Abstract: A controlled-power defibrillator and method of defibrillation for automatically compensating for changes in patient resistance during delivery of a defibrillation pulse. A switching power converter is connected between a storage capacitor and a pair of electrodes adapted for connection to a patient's body, either internally or externally. A closed-loop power control circuit is operatively connected to the power converter for control of the power delivered to the patient, the power control circuit generating a target voltage signal for the storage capacitor, the target voltage signal having a defined relationship with the waveform of the power desired to be delivered to the patient. The power control circuit monitors the actual voltage on the storage capacitor and adjusts the delivery of power to the patient as a function of the difference between desired and actual storage capacitor voltage.

Abstract: A tissue graft construct and method for repairing the inner linings of damaged or diseased vertebrate vessels is described. The method comprises the steps of positioning a tissue graft construct within a blood vessel at a site in need of repair. The tissue graft construct comprises a stent (3) covered with submucosal tissue (4) wherein the stent (3) is formed for receiving the distal end of a catheter (1) having an inflatable balloon (2).

Abstract: A tissue graft construct and method for repairing the inner linings of damaged or diseased vertebrate vessels is described. The method comprises the steps of positioning a tissue graft construct within a blood vessel at a site in need of repair. The tissue graft construct comprises a stent (3) covered with submucosal tissue (4) wherein the stent (3) is formed for receiving the distal end of a catheter (1) having an inflatable balloon (2).

Abstract: A closed-loop, variable-frequency, vagal-stimulation apparatus for control of ventricular rate during atrial fibrillation. In one embodiment the apparatus includes a stimulator applied to the left vagus nerve and a controller programmed to automatically and continuously adjust the vagal stimulation frequency as a function of the difference between actual and desired ventricular excitation rates. In a second embodiment the apparatus includes a vagal nerve stimulator and a controller which automatically adjusts the vagal stimulation frequency as a function of the difference between ventricular excitation rate and arterial pulse rate in order to eliminate or minimize pulse deficit.

Abstract: A closed-loop variable frequency vagal stimulation apparatus for control of ventricular rate during atrial fibrillation. In one embodiment the apparatus includes a stimulator applied to the left vagus nerve and a proportional controller programmed to automatically and continuously adjust the vagal stimulation frequency proportionally as a function of the difference between actual and desired ventricular excitation rates. In a second embodiment the apparatus includes a vagal nerve stimulator and a controller which automatically adjusts the vagal stimulation frequency as a function of the difference between ventricular excitation rate and arterial pulse rate in order to eliminate or minimize pulse deficit.

Abstract: Cardiac output is measured using an injected substance (indicator) that changes the conducting property (electrical resistivity) of blood, provided the indicator has a different resistivity from that of blood. A new type of electrically compensated tetrapolar conductivity cell located at the distal end of an intravascular catheter is disclosed. The conductivity cell consists of four electrodes arranged across the end of a catheter at its tip. The outer electrodes used for current injection are enlarged to reduce the electrode-electrolyte interface impedance. Capacitance compensation of the cather/tetrapolar conductivity cell provides reliable and repeatable blood resistivity measurements. The catheter further includes a calibration resistor thereby eliminating a calibration step previously necessary in using such a catheter for measuring cardiac output.

Abstract: A capacitive measuring pad is constructed of transverse conductive strips separated by a compressible insulator to form a matrix of pressure sensitive capacitive nodes. The nodes are repetitively scanned in sequence by a microcomputer to measure their respective capacitances, from which measurements a pressure map is then derived. The resulting pressure map may be displayed on a color graphics monitor with different colors representing diffrent pressures. Node capacitance is found by measuring the response of the mode to a driving signal of a known voltage. This measurement is accomplished by connecting one of the node's transverse conductive strips to the driving source and the node's other conductive strips to a sense amplifier. In order to isolate the node of interest from the influence of surrounding nodes, all of the conductive strips except the two intersecting the selected node are connected to ground.

Abstract: Method and apparatus are disclosed for thermally destroying a layer of an organ such as the mucosal layer of the gallbladder. The apparatus includes a catheter having an elongated member having a plurality of lumens therein. At the distal end of the elongated member is an electrode for emitting radiofrequency current to the mucosal layer. Also at the distal end is a capacitive balloon electrode surrounding the current-emitting electrode for containing an electrolyte solution and for distributing the radiofrequency current to the mucosal layer. The balloon electrode is expanded with the electrolyte solution to conform and make contact with the mucosal layer. The electrolyte solution has a resistivity significantly less than the resistivity of the gallbladder wall, as well as the gallbladder bile, to cause a concentrated power deposition in the mucosal layer.

Abstract: A demand electroventilator for monitoring and stimulating the respiration of a patient operates in a manner analogous to the operation of a demand cardiac pacemaker for monitoring and stimultating the heart when needed. The demand electroventilator has a pair of stimulating electrodes for placement on the chest of the patient and a pair of monitoring electrodes for placement on the patient's chest. The demand electroventilator also has a monitoring module connected to the monitoring electrodes, a stimulating module connected to the stimulating electrodes and a control module connected to the stimulating and monitoring modules. The monitoring module generates a signal related to the respiration of the patient which the control module interprets and causes the stimulating module to apply a train of electrical pulses having durations of 0.1 msec or less to the patient to stimulate respiration when needed.

Abstract: A pressure distribution measuring system includes a pad of insulating material disposed between two linear arrays of electrodes to form a matrix of capacitive nodes. A capacitance related output signal that is obtained from a node of interest is used as a feedback signal and applied to other capacitors that are connected in common with the node of interest. The feedback signal inhibits the flow of current through these commonly connected capacitors, and thereby isolates the measured signal from any changes in the capacitance of these other capacitors. The pad includes a cental array of linear electrodes sandwiched between two layers of dielectric foam material. Two outer, aligned linear electrode arrays, oriented perpendicular to the central array, are respectively disposed on the outside surfaces of the dielectric layers. In a preferred form, alternating electrodes in each outer array are located on opposite sides of a support substrate.

Abstract: A method of controlling cardiac ventricular fibrillation and other tachyarrhythmias. A catheter carrying a first and second electrode is located in the right ventricle such that the first electrode is located in the right ventricle and the second electrode is located in the superior vena cava. A third electrode is located either at the chest wall or at the abdominal cavity. The third electrode can be implanted subcutaneously in the left chest wall. It can also be located in the abdomen immediately beneath the diaphragm. It could also be implanted in the epigastric area overlying the superficial abdominal muscles and underneath the skin and fat. The second and third electrodes are sequentially paired and pulsed with the first electrode to control ventricular fibrillation and other tachyarrhythmias.

Abstract: A method of controlling cardiac ventricular fibrillation and other tachyarrhythmias by delivery of two time-separated current pulses to separate pairs of electrodes spatially placed in, around, or on the heart. The technique produces a temporal and spatial summation of the delivered current, which results in a dramatic reduction in the voltage, current, and energy required for defibrillation, or cardioversion, and allows the use of a smaller implantable pulse generator. The new system achieves a more uniform distribution of current within the ventricular myocardium, thereby reducing the risk of tissue damage and increasing the margin of safety between effective shocks and myocardial depressing or damaging shocks.

Abstract: Apparatus and method for measurement and control of blood pressure are disclosed. Blood pressure is indirectly continually monitored without use of a pressure transducer by sensing the pulse transit time to different sites in an artery, which transit time is inversely related to blood pressure, and developing pulses therefrom which are utilized to form arterial pulse waves, the comparison between which provide an indication of measured blood pressure. This indication is used to control blood pressure by controlling automatic release of a suitable drug into the body in amounts and over a time period as needed. The unit for measuring blood pressure includes two sets of electrodes positioned adjacent to but outside an artery at two sites (with the electrodes implanted or outside the body).

Abstract: An electrosurgical dispersive electrode is disclosed that is useful in conjunction with an electrosurgical unit to establish capacitive-coupling with the skin of a patient receiving therapeutic signals from the electrosurgical unit. The electrode includes a metallic plate electrically connectable with the electrosurgical unit to establish a return current path thereto, an insulator engaging the inner (patient) side of the metallic plate to prevent ohmic contact by the plate with the skin of the patient, and a conductive adhesive gel at the outer (patient) side of the insulator so as to be positioned between the insulator and the skin of a patient to bring the skin uniformly in contact with the gel conductor and thereby reduce the impedance, normally associated with capacitively-coupled dispersive electrodes, while retaining uniform temperature distribution.

Abstract: Method of and apparatus for automatic defibrillation of the cardiac ventricles of a heart wherein both the mechanical and electrical activities of the ventricles are sensed and used as operating inputs to the controls. Electrical activity is detected and measured with a pair of electrodes, and the waves of an electrocardiogram (ECG) are analyzed. When such electrical analysis indicates that ventricular fibrillation is present and persists, an electrical circuit is actuated for detecting mechanical pumping activity of the heart. Mechanical pumping activity is measured by the change in impedance between the pair of electrodes in one of the ventricles. The change of ventricular impedance is caused by the varying volume of blood contained within the ventricle and depends upon whether the ventricle is in a contracted or a relaxed state. The defibrillator is actuated only when both the mechanical and electrical activity of the ventricle indicates a need for defibrillation.

Abstract: A demultiplexing method and system is disclosed utilizing a differential duration technique. Data that have been conventionally encoded utilizing a technique wherein variations in time contain the essential information, such as can be accomplished by systems wherein data are encoded by modulating either the spacing between pulses or the width of the pulses, is decoded by differential duration demultiplexing to reduce errors caused by time distortion introduced prior to recovery of the data. Time distortion errors are reduced by sensing both the pulses and intervals following the pulses in the data train and deriving decoded data from the difference therebetween.