Abstract: A non-programmable automatic implantable cardioverter/defibrillator (AICD) capable of providing programmable thresholds for triggering high energy stimulation pulse(s) from the AICD is coupled to an implantable programmable pacemaker which preferably includes bradycardia support and/or tachycardia support using low enery output pulses. When the low energy antitachycardia pulse(s) from the pacemaker fail to terminate a tachycardia, or whenever other various thresholds, as sensed by programmable sensing circuits of the pacemaker, are exceeded, the high enery pulses from the AICD may be selectively invoked by an AICD trigger circuit included within the pacemaker. Coupling between the AICD and pacemaker is by either a direct electrical connection, or by an indirect connection, such as through the use of narrow pulse sequences generated by the pacemaker which are of insufficient energy to invoke a cardiac response but are of sufficient energy to be sensed by the AICD sensing circuits.

Abstract: A communication system includes self-test means for automatically testing its performance. The communication system is adapted for use between an implantable device, such as a pacemaker, and an external device, such as the pacemaker's programmer. The communication system includes in the external device a transmitter circuit for transmitting an output signal through an antenna, and a receiver circuit for receiving an input signal through an antenna. A driver circuit controls the operation of the transmitter circuit. A microprocessor, connected to the driver circuit, controls the information content and timing of the transmitted output signal. A bandpass filter and AM demodulator process the input signal received through the receiver circuit. A multiplexer selectively allows one of a plurality of status signals from throughout the communication system within the external device, including the demodulated signal obtained from the AM demodulator, to be connected to the microprocessor.

Abstract: A self-oscillating burst mode transmitter transmits an integral number of cycles of a carrier signal in each transmission burst. Each burst commences at a peak value of the carrier signal and terminates at a peak value. The transmitter includes an L-C tank circuit comprising a transmitting coil (L1) connected to a capacitor (C4). The L-C tank circuit is selectively energized through a switching network (Q1, Q2, U1, U2) connected to a power source, causing the tank circuit to resonate at a prescribed frequency (f.sub.0). Selective energization of the tank circuit is achieved by the switching network as controlled by a peak voltage detection circuit (32, 34). The peak detection circuit senses when a peak voltage is present in the oscillatory waveform appearing across the coil of the resonating tank circuit. Power is switched off to the tank circuit at the conclusion of each transmission burst only when the oscillatory voltage waveform, as sensed by the peak detection circuit, is at a peak.

Abstract: A device for use as a self-oscillating Class D transmitter is disclosed which uses feedback to maintain the oscillation at the resonant frequency of the device, thereby optimizing the efficiency of operation and overcoming the frequency mismatching inherent in previously known transmitters. The device uses a series LC combination which is driven by a comparator and a tri-state logic driver, with a feedback loop using a differentiator used to switch the polarity of the square wave generator. The system thus self-oscillates at the resonant frequency of the capacitor and inductor, even when the inductance of the inductor is varied by the inductor coming into close proximity to another inductor.

Abstract: A system for detecting an occlusion in a fluid line is disclosed which can detect occlusions in the upstream or container side of a disposable cassette containing a fluid pump therein. The cassette includes a piston-type pump with inlet and outlet valves, and is for installation onto and use with a main pump unit including motors for driving the pump and valves contained in each cassette. The system utilizes control circuitry to monitor the intake stroke of the pump in the cassette, to detect an upstream occlusion in the fluid line leading to the pump, and to provide an alarm in the event of a container-side occlusion.

Abstract: A method of significantly enhancing the period of time that an implanted intraperitoneal catheter used for the delivery of therapeutic medication will operate without encountering significant blockage by fibrotic tissue is disclosed. By monitoring and maintaining certain physical parameters in patients having an implantable catheter below desirable levels for the parameters, catheter survival in the patients is maximized. The four parameters used are blood triglyceride level, blood cholesterol level, the level of insulin dosage per day, and mean blood glucose (MBG) level, with the first two being the more accurate parameters.

Abstract: A digital phase-locked looped generates a clock signal synchronized with a carrier signal modulated by amplitude shift keying (ASK). During periods when no carrier signal is present, the generated clock signal coasts at the frequency of the carrier signal most recently present, rather than trying to phase-lock on noise. A binary controlled digital oscillator generates the clock signal. A phase detector determines the difference between the phase of the carrier signal, when present, and the local clock signal. When the average amplitude of the carrier signal exceeds a prescribed threshold level, the phase detector output is sampled and passed to an integrator circuit, where the phase difference is integrated. The output of the integrator circuit is applied to a pulse generator, causing the pulse generator's duty cycle to change proportionally.

Abstract: An atrial rate based programmable pacemaker including means for preventing the heart from being paced at an upper rate limit for prolonged periods of time is disclosed which paces the heart at a rate that follows or tracks the atrial rate up to the upper rate limit of the pacemaker, at which point the pacemaker stimulates the heart at the upper rate limit, but also continues to monitor the atrial rate. If the monitored atrial rate exceeds a second upper rate limit, a fast atrial arrhythmia or tachycardia condition is deemed to exist, and the pacemaker automatically switches from its existing mode of operation to an alternate mode of operation in an attempt to break or terminate the fast atrial condition. Alternate embodiments include using an external activity or physiological sensor to control the pacing rate in the new pacing mode, and the inclusion of means for periodically verifying that atrial sensing is occurring, and means for automatically adjusting the sensitivity of the atrial channel as required.

Abstract: A high speed digital telemetry system (10) includes a transmitter (12) and a receiver (14), at least one of which is adapted for use in an implantable device. The transmitter includes a data encoder (14), modulator (16), transmitting coil (20), and transmitting coil drive circuit (18). The data encoder examines prescribed incoming data bits and prior encoded data bits, generating an encoded data stream (36) that includes a data transition only when a prescribed correlation is noted amongst the examined bits. The modulator modulates a carrier signal (34) with the encoded data stream, causing a phase reversal of the carrier at each data transition of the encoded data stream. The transmitting coil drive circuit applies the modulated carrier (38) to the transmitting coil. The receiver includes a receiving coil (22) and associated amplifier (24) and bandpass filter (26) for detecting the transmitted modulated carrier.

Abstract: A rate-responsive pacemaker which includes a conventional programmable pulse generator, a physiological sensor, and a processor is disclosed which generates heart stimulation pulses on demand, or as otherwise programmed, as controlled by a rate control signal which is derived from the physiological sensor. The physiological sensor generates a raw signal which varies as a function of some physiological parameter, such as activity level to provide some indication of whether the heart rate should increase or decrease, and hence whether the pacemaker should change the rate at which pacing pulses are provided. The processor converts the raw signal to the sensor-indicated rate signal in accordance with a selectable transfer relationship which defines the sensor-indicated rate signal as a function of a set of discrete sensor level index signals.

Abstract: A unitary piston cap and boot seal for use in a medication infustion system is disclosed which is mounted on a rigid piston contained in a cylinder disposed in a cassette. The piston cap and boot seal, which are made of a flexible, elastomeric material, effectively both form the pumping element disposed in the cylinder, and prevent contamination of the pump through use of a rolling seal. The device may be sterilized by gas, since a tortuous path affording passage to gas is included in the retaining skirt mounted around the outer diameter of the pump cylinder.

Abstract: A device for use as a rate-responsive pacemaker is disclosed in which the pacing interval is controlled by the amount of energy contained in a raw signal generated by a suitable physiological sensor and processed by an energy converter to generate an output energy signal coupled to the pacemaker control circuits to adjust the pacing interval. The energy converter may be a rectifying amplifier and an integrating circuit, a voltage controlled oscillator whose frequency is measured over a suitable time interval using a time interval generator and a counter with the output of the counter being used by the control circuits of the pacemaker to vary its pacing interval, or means for measuring energy content of the raw signal and storing that measurement in memory and periodically processing it to alter the transfer characteristics of the rate-responsive pacemaker.

Abstract: A fluid delivery monitoring and control apparatus for use in a medication infusion system is designed for use with a disposable fluid pathway that incorporates a sterile cassette containing pumping elements and sensor interfaces. The apparatus comprises a multi-segment drive mechanism, controller, and monitoring system. Fluid pumping is accomplished by controlling DC motors in the drive mechanism, each of which is coupled to two valves and a reciprocating piston for an individual pumping channel in the cassette. The motor is geared down to provide an appropriate maximum speed and torque. A cam sequentially actuates an inlet valve, piston, and an outlet valve in the cassette. A range of fluid delivery rates is achieved by periodically sending pulses to the motor. The output flow rate of the pump is maintained by a digital feedback controller which uses closed-loop feedback control to provide accurate regulation.

Abstract: A method of screening potential recipients of an implantable medication infusion system including an implanted intraperitoneal catheter is disclosed which seeks to select only those candidates who will have a high degree of resistance to catheter blockage due to fibrotic tissue growth. By checking certain physical parameters in candidates for an implantable catheter, and by declining to implant in those candidates who have higher than desirable levels of the parameters, catheter survival in those patients chosen for implant is maximized. The four parameters used are blood triglyceride level, blood cholesterol level, the level of insulin dosage per day, and mean blood glucose (MBG) level, with the first two being the more accurate parameters.

Abstract: A pacemaker lead analyzer for measuring impedance during standard operation of an implanted pacemaker. The analyzer makes separate measurements of lead impedance during each heart signal and each pacing pulse. A moving average of measured parameters is maintained and recurring deviations from the norms are noted in separate event counters for subsequent analysis of the noted events as possible indications of impending failure of an implanted lead.

Abstract: An adjustable template device for pacemaker ECG analysis is similar to a slide rule with a transparent window portion which can be laid over an ECG trace to aid in its analysis. A frame for the template has a back member and a cover member connected together with rivets, with the cover member having cutout portions through which various scales printed on the back portion can be seen. A series of movable transparent plastic sheets slide back and forth independently in the frame to allow measurement of time intervals on the ECG trace. Fiducial marks on the movable sheets indicate time intervals by their positions with respect to scales on the back member. AV, AE, MT, PVAR, and pacing intervals can all be set simultaneously on the template. A photocopy of the template overlying the ECG trace can be made to provide a permanent record.

Abstract: A device for use to detect air in a fluid line between a medication infusion reservoir such as an IV bottle or bag and an IV injection set or a medication infusion pump is disclosed which utilizes a detector apparatus which clamps onto a segment of tubing. The detector uses a light source to generate light which is directed into the tubing, and two light detecting devices, one of which is used to determine whether or not the tubing is properly installed in the detector, and the other of which is used to detect the presence of air in the segment of tubing. The detector works equally well with transparent, translucent, or opaque fluids and includes means for ensuring that the detection system is functioning normally.

Abstract: A cassette identification system for use with a medication infusion system having disposable cassettes which are mounted onto a main pump unit is disclosed which uses an optical sensor module to read the identifying bits from the cassette. The identification indicia contained on the cassette each either pass light through a portion of the cassette, or diffuse the light to prevent it from passing through the cassette. The optical module is mounted on the main pump unit, and includes light sources and sensors for each of the identification indicia on the cassette; the system may use either redundant or non-redundant coding for identifying the cassettes.