Abstract: An apparatus and method for the control of both central and obstructive sleep apnea using electrical stimulation on a demand basis. Implantable sensors monitor the respiration cycle and determine the occurrence of apnea events. Central apnea is sensed by the passage of an escape interval of time without the sensing of an inspiratory event and a concurrent decrease in blood oxygen saturation. Obstructive sleep apnea is sensed as an abnormal pressure differential across the airway. The diaphragm is electrically stimulated upon sensing of central apnea. The musculature of the upper airway is electrically stimulated upon sensing of an occurrence of obstructive sleep apnea. Stimulation of the upper airway is provided whenever central apnea is sensed.

Abstract: An implantable electrode system for establishing electrical contact with nerve tissue. The outer substrate of the electrode is a semi-rigid, body compatible, insulating material such as a chronically implantable polymer. The outer substrate is molded as a single structure having a central spine along the longitudinal axis of the electrode. A plurality of fingers extend orthogonally from the central spine, and are bent circularly about a radius of curvature approximating that of the nerve to be contacted. The fingers of the electrode are spread by the retractable channel of the insertion tool during the implant procedure. The retractable channel is placed over the selected nerve and a retraction knob on the handle of the insertion tool is moved in a proximal direction causing the electrode to be ejected on to the nerve. The handle of the insertion tool is curved to require a minimum of exposure of the nerve tissue.

Abstract: An apparatus for and method of measuring the current which flows through a cardiac pacing lead to artificially stimulate contractions of the myocardium. This current measurement is useful for estimating battery life and monitoring proper operation of the pacing lead and the implantable pulse generator.The measurement is accomplished by carefully controlling the gain of the output amplifier and timing the rate of charge and discharge of the output capacitor. The average pacing current can be determined from the relative charge and discharge times given that the other circuit component values are known and controlled.

Abstract: A battery impedance measurement apparatus for battery powered implantable medical apparatus in which current source means and reference impedance means are selectively connected across the battery after it has been isolated from the medical apparatus, and the resulting currents of interest are digitized to provide a factor directly related to the value of the internal impedance of the battery. The digitized value may be telemetered out of the implanted medical apparatus to enable critical decisions to be made based on the remaining life of the implanted battery. The same measurement apparatus can be used to form an accurate end-of-life signal.

Abstract: An apparatus for and method of improving muscle tone of a patient using chronic sub-tetanic electrical stimulation. For patients suffering from obstructive sleep apnea, for example, the muscles of the upper airway are provided the chronic stimulation to mitigate or prevent the adverse medical condition caused in part by excessively flaccid muscle tissue around and in the airway.A stimulation generator supplies pulses to the muscle to be treated through insulated leads which are coupled to electrodes directly in contact with the appropriate neuro-muscular tissue. The output of the stimulation generator is adjusted to a frequency of sufficiently low level as to prevent fused tetanic contraction of the stimulated muscle. The adjustment may be made manually by attending medical personnel or may be done automatically using electrodes to sense the tension of the stimulated muscle. In the automatic mode, the sensing system insures the stimulation frequency level is decreased below the threshold of muscle tetanus.

Abstract: This invention relates to steerable catheters. More particularly, this invention relates to steerable catheters comprising a flexible catheter comprising a spring coil body defining a lumen, the spring coil body having a flexible covering thereon; a deflection wire, the distal end of the deflection wire being attached to the distal end of the spring coil body; and control means attached to the proximal end of the catheter, the proximal end of the deflection wire extending through the control means and the control means having a torque means which fixedly engages said deflection wire.

Abstract: A system for the treatment of obstructive sleep apnea packaged in a collar which can be worn by a patient without any special preparation. The collar is adjustable using a fastener such as hook and latch, to accommodate variations in neck size. The collar is properly oriented using variations in physical shape and/or color. An optional feedback system permits the patient to readily verify proper orientation.The collar contains at least one sensor to monitor functioning of the respiratory system of the patient.The output of the sensor(s) is processed by battery powered electronics located within or in proximity to the collar. When an apnea episode is detected, the electronics module generates bursts of pulsatile current which are conducted to electrodes located on and positioned by the collar or in proximity to the collar.

Abstract: An insulated electrical lead for coupling the output of a neurological stimulator with the tissue to be stimulated. In most situations, the neurological stimulator is an implantable pulse generator and the tissue to be stimulated is the spinal cord, although other configurations are contemplated. The insulated electrical lead has a sealable connector at the proximal end which couples to the implantable pulse generator. The distal end contains a number of electrodes placed in close proximity to the tissue to be stimulated. A different conductor couples each of the electrodes to the proximal connector. The distal portion of the insulated lead has a deformable sigmoidal shape. The electrodes are spaced along the length of the deformable sigmoidal shape. This causes the electrodes to be displaced laterally so that specific neural tracts in the spinal cord are preferentially stimulated by various combinations of electrode polarity.

Abstract: A technique for improving the radio frequency coupling between an external programming device and a medical device implanted within a patient. The radio frequency coupling is typically used to non-invasively change the operating parameters of the implanted device, such as a cardiac pacer. A common frequency for transmission is 175 khz. At this frequency, in view of the low power and the short distances involved, positioning of the external antenna with respect to the implanted antenna becomes critical. This criticality is heightened because of the great change in transmitter antenna loading and tuning with small changes in relative position.To assist the attending medical personnel, the transmitter antenna is ordinarily mounted within a paddle-like structure. A feedback coil is placed within the same physical package. The signal induced within the feedback coil is amplified, filtered, and integrated to produce a signal which controls the output amplifier of the transmitter.

Abstract: This invention relates to steerable catheters. More particularly, this invention relates to a steerable catheter comprising a flexible catheter member having distal and proximal ends and one or more lumens, the single lumen or one of the lumens being closed at its distal end, the one or more other lumens being open, for introduction of a central guide wire or other desired object; a deflection wire having distal and proximal ends and axially extending the length of the catheter member through the lumen having the closed end, the distal end of the deflection wire being embedded in the closed end; and control means attached to the proximal end of the catheter member, the proximal end of the deflection wire extending to the control means and the control means having an engaging means which fixedly engages the deflection wire.

Abstract: A technique for monitoring the performance of a skeletal muscle used in a cardiac assist sytem. The skeletal muscle is surgically wrapped about the heart, the descending aorta, or a chamber connected in series with or parallel to the descending aorta to provide direct assistance when electrically stimulated to correspond with naturally or artifically paced heart contractions. An alternate system provides indirect assistance by improving coronary perfusion when the skeletal muscle is electrically stimulated to contract about an artificial chamber during relaxation of the myocardium. In either type or cardiac assist system, the skeletal muscle must be conditioned to perform constant contraction/relaxation within the range of normal heart rates. This conditioning occurs over a length of time which is too long to be directly managed by medical personnel in a sterile environment except experimentally. The present invention provides apparatus and techniques for managing the conditioning process automatically.

Abstract: An electrode for establishing electrical contact with nerve tissue. The electrode is chronically implantable. The outer substrate of the electrode is a semi-rigid, body compatible, insulating material such as a chronically implatable polymer. The outer substrate is molded as a single structure having a central spine along the longitudinal axis of the electrode. A plurality of fingers extend orthogonally from the central spine, and are bent circularly about a radius of curvature approximating that of the nerve to be contacted. Each of the plurality of fingers is of sufficient length to extend approximately one-half of the distance around the outer circumference of the nerve tissue. The plurality of fingers extend from the central spine in one of two opposite directions causing the electrode structure to encompass a hollow cylinder having an inside diameter the same as the nerve.

Abstract: An improved electrode for establishing electrical contact with a nerve of a patient. This electrical contact may be used to sense neural activity on the nerve or to artificially stimulate it to perform various medical treatments. The electrode has an outer cuff of an insulating material which is sutured around the nerve to be contacted. A drug impregnated layer of material is positioned inside of the outer cuff. This material is a polymeric matrix which permits the drug to leach out at a predetermined rate. The drug is a steroid such as dexamethasone sodium phosphate. The actual electrical contact is produced by metallic foil which is positioned on the surface of the drug impregnated layer of material which is located inside of the cuff. An insulated lead electrically couples the metallic foil to an electronic circuit located remote from the nerve. The leaching out of the drug serves to control irritation, swelling, and impedance of the nerve/electrode interface.

Abstract: Apparatus and method for monitoring performance of a skeletal muscle powered cardiac assist system. A chronically implantable temperature sensor is imbedded within the skeletal muscle. Muscle contraction and performance can be monitored by intramuscular temperature measurement. The temperature measurements are used by the implantable pulse generator of the cardiac assist system to maximize efficiency in the use of the skeletal muscle by optimizing timing of conditioning, maintenance, and stimulation pulses.

Abstract: A method of detecting inflammation of a nerve root adjacent to a spine of a patient using an ultrasound apparatus. The present method includes the steps of providing an ultrasound apparatus including an ultrasonic transducer interconnected with a source of electrical energy and with a receiver having amplification means, positioning the ultrasonic transducer on the patient's back in a location lateral to the spine, angling the ultrasonic transducer such that ultrasonic energy can be directed medialad to the spine, transmitting ultrasonic energy toward the nerve root at a power level and a frequency effective to create a reflection from an inflamed nerve root that is detectable by the ultrasound apparatus, and processing ultrasonic energy reflected from the nerve root. Ultrasound apparatus including ultrasonic transducers are also disclosed.

Abstract: Apparatus and method of controlling a muscle stimulator by varying the duty cycle. The muscle stimulator is particularly adapted to a skeletal muscle powered cardiac assist system. An activity or other sensor is used to determine the requirement for cardiac output. A second electrical sensor is used to determine the cardiac rate. The outputs of these two sensors are employed to select a duty cycle for muscle stimulation of the skeletal muscle. The duty cycle is lowered for reasons of efficiency and safety during periods of very high or very low cardiac rate or body activity. The number of stimulation pulses within a burst is similarly increased when cardiac demand is high to ensure maximum contractile force of the skeletal muscle during each stimulation burst.

Abstract: Apparatus and method for monitoring the performance of skeletal muscle used in a skeletal muscle powered cardiac assist system. The monitoring is performed by an oxygen sensor which determines the adequacy of circulatory support to the skeletal muscle. An adequately supported skeletal msucle can offer the desired cardiac assistance chronically. Insufficient support indicates that the skeletal muscle will easily fatigue until adequate vascularization is achieved. If the circulatory support is chronically insufficient, the risk of ischemia becomes high and additional surgical intervention may be required.

Abstract: Method of and apparatus for the treatment of angina pectoris using electrical stimulation within the epidural space of the spinal cord. A sensor is used to trigger stimulation only during periods of activity assumed to be symptomatic. The sensor may measure any of a number of parameters including blood oxygen saturation level or mechanical activity. In the preferred embodiment, a piezoelectric activity sensor is programmed to determine when the level of activity is reached at which angina is expected to occur in a particular patient. This determination is used to trigger an implantable pulse generator. Bursts of high frequency stimulation energy are applied by an insulated lead to electrodes implanted in the epidural space at an upper thoracic or lower cervical location. The increased neural activity caused by the stimulation bursts eliminates the pain sensation and allows an equal or higher exercise level of the patient without pain or at a similar pain level.

Abstract: An electrode and method of making same characterized by a biological material used as a substrate. The electrode is used primarily as a stimulation electrode, but could also be used to monitor electrical activity of neural tissues. The biological substrate is a chronically implantable material of treaterd human or animal tissue. The use of this material tends to prevent undue fibrosis and necrosis of the nerve tissue. An inner layer of a non-biologic dielectric may be used to increase to resistivity of the structure. Similarly an inner layer of shielding material may also be used.

Abstract: An apparatus and technique for electrical stimulation of the central or peripheral nervous system based upon changes in position of the patient. A position sensor may be chronically implanted in the patient. One preferred mode uses a mercury switch position sensor which indicates whether a patient is erect or supine. This position information is used by a chronically implanted pulse generator to vary the stimulation intensity. The intensity may be controlled by changes in pulse amplitude, pulse width, number of pulses per second, burst frequency, number of pulses per burst, electrode polarity, or any other convenient parameter which accomplishes the particular medical purpose within an application. The output of the chronically implanted pulse generator is applied to the spinal cord, peripheral nerves, and/or targets in the brain with leads and electrodes in a manner consistent with the given medical need.