., provide a current-controlled output. Generally, however, state-of-the-art measurements of lead impedance involve an analysis of the delivery of a voltage signal from a capacitive (C) energy storage component through the resistive (R) lead impedance and an examination of the decay of that signal based upon a time-constant proportional to the product of the resistance and capacitance (RC). The total equivalent impedance present at the leads and the known energy source total equivalent capacitance cause a time-constant discharge curve. As the voltage on the capacitance is discharged through the resistance, the exponential decay of this voltage may be monitored to determine the decay time constant RC. From that time constant and an estimate of the known equivalent capacitance C, the equivalent resistance R presented by the leads may be mathematically estimated. However, this type of measurement may lead to inaccuracies for a number of reasons, including the fact that the discharging of the voltage signal may be affected by other resistances and capacitances in the system, the accuracy of the capacitor, the time, voltage, and algorithmic accuracies of the measurement system, and the like. Also, on occasions, false impedance readings that are not necessarily representative of the true condition of the leads may occur using current methodologies. These false readings may be misinterpreted and an inappropriate action may be performed by the implantable device based upon these false readings. It would be desirable to have a more efficient and accurate method, apparatus, and/or system to measure or assess the health of leads that deliver electrical stimulation or therapy.
The present invention is directed to overcoming, or at least reducing, the effects of, one or more of the problems set forth above.
In one aspect of the present invention, a method is provided for determining an adverse operational condition associated with a lead assembly in an implantable medical device used for providing a therapeutic electrical signal to a cranial nerve. A first impedance associated with the lead assembly configured to provide the therapeutic electrical signal to a cranial nerve is detected. A determination is made as to whether the first impedance is outside a first predetermined range of values. A second impedance is detected. The detection of the second impedance is performed within a predetermined period of time from the time of the detection of the first impedance. A determination is made as to whether the second impedance is outside a second predetermined range of values. A determination that a lead condition problem exists is made in response to a determination that the first is outside the first predetermined range of values and second impedance is outside the second predetermined range of values. The implantable medical device is prevented from providing the therapeutic electrical signal to the cranial nerve in response to determining that the lead condition problem exists.
In another aspect of the present invention, a method is provided for determining an adverse operational condition associated with a lead assembly in an implantable medical device used for providing a therapeutic electrical signal to a cranial nerve. A first test is performed to determine if a first indication of a lead break is present. A first remedial action is performed based upon a determination that the first indication of a lead break is present. A second test is performed to determine if a second indication of a lead break is present. The second indication of the lead break indicates a significant lead break. A second remedial action is performed based upon a determination that the second indication of a lead break is present. The second remedial action comprises preventing the implantable medical device from applying the therapeutic electrical signal to the cranial nerve.
In yet another aspect of the present invention, an implantable medical device. for determining an adverse operational condition associated with a lead assembly coupled to the implantable medical device. The implantable medical device comprises a stimulation unit to provide a therapeutic electrical signal to a cranial nerve, through a lead operatively coupled to the IMD; an impedance detection unit to provide a first impedance data and a second impedance data; and a controller operatively coupled to the stimulation unit and the impedance detection unit. The controller is adapted to determine that a significant lead condition problem is present in response to a determination that the first and second impedance data are outside a predetermined range of values. The controller is adapted to prevent the stimulation unit from providing the therapeutic electrical signal to the cranial nerve in response to the determination that the significant lead condition problem is present.
In yet another aspect of the present invention, a method is provided for determining a condition associated with a lead assembly in an implantable medical device for providing a therapeutic electrical signal to a cranial nerve. The lead condition of the lead assembly is monitored. Data relating to the lead condition is received. A lead condition analysis is performed to determine whether a lead problem is present. A determination is made as to whether the lead condition is a significant lead condition. The implantable medical device is prevented from providing the therapeutic electrical signal to the cranial nerve upon a determination that the lead condition is a significant lead condition. A secondary operation mode of the implantable medical device is implemented in response to a determination that the lead condition is not a significant lead condition.
The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which:
While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
Illustrative embodiments of the invention are described herein. In the interest of clarity, not all features of an actual implementation are described in this specification. In the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the design-specific goals, which will vary from one implementation to another. It will be appreciated that such a development effort, while possibly complex and time-consuming, would nevertheless be a routine undertaking for persons of ordinary skill in the art having the benefit of this disclosure.
Cranial nerve stimulation has been proposed to treat a number of medical conditions pertaining to or mediated by one or more structures of the nervous system of the body, including epilepsy and other movement disorders, depression, anxiety disorders, bipolar disorder, autism and other neuropsychiatric disorders, dementia, head trauma, coma, migraine headache, obesity, eating disorders, sleep disorders, cardiac disorders (such as congestive heart failure and atrial fibrillation), hypertension, endocrine disorders (such as diabetes and hypoglycemia), and pain, among others. See, e.g., U.S. Pat. Nos. 4,867,164; 5,299,569; 5,269,303; 5,571,150; 5,215,086; 5,188,104; 5,263,480; 6,587,719; 6,609,025; 5,335,657; 6,622,041; 5,916,239; 5,707,400; 5,231,988; and 5,330,515. Despite the numerous disorders for which cranial nerve stimulation has been proposed or suggested as a treatment option, the fact that detailed neural pathways for many (if not all) cranial nerves remain relatively unknown, makes predictions of efficacy for any given disorder difficult. Moreover, even if such pathways were known, the precise stimulation parameters that would modulate particular pathways relevant to a particular disorder generally cannot be predicted.
Embodiments of the present invention provide for an implantable medical device (IMD) that is capable of monitoring the general state, condition or health of leads coupled to the IMD. The IMD may experience various operational difficulties as a result of problems associated with the lead condition. The lead condition/health may include a break in the lead and/or an electrical short in a conductor coupled to the lead. Problems resulting from the lead condition(s) may include, but are not limited to, a degradation of tissue-matter proximate to the lead, corrosion of the lead, contamination of or damage to the tissue proximate to the lead, pain experienced by a patient, charge imbalance on the IMD electrodes, improper delivery of therapy, etc. Utilizing embodiments of the present invention, the general health/condition of the lead may be monitored and one or more remedial actions may be performed.
An increase or decrease in a controlled current delivered by the IMD, beyond pre-determined tolerance levels may be indicative of unusually high or unusually low lead impedances. Unusually high currents may be indicative of an electrical short associated with the lead. Unusually low currents may be indicative of a lead break. Embodiments of the present invention provide for utilizing a plurality of measurements of parameters potentially indicative of problem(s) associated with the lead, and to take at least one remedial action. For example, a plurality of lead impedance measurements may be made to determine whether the health/condition of a lead has been compromised. Acquiring a plurality of measurements upon which to assess lead condition/health reduces the possibility of a false indication of a lead condition problem. Further, multiple lead parameter measurements may shed light upon an during certain time periods or certain positions of the patient's body. For example, intermittent lead problems may occur in some cases only when the patient's body is in a particular position, such as a position of overly extended arms. If reliance on a single measurement is made, an overreaction to an intermittent lead problem may occur, or in other cases the problem may not be detected at all. The present invention provides for a reduction in this potential overreaction.
On the other hand, if a severe lead health/condition is detected, the severity of this problem may be verified by multiple measurements of parameters indicative of a lead condition problem, and any of a range of appropriate remedial actions may then be taken. Embodiments of the present invention provide for utilizing a plurality of types of measurements, such as lead impedance measurements, charge imbalance measurements, low current measurements, high current measurements, power output measurements, energy output measurements, charge delivered per pulse measurements, “make-up” voltage measurements, etc., to detect possible problems in lead health. Further, one or more of these parameters may be measured multiple times to better identify the severity and frequency of the lead condition problem. For example, lead problems may be categorized into groups, such as 1) rare intermittent problems, 2) frequent intermittent problems, 3) constant lead problems, etc., and may be identified based upon the measurements described herein. Reactions to a lead condition problem may be based upon these categorizations. Further, the measurements may be repeated at pre-determined intervals and numbers to ensure reliable and accurate assessment of the lead health. Statistical analyses may be performed based upon the frequency of lead problems, severity of the lead problems, the type of measurements indicative of lead problems, etc., which may shed light as to the actual lead condition/health.
Based upon the assessment of the lead health, various actions may be provided by embodiments of the present invention. This may include performing one or more actions selected from a range of actions, wherein the least severe action in the range may be ignoring intermittent problems, and the most severe may be a full scale shut down of operations of the IMD, which may include notifying the patient, physician, and/or manufacturer of the condition. Other steps, such as reduction in one or more electrical parameters defining the therapeutic electrical signal delivered by the IMD, may also be performed as a remedial action. Other remedial actions may include reducing the frequency of delivery of the therapeutic electrical signal, and/or performing a pre-stimulation assessment of the lead condition prior to delivery of the therapeutic electrical signal to ensure that the health of the lead is acceptable and capable of delivering the signal to the target tissue. In this manner, intermittent problems, such as lead breaks occurring when a patient is in a certain position (e.g., reclining, turning the head, raising an arm), may be bypassed by rescheduling delivery of therapy until a later pre-stimulation assessment operation ensures that the current lead health is acceptable.
Turning now to
A stimulating nerve electrode assembly 125 (
In one embodiment, the electrode assembly 125 has an open helical design, which is self-sizing and flexible to minimize mechanical trauma to the nerve and allow body fluid interchange with the nerve. The electrode assembly 125 preferably conforms to the shape of the nerve, providing a low stimulation threshold by allowing a large stimulation contact area with the nerve. Structurally, the electrode assembly 125 comprises at least one ribbon electrode, of a conductive material such as platinum, iridium, platinum-iridium alloys, or oxides of the foregoing.
In one embodiment, the IMD is used to perform active stimulation in response to an input received by the IMD from a sensor. Other embodiments of the present invention use passive stimulation to deliver a continuous, periodic, or intermittent electrical signal to the vagus nerve according to a programmed on/off duty cycle without the use of sensors to trigger therapy delivery. Both passive and active stimulation may be combined or delivered by a single IMD according to the present invention. Either or both modes may be appropriate to treat the particular disorder diagnosed in the case of a specific patient under observation.
The electrical signal generator 110 may be programmed with an external computer 150 using programming software of the type copyrighted by the assignee of the instant application with the Register of Copyrights, Library of Congress, or other suitable software based on the description herein. In one embodiment, a programming wand 155 can be used to facilitate radio frequency (RF) communication between the computer 150 (
By providing the therapeutic electrical signal, the electrical signal generator 110 may treat a disorder or a medical condition of a patient. A generally suitable form of neurostimulator for use in the method and apparatus of the present invention is disclosed, for example, in U.S. Pat. No. 5,154,172, assigned to the same assignee as the present application. A commercially available example of such a neurostimulator is available from Cyberonics, Inc., Houston, Tex., the assignee of the present application. Certain parameters defining the therapeutic electrical signal generated by the electrical signal generator 110 are programmable, such as by means of an external programmer in a manner conventional for implantable electrical medical devices.
Turning now to
Referring again to
The controller 210 may comprise various components, such as a processor 215, a memory 217, etc. The processor 215 may comprise one or more microcontrollers, microprocessors, etc., that are capable of performing various executions of software components. The memory 217 may comprise various memory portions where a number of types of data (e.g., internal data, external data instructions, software codes, status data, diagnostic data, etc.) may be stored. The memory 217 may comprise random access memory (RAM) dynamic random access memory (DRAM), electrically erasable programmable read-only memory (EEPROM), flash memory, etc.
The IMD 200 may also comprise a stimulation unit 220. The stimulation unit 220 is capable of generating and delivering stimulation signals to one or more electrodes via leads. A number of leads 122 may be coupled to the IMD 200. Therapy may be delivered to the leads 122 by the stimulation unit 220 based upon instructions from the controller 210. The stimulation unit 220 may comprise various circuitry, such as stimulation signal generators, impedance control circuitry to control the impedance “seen” by the leads, and other circuitry that receives instructions relating to the type of stimulation to be performed. The stimulation unit 220 is capable of delivering a controlled current stimulation signal to a target tissue over the leads 122 via one or more electrodes 125. A more detailed illustration of the stimulation unit 220 is provided in
The IMD 200 may also comprise a power supply 230. The power supply 230 may comprise a battery, voltage regulators, capacitors, etc., to provide power for the operation of the IMD 200, including delivering the stimulation signal. The power supply 230 comprises a power-source battery that in some embodiments may be rechargeable. In other embodiments, a non-rechargeable battery may be used. The power supply 230 provides power for the operation of the IMD 200, including electronic operations and the stimulation function. The power supply 230 may comprise a lithium/thionyl chloride cell or a lithium/carbon monofluoride cell (LiCFx). Other battery types known in the art of implantable medical devices may also be used.
The IMD 200 also comprises a communication unit 260 capable of facilitating communications between the IMD 200 and various devices. In particular, the communication unit 260 is capable of providing transmission and reception of electronic signals to and from an external unit 270. The external unit 270 may be a device that is capable of programming various modules and stimulation parameters of the IMD 200. In one embodiment, the external unit 270 is a computer system that is capable of executing a data-acquisition program. The external unit 270 may be controlled by a healthcare provider, such as a physician, at a base station, for example, in a doctor's office. The external unit 270 may be a computer, preferably a handheld computer or PDA, but may alternatively comprise any other device that is capable of electronic communications and programming, e.g., a programmable cellphone. The external unit 270 may download various parameters and program software into the IMD 200 for programming the operation of the implantable medical device. The external unit 270 may also receive and upload various status conditions and other data from the IMD 200. The communication unit 260 may be hardware, software, firmware, and/or any combination thereof. Communications between the external unit 270 and the communication unit 260 may occur via a wireless or other type of communication, illustrated generally by line 275 in
The IMD 200 may also comprise diagnostic unit 290, a therapy mode control unit 280, a lead condition detection unit 285, and an impedance detection unit 265. The diagnostic unit 290 may provide for performing various diagnostics, such as lead impedance tests, tests associated with the stimulation signals, system diagnostic tests, etc., which are described in further detail below. Upon receiving instructions from the external unit 270, the IMD 200 may perform various diagnostics tests as directed by the diagnostics unit 290 and the controller 210. In one embodiment, examples of the lead impedance test may include verifying the impedance of the lead to determine whether there is a problem in the electrical path defined by the path from the IMD 200, through the leads, through the electrodes, and onto the portion of the patient's body targeted for stimulation. Further tests performed by the diagnostic unit 290 may include verifying automatic capture of various patient data, verifying proper reception of data via sensing electrodes, verifying endogenous nerve activity (i.e., electrical activity naturally occurring in the nerve, independent of the therapeutic electrical signal), verifying the integrity and characteristics of the therapeutic electrical signal, verifying whether particular portions of a nerve (e.g., the A-fiber, the B-fibers and/or the C-fiber) are being adequately targeted. This determination may be made by examining the data detected by one or more sensors, (e.g., a sensor electrode in communication with the IMD 200).
The impedance detection unit 265 is capable of acquiring impedance data relating to leads coupled to the IMD 200. The impedance detection unit 265 is capable of performing measurements at pre-determined intervals, or upon a command from the controller 210. A more detailed illustration of the impedance detection unit 265 is provided in
The lead condition detection unit 285 is capable of assessing the health or condition of the lead(s) coupled to the IMD 200 based upon various parameters, e.g., data from the lead detection unit 265 and/or the diagnostic unit 290. Based upon the condition of the lead, a determination is made as to whether the lead problem is a constant or permanent problem, or an intermittent problem. The lead condition detection unit 285, in one embodiment, is capable of determining the severity and the type of permanent or intermittent lead problem that may be detected. Further, in one embodiment, the lead condition detection unit 285 may perform a ranking type function, ranking the degree of the severity of the lead health (e.g., ranking an error as a rare and serious intermittent error, a frequent and major intermittent error, or a constant and minor error. Further description of detecting the lead condition performed by the lead condition detection unit 285 is provided below.
Based upon the assessment performed by the lead condition detection unit 285, the therapy mode control unit 280 may control the operations performed by the stimulation unit 220. The therapy mode control unit 280 may define the stimulation pulses to be delivered to the nerve tissue according to parameters and waveforms that may be programmed into the IMD 200 using the external unit 270. The therapy mode control unit 280 controls the operation of the stimulation unit 220, which generates the stimulation pulses according to the parameters defined by the controller 230; and in one embodiment, provides these pulses to the connector 116 for delivery to the patient via lead assembly 122 and electrode assembly 125 (see
The therapy mode control unit 280 is capable of controlling the mode in which the IMD 200 operates based upon data from the lead condition detection unit 285. Based upon the type of lead health/condition detected, the therapy mode control unit 280 may cause a change in the operation mode of the IMD 200. For example, upon detection of a serious and/or constant lead health error (e.g., a constant lead short or a lead break), the therapy mode control unit 280 may simply prevent further delivery of therapeutic electrical signals until further evaluation and/or adjustments of the leads are performed.
In instances where an intermittent lead condition problem is detected, the therapy mode control unit 280 may prompt the IMD 200 to enter an alternative/secondary operation mode (as opposed to a normal operation mode when no lead condition problems are detected). The alternative/secondary operation mode of the IMD 200 may take on various forms of modified delivery of stimulation signals, such as a reduction in the energy output provided by the stimulation electrical signal. Further, other implementations of a secondary operation, such as a pre-stimulation operation check mode may be implemented. The pre-stimulation operation mode may include performing an assessment of the lead health immediately prior to delivery of a therapeutic electrical signal burst. The pre-stimulation assessment may include a pre-determined set of diagnostic-type tests that may be performed substantially immediately before the delivery of a therapeutic electrical signal. The therapy mode control unit 280 is capable of controlling the output provided by the stimulation unit 220. Other operational modifications, such as turning off a particular lead, may also be performed. In this manner, a different type of stimulation that includes a different of electrode usage for delivery of therapy may be provided. Further, other reactions, such as utilizing a uni-polar delivery of the therapeutical electrical signal, instead of a more conventional bipolar delivery, may be implemented. The uni-polar mode may include delivery of a stimulation signal via a single lead, wherein the electrical reference points (anode and cathode) are the lead tip and the case or shell 121 of the IMD 200.
Further, embodiments of the present invention provide for a notification function to be performed upon detection of adverse lead conditions. For example, notification to the patient may be performed upon detection of a lead health issue. Other notifications, such as logging the error, communicating the error to a healthcare professional (e.g., the physician), alerting the manufacturer of one or more components associated with the IMD 200, etc., may be performed. These notifications may then be utilized by the recipient to implement changes, such as surgical adjustment of the leads, adjustment of the therapeutic electrical signal delivery, modification to the IMD or related equipment, etc. The communication unit 260 is capable of performing the notification described above. The communication unit 260 may comprise a variety of types of communication interfaces that are capable of providing instant notification to the patient, the physician, the manufacturer, etc. The electronic communication means may be comprised within the communication unit 260 that provide for communication via the internet to the various targeted recipients of the notification described herein.
It will be recognized that one or more of the blocks 210-290 of
Turning now to
Embodiments of the present invention provide for utilizing the delivery of a constant current signal for delivery of a therapeutic electrical signal, and measurement of the impedance experienced by the leads 122. In a preferred embodiment, the controlled or constant current signal provided by the stimulation unit 220 is independent of the impedance experienced across the leads 122. For example, even if the impedance experienced across the leads 122 changes, the op amp 320, in conjunction with the amplifier control circuitry 310, adjusts to deliver a controlled or constant current despite the change in the impedance experienced across the leads 122.
Since a controlled, constant current is delivered despite variations in the impedance across the leads 122, the voltage across the lead terminals can be used to provide an indication of the lead impedance. For example, if the nerve tissue to which the leads 122 are connected has an impedance of 1000 ohms, a particular stimulation may call for a one milliamp constant current signal. In this case, even if a 5000 ohms impedance is experienced across the leads 122, the stimulation unit 220 will still provide a one milliamp current. Hence, the power may vary but the current remains constant. In other words, the op amp 320 will stabilize itself utilizing various circuitry, including the amplifier control circuitry 310, to provide a constant current signal even if the impedance experienced by the leads 122 varies during the period the signal is provided. Therefore, using Ohm's Law, V=IR, a measurement of the voltage across the leads 122 will provide an indication of the actual impedance experienced by the leads 122.
Turning now to
Although certain embodiments may be implemented without it, the A/D converter 420 may be beneficial for enhancing the resolution of the voltage signal, thereby providing for enhanced analysis of the voltage across the leads 122. Based upon the voltage across the leads 122, and the constant current signal provided by the stimulation unit 220, the impedance calculation unit 430 calculates the impedance by dividing the voltage across the lead terminals 122 by the current delivered by the stimulation unit 220. The impedance calculation unit 430 may be a hardware unit, a software unit, a firmware unit, or any combination thereof, which may be located in various portions of the IMD 200, including in the impedance detection unit 265, in the stimulation controller 230, in the power source controller 220, or in any other portion of the IMD 200.
In an alternative embodiment, the calculation described as being performed by the impedance calculation unit 430 may alternatively be performed by the external unit 270, which may receive the signal relating to the constant current stimulation signal and the measured voltage signal. One of the advantages of utilizing the embodiments provided by the present invention is that substantially any size of a constant or controlled current stimulus signal may be used to perform the impedance measurement, thereby conserving battery power of the implantable medical device 200. Accordingly, the smallest stimulation signal that may reliably be provided by the stimulation unit 220 may be used to perform the impedance measurement. Thus, the impedance measurement may be made without imposing a significant charge depletion burden on the battery. Additionally, the impedance of the leads 122 themselves is also accounted for when analyzing the impedance. Furthermore, the A/D converter 420 may be calibrated prior to the operation of the implantable medical device 200, for example, during the manufacturing process.
Turning again to
The system illustrated in
Turning now to
Upon implementing the step of monitoring of the lead condition, the IMD 200 may receive data relating to the lead condition (block 520). This data may include various parameters that may be associated with the condition of the lead. These parameters, for example, may include data relating to low current, high current, lead impedance, power output, energy output, charge delivered per pulse, charge imbalance, “make-up” voltage, experienced by the IMD 200. The “make-up” voltage refers to the boost in voltage or current provided by the IMD 200 in response to detecting a reduction of voltage across the electrodes associated with the leads. For example, if a lead break is present, the IMD 200 may attempt to provide a boost in the voltage and/or current to compensate for any potential loss of energy in order to provide predetermined therapeutic signals. Embodiments of the present invention may also be implemented by examining other parameters that may be assessed by those skilled in the art having benefit of the present invention. Upon receiving the data relating to the lead condition or health, the IMD 200 may begin a lead condition evaluation process (block 530). The lead condition/health evaluation process may include various steps to determine whether a lead health problem indeed exists. Further details relating to the lead health evaluation process of
After performing the lead condition evaluation process 530, the IMD 200 may next determine whether a lead health problem is detected (block 540). If the IMD 200 determines that a lead condition/health problem is not detected, the IMD 200 may choose to continue monitoring the lead condition based upon pre-determined programming. On the other hand, if a lead condition problem is detected, the IMD 200 may perform a notification function (block 570). Various entities, such as the patient, a healthcare professional, a manufacturer of one or more components of the IMD system, etc., may be notified. This notification may also include storing of markers or “flags” that may be detected at a later time or in real time. Further, other notifications, such as an email, electronics communications, alarms, etc., may be performed.
Additionally, upon detecting a lead health problem, the IMD 200 may enter an alternative/secondary operation mode (block 560). The alternative/secondary operation mode may allow the IMD to continue to provide continuous therapeutic operation, but in a different mode as to reduce the possibility of damage caused by any particular lead problem. Further, avoiding delivery of therapy during problematic periods where intermittent problems may be detected is also made possible by the alternative/secondary operation mode. Upon entering such a alternative/secondary operation mode, the IMD 200 may perform a diagnostic process (block 580) to determine if there are any further problems associated with the lead health (block 590), or with other aspects of the IMD such as the battery. A more detailed description of entering the alternative/secondary operation mode is provided in
Turning now to
Stimulation is delivered by the IMD 200 to the tissue of the patient by any one of a number of available stimulation delivery modes, such as a constant current signal pulse. To conserve battery power, impedance may be determined using a small magnitude and/or short duration test pulse. The resultant voltage induced across the leads 122 is measured upon delivery of the test pulse. Voltage measurement may be performed by the voltage measurement unit 410 (
An analog-to-digital (A/D) conversion is preferably performed on the voltage signal measured during the test pulse. Although embodiments of the present invention may be performed without utilizing an A/D converter 420, in one embodiment, an A/D converter 420 (
Once the lead impedance is determined (block 610), the IMD 200 may determine whether the impedance is outside an acceptable, predetermined threshold or level of tolerance (block 620). Upon a determination that the impedance is not outside a threshold level, or is within an acceptable range of tolerance, the IMD 200 may continue normal operation and/or report that no lead condition problems have been detected (block 630). If the IMD 200 determines that the lead impedance is outside the threshold value, then various steps illustrated in
Upon a determination that the impedance is outside the acceptable threshold, the IMD 200 may determine one or more parameters such as battery consumption or remaining battery life (block 632), voltage on the electrode (block 634), charge imbalance (block 636), make-up or compensation voltage (block 638), and/or perform various diagnostics tests (block 640). In other words, the detection of an unacceptable impedance may be combined with one or more other parameters associated with the operation of the IMD 200 to determine whether a lead health problem indeed exists. For example, a charge imbalance, in combination with the existence of a lead impedance problem, may be indicative that a lead condition problem indeed exists.
One embodiment of performing the charge imbalance detection step may include detecting voltages on electrodes during “off time,” when no signal is being applied to the target tissue. The voltages may be examined in a differential fashion, wherein, if different voltages on each electrode exist, this may be indicative of a charge imbalance. The make-up or compensation voltage of block 638 may refer to a boost in the voltage provided by the IMD 200 to compensate for any loss of energy. A voltage boost signal (“Vboost”) may be provided by the IMD 200 to increase the amount of energy to ensure that predetermined levels of energy in the therapeutic electrical signal (or the test pulse) is delivered. However, in situations such as a lead break, the attempt to compensate by increasing the Vboost signal may not suffice and desired levels of energy delivery may not take place at all.
Based upon the detection of various parameters described above, as well as the lead impedance, the IMD 200 may perform a statistical analysis of the resultant data (block 650). This analysis may include analyzing one or more of the parameters described above (e.g., battery consumption/life, electrode voltage, charge imbalance, makeup voltage, etc.) to determine if one or more parameters enter an unacceptable range of values within predetermined time periods and/or predetermined frequency. For example, a determination is made whether a combination of one or more parameters described above enters an unacceptable range of values three times during a predetermined time frame. Other statistical analysis techniques may be used to determine whether a significant lead health issue exists. Upon performing the statistical analysis, the IMD 200 may determine if a lead problem has indeed occurred based upon the statistical analysis (block 660).
Turning now to
Based upon a detection that an operational parameter is out of tolerance, the IMD 200 may be prompted to perform a lead impedance detection as a result (block 730). The lead impedance may be measured in various manners, such as the process described above. Once the lead impedances are determined, a determination is made whether the lead impedance is out of tolerance or not within acceptable range of values (block 740). Upon a determination that the lead impedance is not out of tolerance, the IMD 200 may report that no lead problem has been detected (block 760). Upon a detection that the lead impedance is, indeed, out of tolerance, a report may be provided by the IMD 200 that there is, indeed, a possible lead condition problem (block 750). The IMD 200 may then utilize the results of description provided in
Those skilled in the art would appreciate that methods illustrated in
Turning now to
Upon a determination that a lead problem is, indeed, an intermittent problem, a pre-stimulation check may be performed by the IMD 200 (block 830). The pre-stimulation check may include a variety of types of diagnostics that may be performed prior (e.g., substantially immediately prior) to delivery of a therapeutic electrical signal burst (i.e., a serious of pulses comprising a therapeutic signal event). At a predetermined moment before a stimulation signal is delivered by the IMD, a pre-stimulation check may determine whether an immediate lead health issue exists or not. In some cases, the lead problem may only exist when the patient's body is in a certain position, therefore, a quick diagnostic check of the lead condition may be performed before the delivery of a therapeutic electrical signal burst. Upon an indication that the pre-stimulation check results in a determination that there is no lead problem, a burst of the therapeutic electrical signal may actually be delivered to the target tissue. If the pre-stimulation check indicates that there is a lead problem, the delivery of the stimulation signal may be delayed until a subsequent pre-stimulation check is performed and indicates the absence of a lead problem.
Upon a determination that the lead health problem is not an intermittent or occurrence, various actions may be performed, as exemplified in
Referring again to
Alternatively, the IMD 200 may simply disable an electrode associated with a faulty lead and enter an “alternative electrode combination mode” (block 870). The alternative electrode combination mode may include changing the usage of electrode combination to avoid the electrode associated with the problematic lead. For example, a unipolar delivery of stimulation may be performed wherein the anode and cathode associated with the delivery of the stimulation signal may be defined by one electrode and the case or shell 121 associated with the IMD 200. Alternatively, other combination of electrodes may be used when avoiding a particular electrode associated with a faulty lead. In this manner, various other alternative therapeutical processes may be implemented by those skilled in the art having benefit of the present disclosure and remain within the spirit and scope of the present invention.
Turning now to
Other notifications, such as notifying a health care professional, may also be performed (block 940). Electronic communications to a database associated with a doctor's office, for example, may be performed by the IMD 200. Other indications may include prompting the patient to notify the doctor. Further, the IMD 200 may notify manufacturers associated with one or more components of the IMD system described herein (block 950). For example, the recipients may include the manufacturer of the IMD 200, the manufacturer of the leads, the manufacturer of the electrodes, etc., and may be notified automatically upon detection of the lead problem.
In this manner, automated response to the detection of lead health problems may be performed and notifications may be stored and sent. This provides for more efficient analysis and reaction to detected problems, while maintaining as much therapeutic stimulation capability as possible.
The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. The particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below.
Number | Name | Date | Kind |
---|---|---|---|
3421511 | Schwartz et al. | Jan 1969 | A |
3760812 | Timm et al. | Sep 1973 | A |
3796221 | Hagfors | Mar 1974 | A |
4291699 | Geddes et al. | Sep 1981 | A |
4305402 | Katims | Dec 1981 | A |
4384926 | Wagner | May 1983 | A |
4407303 | Akerstrom | Oct 1983 | A |
4458696 | Larimore | Jul 1984 | A |
4459989 | Borkan | Jul 1984 | A |
4573481 | Bullara | Mar 1986 | A |
4590946 | Loeb | May 1986 | A |
4592359 | Galbraith | Jun 1986 | A |
4606349 | Livingston et al. | Aug 1986 | A |
4608985 | Crish et al. | Sep 1986 | A |
4612934 | Borkan | Sep 1986 | A |
4628942 | Sweeney et al. | Dec 1986 | A |
4630615 | Yomtov | Dec 1986 | A |
4649936 | Ungar et al. | Mar 1987 | A |
4702254 | Zabara | Oct 1987 | A |
4793353 | Borkan | Dec 1988 | A |
4821724 | Whigham et al. | Apr 1989 | A |
4827932 | Ideker et al. | May 1989 | A |
4850356 | Heath | Jul 1989 | A |
4860616 | Smith | Aug 1989 | A |
4867164 | Zabara | Sep 1989 | A |
4870341 | Pihl et al. | Sep 1989 | A |
4899750 | Ekwall | Feb 1990 | A |
4903700 | Whigham et al. | Feb 1990 | A |
4920979 | Bullara | May 1990 | A |
4964407 | Baker, Jr. et al. | Oct 1990 | A |
4969468 | Byers et al. | Nov 1990 | A |
4979511 | Terry, Jr. | Dec 1990 | A |
5003975 | Hafelfinger et al. | Apr 1991 | A |
5025807 | Zabara | Jun 1991 | A |
5095905 | Klepinski | Mar 1992 | A |
5111815 | Mower | May 1992 | A |
5137020 | Wayne et al. | Aug 1992 | A |
5137021 | Wayne et al. | Aug 1992 | A |
5139028 | Steinhaus et al. | Aug 1992 | A |
5146920 | Yuuchi et al. | Sep 1992 | A |
5154172 | Terry, Jr. et al. | Oct 1992 | A |
5179950 | Stanislaw | Jan 1993 | A |
5186170 | Varrichio et al. | Feb 1993 | A |
5188104 | Wernicke et al. | Feb 1993 | A |
5201808 | Steinhaus et al. | Apr 1993 | A |
5201865 | Kuehn | Apr 1993 | A |
5205285 | Baker, Jr. | Apr 1993 | A |
5215086 | Terry, Jr. et al. | Jun 1993 | A |
5215089 | Baker, Jr. | Jun 1993 | A |
5222494 | Baker, Jr. | Jun 1993 | A |
5231988 | Wernicke et al. | Aug 1993 | A |
5237991 | Baker, Jr. et al. | Aug 1993 | A |
5251634 | Weinberg | Oct 1993 | A |
5263480 | Wernicke et al. | Nov 1993 | A |
5269303 | Wernicke et al. | Dec 1993 | A |
5299569 | Wernicke et al. | Apr 1994 | A |
5304206 | Baker, Jr. et al. | Apr 1994 | A |
5330515 | Rutecki et al. | Jul 1994 | A |
5335657 | Terry, Jr. et al. | Aug 1994 | A |
5351394 | Weinberg | Oct 1994 | A |
5411528 | Miller et al. | May 1995 | A |
5431692 | Hansen et al. | Jul 1995 | A |
5466255 | Franchi | Nov 1995 | A |
5501702 | Plicchi et al. | Mar 1996 | A |
5507786 | Morgan et al. | Apr 1996 | A |
5522865 | Schulman et al. | Jun 1996 | A |
5531778 | Maschino et al. | Jul 1996 | A |
5534018 | Wahlstrand et al. | Jul 1996 | A |
5540730 | Terry, Jr. et al. | Jul 1996 | A |
5540734 | Zabara | Jul 1996 | A |
5549646 | Katz et al. | Aug 1996 | A |
5571150 | Wernicke et al. | Nov 1996 | A |
5575813 | Edell et al. | Nov 1996 | A |
5620474 | Koopman | Apr 1997 | A |
5658318 | Stroetmann et al. | Aug 1997 | A |
5690681 | Geddes et al. | Nov 1997 | A |
5700282 | Zabara | Dec 1997 | A |
5707400 | Terry, Jr. et al. | Jan 1998 | A |
5713936 | Staub et al. | Feb 1998 | A |
5741311 | Mc Venes et al. | Apr 1998 | A |
5743860 | Hively et al. | Apr 1998 | A |
5755742 | Schuelke et al. | May 1998 | A |
5755747 | Daly et al. | May 1998 | A |
5759199 | Snell et al. | Jun 1998 | A |
5769873 | Zadeh | Jun 1998 | A |
5796044 | Cobian et al. | Aug 1998 | A |
5814088 | Paul et al. | Sep 1998 | A |
5876425 | Gord et al. | Mar 1999 | A |
5891179 | Er et al. | Apr 1999 | A |
5897577 | Cinbis et al. | Apr 1999 | A |
5916239 | Geddes et al. | Jun 1999 | A |
5919220 | Stieglitz et al. | Jul 1999 | A |
5928272 | Adkins et al. | Jul 1999 | A |
5995868 | Osorio et al. | Nov 1999 | A |
6035237 | Schulman et al. | Mar 2000 | A |
6052624 | Mann | Apr 2000 | A |
6073050 | Griffith | Jun 2000 | A |
6104956 | Naritoku et al. | Aug 2000 | A |
6154678 | Lauro | Nov 2000 | A |
6171239 | Humphrey | Jan 2001 | B1 |
6181969 | Gord | Jan 2001 | B1 |
6208902 | Boveja | Mar 2001 | B1 |
6212431 | Hahn et al. | Apr 2001 | B1 |
6216045 | Black et al. | Apr 2001 | B1 |
6259951 | Kuzma et al. | Jul 2001 | B1 |
6269270 | Boveja | Jul 2001 | B1 |
6304787 | Kuzma et al. | Oct 2001 | B1 |
6317633 | Jorgenson et al. | Nov 2001 | B1 |
6339725 | Naritoku et al. | Jan 2002 | B1 |
6341236 | Osorio et al. | Jan 2002 | B1 |
6393325 | Mann et al. | May 2002 | B1 |
6400988 | Gurewitsch | Jun 2002 | B1 |
6418348 | Witte | Jul 2002 | B1 |
6445951 | Mouchawar | Sep 2002 | B1 |
6453198 | Torgerson et al. | Sep 2002 | B1 |
6456481 | Stevenson | Sep 2002 | B1 |
6473653 | Schallhorn et al. | Oct 2002 | B1 |
6477417 | Levine | Nov 2002 | B1 |
6490486 | Bradley | Dec 2002 | B1 |
6505074 | Boveja et al. | Jan 2003 | B2 |
6510332 | Greenstein | Jan 2003 | B1 |
6529774 | Greene | Mar 2003 | B1 |
6553263 | Meadows et al. | Apr 2003 | B1 |
6556868 | Naritoku et al. | Apr 2003 | B2 |
6587719 | Barrett et al. | Jul 2003 | B1 |
6587727 | Osorio et al. | Jul 2003 | B2 |
6600956 | Maschino et al. | Jul 2003 | B2 |
6600957 | Gadsby | Jul 2003 | B2 |
6606523 | Jenkins | Aug 2003 | B1 |
6609025 | Barrett et al. | Aug 2003 | B2 |
6620186 | Saphon et al. | Sep 2003 | B2 |
6622038 | Barrett et al. | Sep 2003 | B2 |
6622041 | Terry, Jr. et al. | Sep 2003 | B2 |
6622047 | Barrett et al. | Sep 2003 | B2 |
6648823 | Thompson | Nov 2003 | B2 |
6658294 | Zadeh et al. | Dec 2003 | B1 |
6662053 | Borkan | Dec 2003 | B2 |
6671556 | Osorio et al. | Dec 2003 | B2 |
6684105 | Cohen et al. | Jan 2004 | B2 |
6687538 | Hrdlicka et al. | Feb 2004 | B1 |
6690974 | Archer et al. | Feb 2004 | B2 |
6711440 | Deal et al. | Mar 2004 | B2 |
6718203 | Weiner et al. | Apr 2004 | B2 |
6718207 | Connelly | Apr 2004 | B2 |
6721600 | Jorgenson et al. | Apr 2004 | B2 |
6721603 | Zabara et al. | Apr 2004 | B2 |
6725092 | MacDonald et al. | Apr 2004 | B2 |
6731979 | MacDonald | May 2004 | B2 |
6745077 | Griffith et al. | Jun 2004 | B1 |
6754539 | Erickson et al. | Jun 2004 | B1 |
6757566 | Weiner et al. | Jun 2004 | B2 |
6760624 | Anderson et al. | Jul 2004 | B2 |
6760625 | Kroll | Jul 2004 | B1 |
6760628 | Weiner et al. | Jul 2004 | B2 |
6763268 | MacDonald et al. | Jul 2004 | B2 |
6778856 | Connelly et al. | Aug 2004 | B2 |
6792316 | Sass | Sep 2004 | B2 |
6795730 | Connelly et al. | Sep 2004 | B2 |
6795736 | Connelly et al. | Sep 2004 | B2 |
6799069 | Weiner et al. | Sep 2004 | B2 |
6804557 | Kroll | Oct 2004 | B1 |
6819954 | Connelly | Nov 2004 | B2 |
6819958 | Weiner et al. | Nov 2004 | B2 |
6829509 | MacDonald et al. | Dec 2004 | B1 |
6843870 | Bluger | Jan 2005 | B1 |
6845266 | Weiner et al. | Jan 2005 | B2 |
6850805 | Connelly et al. | Feb 2005 | B2 |
6875180 | Weiner et al. | Apr 2005 | B2 |
6901290 | Foster et al. | May 2005 | B2 |
6906256 | Wang | Jun 2005 | B1 |
6907295 | Gross et al. | Jun 2005 | B2 |
6920357 | Osorio et al. | Jul 2005 | B2 |
6925328 | Foster et al. | Aug 2005 | B2 |
6944489 | Zeijlemaker et al. | Sep 2005 | B2 |
6949929 | Gray et al. | Sep 2005 | B2 |
6954674 | Connelly | Oct 2005 | B2 |
6961618 | Osorio et al. | Nov 2005 | B2 |
6985775 | Reinke et al. | Jan 2006 | B2 |
6993387 | Connelly et al. | Jan 2006 | B2 |
7006859 | Osorio et al. | Feb 2006 | B1 |
7010357 | Helfer et al. | Mar 2006 | B2 |
7013174 | Connelly et al. | Mar 2006 | B2 |
7015393 | Weiner et al. | Mar 2006 | B2 |
7047074 | Connelly et al. | May 2006 | B2 |
7050851 | Plombon et al. | May 2006 | B2 |
7054686 | MacDonald | May 2006 | B2 |
7107097 | Stern et al. | Sep 2006 | B2 |
7123013 | Gray | Oct 2006 | B2 |
7171166 | Ng et al. | Jan 2007 | B2 |
7174219 | Wahlstrand et al. | Feb 2007 | B2 |
7212869 | Wahlstrom | May 2007 | B2 |
7221981 | Gliner | May 2007 | B2 |
7239924 | Kolberg | Jul 2007 | B2 |
7289856 | Karicherla | Oct 2007 | B1 |
7584004 | Caparso et al. | Sep 2009 | B2 |
20020072782 | Osorio et al. | Jun 2002 | A1 |
20020120307 | Jorgenson et al. | Aug 2002 | A1 |
20030083726 | Zeijlemaker et al. | May 2003 | A1 |
20030195601 | Hung et al. | Oct 2003 | A1 |
20040015205 | Whitehurst et al. | Jan 2004 | A1 |
20040064161 | Gunderson et al. | Apr 2004 | A1 |
20040147992 | Bluger et al. | Jul 2004 | A1 |
20040167583 | Knudson et al. | Aug 2004 | A1 |
20040172088 | Knudson et al. | Sep 2004 | A1 |
20040210291 | Erickson | Oct 2004 | A1 |
20050015128 | Rezai et al. | Jan 2005 | A1 |
20050016657 | Bluger | Jan 2005 | A1 |
20050096719 | Hammill et al. | May 2005 | A1 |
20050107858 | Bluger | May 2005 | A1 |
20050137636 | Gunderson et al. | Jun 2005 | A1 |
20050154426 | Boveja et al. | Jul 2005 | A1 |
20050154435 | Stern et al. | Jul 2005 | A1 |
20050222642 | Przybyszewski et al. | Oct 2005 | A1 |
20050272280 | Osypka | Dec 2005 | A1 |
20060025828 | Armstrong et al. | Feb 2006 | A1 |
20060058597 | Machado et al. | Mar 2006 | A1 |
20060106430 | Fowler et al. | May 2006 | A1 |
20060116733 | Gunderson | Jun 2006 | A1 |
20060167497 | Armstrong et al. | Jul 2006 | A1 |
20060173493 | Armstrong et al. | Aug 2006 | A1 |
20060184211 | Gaunt et al. | Aug 2006 | A1 |
20060224199 | Zeijlemaker et al. | Oct 2006 | A1 |
20060247706 | Germanson et al. | Nov 2006 | A1 |
20060253164 | Zhang et al. | Nov 2006 | A1 |
20060259078 | Libbus | Nov 2006 | A1 |
20060265025 | Goetz et al. | Nov 2006 | A1 |
20070027497 | Parnis et al. | Feb 2007 | A1 |
20070027498 | Maschino et al. | Feb 2007 | A1 |
20070027500 | Maschino et al. | Feb 2007 | A1 |
20070032834 | Gliner et al. | Feb 2007 | A1 |
20070060991 | North et al. | Mar 2007 | A1 |
20070073150 | Gopalsami et al. | Mar 2007 | A1 |
20070100392 | Maschino et al. | May 2007 | A1 |
20070142889 | Whitehurst et al. | Jun 2007 | A1 |
20070173902 | Maschino et al. | Jul 2007 | A1 |
20070179557 | Maschino et al. | Aug 2007 | A1 |
20070179579 | Feler et al. | Aug 2007 | A1 |
20070179584 | Gliner | Aug 2007 | A1 |
20080033503 | Fowler et al. | Feb 2008 | A1 |
20080046035 | Fowler et al. | Feb 2008 | A1 |
20080071323 | Lowry et al. | Mar 2008 | A1 |
20080200925 | Johnson et al. | Aug 2008 | A1 |
20080215110 | Gunderson et al. | Sep 2008 | A1 |
20080255582 | Harris | Oct 2008 | A1 |
20090076567 | Fowler et al. | Mar 2009 | A1 |
Number | Date | Country |
---|---|---|
2004069330 | Aug 2004 | WO |
Entry |
---|
J. Walter Woodbury and Dixon M. Woodbury, Vagal Stimulation Reduces the Severity of Maximal Electroshock Seizures in Intact Rates: Use of a Cuff Electrode for Stimulating and Recording, Department of Physiology, School of Medicine, University of Utah, Jan. 1991, pp. 94-107, vol. 14, Salt Lake City, Utah. |
Mesut Sahn, Improved Nerve Cuff Electrode Recordings with Subthreshold Anodic Currents, IEEE Transactions on Biomedical Engineering, Aug. 1998, pp. 1044-1050, vol. 45, No. 8. |
Peter J. Basser and Bradley J. Roth, New Currents in Electrical Stimulation of Excitable Tissues, Annu. Rev. Biomed. Eng. 2000, vol. 2, pp. 377-397. |
Number | Date | Country | |
---|---|---|---|
20090125079 A1 | May 2009 | US |