American Optical Corporation

Siemens Medical Systems, Inc.

Siemens Aktiengesellschaft

Draeger Medical Systems, Inc.

Thomas K Naylor

Edwin Muz

Helen C Crouse

Scott W Newell

Clifford Mark Risher-Kelly

Clifford Mark Kelly

George A Cavigelli

Bernd Rosenfeldt

Charles LeMay

Edwin A Dokus

Michael Naylor, Legal Representative

Alan S Cushing

Helen Connelly Crouse

A cable detection system, includes a source of an input electrical AC signal for coupling to a first lead pin of a cable connector. A detector is coupled to a different second lead pin of the cable connector. The detector detects an electrical AC output signal derived by capacitive coupling of the input electrical AC signal occurring within a cable incorporating first and second leads corresponding to the first and second lead pins. The detector further enables a determination of whether the cable is connected to the cable connector in response to an amplitude dependent characteristic of the detected AC output signal.

Cable detection system

A shielded conductor path comprising: a first signal conductor having an input end for acquiring a physiological signal and an output end for coupling the physiological signal to a physiological signal input of a patient monitor, and a second signal conductor positioned with respect the first signal conductor for acting as a shield therefore. An inductance connected in series between an output end of the second signal conductor and the reference signal input of the patient monitor forms a filter circuit which attenuates the level of an interference signal in the second signal conductor. In one preferred embodiment of the invention, the inductance is part of an RLC filter circuit contained in a housing which is selectively insertable between an EKG lead set and the EKG signal input of a patient monitor. The selectively insertable filter permits the use of standard EKG lead sets in the presence of RF electrosurgery procedures, without risk of burning the patient at the site of the EKG electrodes.

Lead set filter for a patient monitor

A shielded electrical connector having an elongated annular housing composed of an electrically insulative material molded so as to form an elongated structure for the connector and at least a portion of a grasp for a user of said connector. The housing defines outside and inside surfaces and front and rear ends for said connector. A contact holding portion composed of an electrically insulative material is positioned inside said annular housing and includes a plurality of electrically conductive signal contacts positioned therein so as to be completely surrounded by, yet spaced a distance away from, the inside surface of the housing. An elongated annular electrically conductive shield having inner and outer sides is insert molded with the housing so as to be disposed between its outside and inside surfaces. The elongated shield has a proximal end adapted for being coupled to a common shield associated with the plurality of signal conductors and a distal end extending to and encapsulated by the front end of the housing, yet the front end of the housing leaving an unencapsulated portion of the inside surface of the shield which is spaced a predetermined distance away from the front end of the housing. The un-encapsulated portion of the inside surface of the shield is adapted for making electrical contact with a shield of a mating multi-conductor connector so as to provide an effectively continuous conductive shield which completely surrounds the electrically conductive signal contacts.

Fully insulated, fully shielded electrical connector arrangement

A flexible multi-parameter conductor cable having coaxially symmetric elongated zones for signal carrying conductor placement therein, comprising an electrically conductive inner shield defining an electrically shielded inner longitudinal zone symmetrically disposed along and defining a center of said cable for containing at least one of a first type of signal carrying conductor, and an electrically conductive outer shield spaced a given distance symmetrically around said inner shield so as to define an electrically shielded outer longitudinal zone symmetrically disposed about said inner longitudinal zone for containing a plurality of at least a second type of signal carrying insulated conductor arranged in a single layer adjacent one another in said second longitudinal zone, said second type of conductor having an electrically conductive outer jacket in electrical contact with at least said outer shield.

Flexible multi-parameter cable

A bank of differential amplifier circuits includes specialized circuits to provide multi-channel differencing with a minimum number of active devices such that the differences between pairs of analog input signals, such as available from patient monitoring electrodes, are derived with half the number of active devices normally utilized. In one embodiment, two operational amplifier circuits are used in a differencing channel which functions together to provide differencing, a properly delayed input signal for use in another differencing channel, high input impedance buffering, a low impedance output for each differential amplifier channel, time-coincident, matched outputs for each differential amplifier channel, and with an additional operational amplifier, a DC rejection circuit which does not affect the low output impedance or the differencing function, thereby to eliminate the necessity of providing separate buffers and active delay circuits which can result in the use of twice the number of active devices. The above results are accomplished through the use of a predetermined ratio for the input and feedback resistors associated with the pairs of operational amplifiers in each channel and by tapping off a signal in one channel for use as an input signal in another channel.

Apparatus for establishing the differences between multiple pairs of

The preamplifier comprises amplifying means, the output of which is inverted relative to the input, and a feedback circuit connected from the output to the input of the amplifier so as to provide a perfect integrator which cancels the amplitude variations resulting from changes in tape speed. The impedance of the feedback circuit and the impedance of the signal source extended to the amplifier are such that the output of the amplifier is the integral of the voltage generated in the inductive head over a wide band of frequencies.

Low-noise preamplifier

An input overload protection circuit particularly suited for use with a high impedance differential amplifier having two inputs is provided. The protection circuit prevents the flow of substantially all leakage currents for input signals within the linear operating range of the amplifier, and includes a first and second serial plurality of diode-action clamping means, such as diodes, connected respectively between the first and second input conductors to the amplifier input and a third conductor connected to a reference potential. Driven guard means operate to apply the voltage appearing on the respective first and second input conductors at their junction with the respective first and second clamping means to the respective first and second plurality of clamping means intermediate the respective ends thereof, thereby to substantially prevent leakage current from flowing through the clamping means from the pair of conductors.

Input overload protection circuit

In cardiac signal processing apparatus, there is provided improved means for suppressing pacer signal artifacts, including both the discharge pulse and the recharge waveform (tail) of such artifact. Rate-limiting circuitry is used to substantially suppress the discharge pulse. However additional circuitry responsive to the detection of a pacer pulse is operative to obtain a measure of the electrical discharge of the discharge portion of the respective pacer pulse and to use such measure to generate a tail suppression signal which, when added to the original signal, substantially cancels the original pacer tail. A feed-back loop is opened by the rate-limiter when a pacer pulse occurs and in turn permits a large signal to be imposed on a threshold-level-type pacer pulse detector for connecting the large signal (pacer pulse) to a capacitor during the discharge portion of the pacer pulse. The capacitor begins to discharge shortly after the pacer pulse's discharge portion with a polarity and time constant selected to substantially cancel (when summed) the pacer tail.

Pacemaker artifact suppression in coronary monitoring

An improved fast-recovery circuit for ECG amplifiers and the like. The fast-recovery circuit includes threshold responsive circuitry connected in parallel with part of the resistance associated with the integrator in a feedback circuit of the amplifier. The threshold responsive circuitry operates to increase feedback frequency response of the integrator when the normally very low frequency output signal of the amplifier exceeds a certain threshold. The improved circuit prevents the threshold circuitry from responding to pulses or excursions in the output signal of a relatively higher frequency content and which exceed the amplitude threshold for less than a predetermined interval, as for instance caused by pacer spikes, large QRS complexes and the like. Preferably, the improved threshold responsive means comprises transistor means connected across the integrator's resistance and having capacitance means across the base-emitter circuit thereof for inhibiting response to certain short duration signals.

Fast-recovery circuit

A DC isolation amplifier having improved conductive isolation between its input and output. The amplifier includes an input section having a modulator and an output section having a demodulator and an oscillator section. The modulator and demodulator are nonconductively coupled through inductive loops of two closed-loop cores of magnetic material each having windings inductively coupled to the material of their associated core and to the other of the modulator or the demodulator. Additionally, a unitary closed loop winding couples the two cores such that the net EMF induced in the turns of the winding accordingly such that the respective component of the external magnetic field of the turns is substantially normal to the respective plane of each turn of this plurality. Additionally, this unitary loop is twisted between the cores to comprise a twisted pair additionally to minimize the effects from external magnetic fields. In the preferred embodiment, this loop is limited to two turns per core. However, this number may be increased slightly for certain specific situations. In preferred embodiments, the cores are housed in magnetic shields, the shields having an opening in one end and the center line of the core is disposed in the plane of the opening of the shield.

Isolation amplifier

In an EKG monitor capable of monitoring the stimulation pulse of a heart pacer, the inclusion of means for determining the polarity of the pacer pulse detected in the ECG signal and then for generating a standardized pacer pulse signal of the same polarity as detected. The apparatus further includes summing means for summing the ECG signal with the standardized pacer pulse to be included in the output of the monitor.

Cardiac instrumentation apparatus with pacer diagnostics

There is disclosed a technique for compensating timing errors in low-speed tape systems, such as a system in which ECG signals are recorded on a tape moving as slow as 0.08 inches per second. Clock pulses are recorded on the tape together with the signal of interest. After the signal is derived during reading of the tape, the recorded clock pulses control the sampling of the signal. The samples are used to re-constitute the signal under the control of another set of clock pulses. This latter set of clock pulses is derived from the recorded set by a phase-locked loop which establishes equal time spacings between the re-constituting clock pulses even though the sampling clock pulses, which are read from the tape and applied to the input of the phase-locked loop, may have unequal time spacings.

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Belmont, MA, United States of America

Thomas K Naylor