Abstract: An auditory prosthesis includes a sound sensor that senses both ambient sounds and sounds uttered by the patient. The prosthesis includes a monitor that senses a physiological parameter indicative of the intensity of the sounds as perceived by the patient and/or the onset of a prospective speech episode during which the patient utters sounds. For example, the monitor may detect the activity of the stapedius muscle. This muscle contracts in the presence of subjectively perceived high level sounds or just prior to and during a speech episode. This parameter is used dynamically by the prosthesis to process the received sounds, for example, by changing the amplification level of these sounds dependent on the activity.

Abstract: A cochlear implant system includes an electrode array (1) comprising multiple platinum ring electrodes in a silastic carrier to be implanted in the cochlea of the ear. A receiver-stimulator (3) containing a semiconductor integrated circuit and other components is implanted in the patient adjacent the ear to receive data information and power through tuned coil (5) using an inductive link (6) from a patient-wearable external speech processor (7) including an integrated circuit and various components which is configured or mapped to emit data signals from an EPROM programmed to suit each patient electrical stimulation perceptions through testing of the patient and his implanted stimulator/electrode using a diagnostic and programming unit (12) connected to the processor by an interface unit (10).

Abstract: There is disclosed a bridge circuit which finds particularly advantageous use in medical prostheses which can be programmed externally and which can transmit telemetry signals. The entire circuit is implemented on a single CMOS integrated circuit. Depending upon the values of two control bits, the bridge circuit functions to derive a powering potential from an externally transmitted signal, with or without regulation. Externally transmitted programming signals are detectable, and telemetry signals can be transmitted from the chip as well. There is no active switching of bridge devices during power rectification mode, and instead they are biased on continuously. This allows the rectifier to operate at carrier frequencies as high as several megahertz. All of this is achieved by using conventional CMOS processing techniques, without requiring any extra diffusion steps.

Abstract: A delta modulator for controlling time-domain processing of sensed signals, and particularly internal physiological signals. The delta modulator includes two constant current sources both of which are on continuously, but only one of which is connected to the input capacitor at any given time. The two constant current sources are self balancing. Periodically, the two current sources are connected simultaneously to a control capacitor, the potential across which is thus a function of the relative current source amplitudes. The potential across the control capacitor is used in a feedback circuit to control the amplitude of at least one of the current sources so that the two sources are made to have equal amplitudes. Preferably, the control capacitor is an on-chip capacitor whose effective capacitance is increased by the Miller effect.

Abstract: A test system for a sealed, sterile package containing a cochlear prosthesis electrode. A light-emitting diode has its two leads in contact with at least two different conducting bands on the electrode. The prosthesis, which is externally-powered, is operated so as to supply a stimulus current between the two bands. If the light-emitting diode is illuminated, proper operation of the prosthesis can be verified without unsealing the package.

Abstract: A fast-operating, minimally complex circuit for automatically clamping the P wells of a CMOS integrated circuit to the most negative potential of the overall circuit. Each of a plurality of N-channel control transistors has its drain connected to a respective one of the circuit nodes whose potential may be the most negative at any given time. The source terminals of all of the control transistors are coupled to a common negative supply bus which is connected to all of the P wells in the integrated circuit. The gates of all of the control transistors are held at a potential which causes them to conduct drain-to-source current. If one of the nodes suddenly drops in potential, the respective control transistor conducts a current in the reverse direction which lowers the potential of the common bus to approximately the potential of the respective node. The respective control transistor conducts heavily until the common bus is thus clamped, and then conducts just enough current to maintain the clamping.

Abstract: The signal sensed on a heart pacer electrode is converted by a delta modulator to a sequence of samples of 0 and 1 bit values. The resulting bit sequence is delayed, and the original bit sequence and its delayed version are continuously subtracted from each other in a clocked up/down counter to derive a count. When the count reaches a threshold value, three different recognition logic circuits are triggered and they then operate for two milliseconds. One circuit recognizes a beat if the count does not drop below another, lower threshold value during the timing interval. A second circuit detects a beat if the count remains above the threshold level for at least 50% of the time during the timing interval. The third circuit detects a beat by operating directly on the delta modulator output bit sequence; it checks whether bits of the value indicative of the triggering event predominate over bits of the opposite value during the timing interval.

Abstract: There is disclosed a heart pacer in which the sensed signal is processed in the time domain rather than the frequency domain. A delta modulator operates directly on the sensed electrogram signal, without any intervening filtering, to derive a sequence of bits whose states represent increments or decrements in the sensed signal amplitude. Decisions as to cardiac activity are based on the sequence of bit values thus generated. The particular delta modulator disclosed is highly advantageous in that it allows highly accurate tracking and representation of the sensed signal.

Abstract: A transmitter for a medical prosthesis which is highly efficient, and also permits rapid starting and stopping so that the same coil can be used for both transmission and reception without undue delays between the two modes of operation. During transmission, a tuned circuit, consisting of the coil and a capacitor, is pumped at a frequency equal to the resonant frequency. Transmission is concluded when almost all of the energy in the tuned circuit is in the form of a voltage across the capacitor and when the current through the inductor is approximately zero. This allows the inductor to be used immediately for reception. At the start of the next transmission cycle, the voltage which is maintained across the capacitor is used to initially energize the tuned circuit.

Abstract: A delta modulator for a heart pacer which not only allows sensed signals to be monitored, but also facilitates measurements of DC operating potential levels. The DC levels, and changes in them, can be measured accurately by equilibrating the modulator with the application to it of a suitable reference potential as the initial step in a measurement sequence. This same technique allows small signal variations to be tracked even if they are superimposed on large signals.

Abstract: A heart pacer in which the magnitude of the end-of-life test current source is programmable. This effectively allows the physician to program the condition which will control a switch-over to end-of-life operation. It also allows the physician to override end-of-life operation after it initially takes place following a failing of the end-of-life test. The pacer also includes an additional end-of-life test involving the continuous monitoring of the supply potential and a switch-over to end-of-life operation should the pacer powering potential momentarily fall below a threshold level.

Abstract: There is disclosed an implantable bone growth stimulator whose direct-current output can be monitored. Rather than to interrogate the device, e.g., by using a control magnet as in the heart pacer art, the device continuously transmits pulses of electromagnetic energy at a rate proportional to the current being delivered. The continuous transmission expends no more than about five percent of the total power. Instead of using an electrode lead as an antenna for radiating the pulses, a separate coil inside the device is utilized so that the therapeutic current itself is in no way affected by the pulse transmission. Effective transmission is achieved despite the fact that the device is hermetically sealed in a titanium case. Also included is an electronic switch for drastically limiting power drawn from the battery until implantation takes place, in order to provide an extended shelf life.

Abstract: There is disclosed an implantable tissue-stimulating prosthesis, such as a cochlear prosthesis, which can not only be implemented in single-chip form, but which also permits great flexibility in stimulation strategy and data transmission format. Only sixteen electrodes are required for stimulating fifteen different sites. Each site is stimulated by a biphasic pulse under control of two adjacent electrodes whose polarities are reversed in the middle of the site stimulation cycle. Although the transmission scheme requires a pulse-width modulation format, the precise form of the format can be varied in order to accommodate widely different stimulation strategies. For example, only a single site may be stimulated during each transmission frame or multiple sites may be stimulated during the same frame. Although only one site can be stimulated at any instant of time, the system cycling is so fast that "simultaneous" site stimulations are perceived.

Abstract: A porous cardiac pacemaker electrode comprising a concavo-convex electrode cap having a plurality of apertures therethrough and an electrode shaft having a supporting edge formed thereon to which the concave surface of the electrode cap is joined. The porous cardiac pacemaker electrode is produced by deforming a platinum plate into a concavo-convex shaped cap member, forming a plurality of selectively spaced apertures through the electrode cap member to make the electrode cap substantially porous, forming an electrode shaft having a supporting edge, and joining the supporting edge of the electrode shaft to the concave surface of the electrode cap member.

Abstract: There is disclosed a direct-coupled output stage which is especially advantageous for use in an implantable heart pacer. In order to provide for charge balancing at the electrode/electrolyte interfaces, the electrodes are shorted to each other after a pacing pulse is generated. Not only is the use of a bulky coupling capacitor avoided, but the stored charge dissipates in a much shorter time, thereby minimizing the "blind" interval in the sensing cycle.

Abstract: There is disclosed a dual chamber pacer which offers several advantages over prior art devices. Although the pacer requires for its operation AV delay and VA delay parameter values, most physicians characterize dual chamber pacers in terms of AV delay and ventricular pacing rate. The pacer of the invention can be programmed under external control by the physician setting values for the parameters with which he is most familiar. A subtractor in the pacer forms the difference between the reciprocal of the ventricular pacing rate and the AV delay to derive the value of the VA delay. The pacer is also characterized by active recharge of the atrial output capacitor so that a very short ventricular refractory period following atrial pacing may be provided. A single maximum rate timer prevents the generation of excessively fast ventricular stimuli, whether due to the ventricular or atrial sub-systems, or even if atrial contractions are being sensed at too rapid a rate.

Abstract: A pacer which facilitates the measurements of both electrode impedance and stimulation threshold. When activated by an external magnet, a sequence of reducing-amplitude stimulating pulses is generated, with successive pulses in the sequence being separated by full-amplitude pulses. This pulse alternation scheme allows long test sequences, and therefore measurements with greater resolution, because full-amplitude pacing pulses are always present (even though at a slightly reduced rate). The reduction in amplitude of successive pulses is determined by the electrode impedance rather than being predetermined, and thus the examination of a skin potential recording allows electrode impedance to be determined along with the capture threshold.