Abstract: In a defibrillator/monitor having first electrodes for applying the defibrillating signal and second electrodes for monitoring physiological conditions and switch means for connecting the active leads to the defibrillator monitor through an isolation amplifier the inclusion of additional isolation amplification means intermediate the defibrillating electrodes and the switch means to prevent current leakage between the two electrode systems during the application of the defibrillating signal.

Abstract: In a blood pressure measuring system in which a pressure signal comprised of both applied pressure and pulsatile pressure is detected and subsequently filtered to separate the pulsatile pressure component, circuitry is provided to minimize start-up transients in the separated signal. Such start-up transients, which normally persist for some time after start-up as a result of the AC time constants of the filters, are otherwise capable of generating erroneous measurements. The circuitry initializes the filters by clamping their outputs to predetermined voltage levels during a start-up interval and thereby avoids the generation of the transients.

Abstract: In heart monitoring systems for use with patients whose hearts may be stimulated by an artificial pacer and which system includes heart rate indicating means, there is provided circuitry for suppressing the recharge waveform portion of a pacer signal artifact in addition to suppression of the discharge pulse portion of the signal artifact, thereby to prevent inaccuracies in the heart rate indication arising from the pacer signal artifact. In addition to suppressing the discharge pulse portion of a pacer signal artifact with conventional means, the invention recognizes that the recharge waveform of the pacer signal may cause a false impression of a QRS complex which actuates heart rate indicating means and provides novel circuitry for suppressing such recharge waveform.

Abstract: In an implanted heart stimulating device of the demand type, test mode circuitry is arranged to cause the temporary generation of stimulation impulses at the demand-rate in the presence of naturally occurring heartbeats. The test mode circuitry may cause dependence of the heart-stimulation rate upon the level of the power source within the test mode or at least a portion of the test mode, but is arranged to provide a heart-stimulation rate independent of the level of the power source in the ordinary demand mode. The test mode circuitry is operative, through a relatively simple bias-modifying circuit, to force the pacer to generate at least several stimulating impulses at the demand-rate immediately following cessation of that portion of the test mode in which stimulation impulses are generated at a rate dependent upon the level of the power source. Subsequently, the pacer reverts to the ordinary (i.e., non-forced) demand mode.

Abstract: A system for the enhanced display of event markers in time-related association with physiological waveforms displayed on cathode ray tubes which use a recirculating memory to provide a refreshed display. The event is marked in the displayed waveform by an intensification of the normal trace determined by the time-related occurrence of the event and comprises a first modulation of the displayed waveform. A secondary event-controlled modulation of the primary modulated display serves to further enhance and accurately identify the occurrence and timing of the event marker in the display. This enhanced display of event markers is further utilized to distinguish a marker of one type from a marker of another type utilizing particular data coding in the memory and appropriate detection logic for recovering data from memory. The enhanced display is particularly useful for clearly marking events occurring in timed-relationship with a patient's cardiac cycle.

Abstract: The refractive power(s) of a lens which may possess cylindrical power are determined by retro-reflecting a particular target image through an optical system and varying the axial positioning of one or more elements in the system to bring the reflected image to one or two clear and unambiguous foci at a target plane. By employing a small, intense diffraction image as the target image and further detecting only reflected light passing through a pinhole area on the optical axis at the target plane, a single significant light energy peak is observed at system focus for a lens possessing sphere power only and two significant light energy peaks appear at the respective foci of the principal meridians if the lens also has cylinder power. Means are provided for recognizing the existence, number, and/or relative size of light energy peaks and for correlating their occurrence with the position of the movable element in the optical system to determine respective refractive powers of the test lens.

Abstract: A battery-connection system for a battery having a pair of battery terminals of opposite polarity and positionable in either of two reversed positionings relative to distribution means. The distribution means includes a pair of spaced electrical terminals of particular and opposite polarity electrically connected with a unit to be powered. A carrier interpositioned between the battery and distribution means including a first pair of electrical contacts in singularly-polarized electrical contacting engagement with the respective battery terminals and a second pair of spaced electrical contacts electrically connected with respective ones of the first pair of contacts for singularly-polarized electrical contacting engagement with the respective pair of distribution means terminals. Each contact of the carrier second pair is of opposite polarity to the other, and comprises a set of plural alternate contacts of the same polarity.

Abstract: An isolation amplifier comprising three separate conductively-isolated sections: (1) an input section including an AC modulator, (2) an output section including a demodulator, and (3) an improved oscillator or AC power section for reducing the undesirable effects of common mode interference signal sources coupled thereto through stray capacitance. The improved oscillator or power portion includes control elements for controlling the timing and direction of current conduction through the primary winding of a transformer having its secondary connected to the chopper or modulator. The control elements and circuitry associated therewith conduct in alternation and in a manner resulting substantially in conduction-overlap. Such conduction overlap is accomplished by means which accelerate initiation of conduction in one control element and possibly also retard the cessation of conduction in the other control element.

Abstract: A conventional pressure cuff is attached to a living test subject. First means are provided for changing pressure in the cuff and thereby applying pressure to the subject. Second means communicating with the cuff are provided for measuring a quantity proportional to a time-dependent fluctuating component representative of pulsatile pressure within a blood vessel of the subject, the second means having a frequency response adequate to accurately follow the subject's blood pressure waveform, for instance at least about five times the subject's pulse rate, whereby the fluctuating quantity is proportional to amplitude of pulsatile pressure. The maximum value of the fluctuating quantity is determined as applied cuff pressure is changed.

Abstract: A razor blade assembly which is flexible in at least one bending mode. A seat member of substantially planar shape has an integrally formed guard located transversely along its forward margin. The guard and seat members are formed of a flexible material. A flexible blade having a sharpened edge along a transverse margin is disposed on a surface of the seat member having its edge parallel to and rearwardly located of the guard bar. A cap member of flexible material has a planar surface in contact with the blade and a front margin located rearwardly of the cutting edge. The seat, blade and cap are yieldingly bonded together and freely flexible about an axis parallel to the plane of the blade and perpendicular to the cutting edge.

Abstract: A flexible fiber optic probe or catheter insertable into the cardiovasular system for monitoring blood oxygen saturation or the like is provided with an improved standard for the calibration of the catheter and its associated electro-optic equipment. The improved calibration standard is particularly suited for catheters of very small diameter, is provided by a generally tubular reflecting member aligned with and adjacent to the distal end of the catheter. The reflecting member may be vinyl tubing or the like which may be removably of fixedly positioned about the distal end of the catheter to reflect light directed thereon from the catheter when in air or a clear sterile solution for calibration.

Abstract: An improved graphical recorder display system for obtaining an accurate record of one or more sensed and displayed parameter values, such as associated with one or more vital signs of a patient.

Abstract: A conventional pressure cuff is attached to a living test subject. First means are provided for changing pressure in the cuff and thereby applying pressure to the subject. Second means communicating with the cuff are provided for measuring a quantity proportional to a time-dependent fluctuating component representative of pulsatile pressure within a blood vessel of the subject, the second means having a frequency response of at least about five times the subject's pulse rate, whereby the fluctuating quantity is proportional to amplitude of pulsatile pressure. The maximum value of the fluctuating quantity is determined as applied cuff pressure is changed. Third means are provided for determining when the fluctuating quantity is about one-half its maximum value for applied cuff pressure greater than the pressure applied when the maximum value occurred or resulted.

Abstract: A circuit for use with an oximeter system which provides constant current pulses to light-emitting diodes in a sequential and cyclical manner. The circuit maintains magnitudes of pulses in the pulse train equal to certain other pulses in the pulse train over extremes of temperature variation, voltage variation, and time duration. Each diode is energized by a series of pulses having the same magnitude, although pulse magnitudes will vary from diode to diode. Therefore, light output from one light-emitting diode remains proportional to light output from the others.

Abstract: There is disclosed an electrocardiographic review system for displaying ECG data for each of eight patients. Whenever the data for a new patient is to be observed, two trend plots are first displayed on the screen. One of these represents the number of heartbeats per minute and the other represents the number of ectopic beats per minute, the time axis being divided into approximately 240 discrete 1-minute intervals so that the trend data for a 4-hour monitoring period can be displayed. The reviewing physician can move a cursor across the screen to a point of particular interest, for example, to a point along the time axis corresponding to a 1-minute interval during which many ectopic beats were detected. Following this, when a display key in the system is operated, a four-second stationary display of the first ECG waveform of interest which occurred during that 1-minute interval is formed. Thereafter, each operation of the display key controls the display of another 4-second ECG waveform.

Abstract: An improved battery for use with an implantable heart pacer. An implantable heart pacer provides stimulation to the heart of a patient and is normally battery-powered. A primary reason for pacer failure and resulting pacer replacement is failure in the battery or batteries. The present invention provides improved insulation against leakage between positive and negative electrodes of the implanted battery thus extending battery life and pacer life.

Abstract: An electrical circuit for operating upon a slowly varying input signal (on the order of one volt per minute) to provide an output signal representative of the input signal derivative. The circuitry employs at least two feedback loops, one of which is constructed similar to an integrator amplifier. One particularly useful electro-medical application of this apparatus and method lies in the measurement of osmotic fragility of red blood cells, where percentage hemolysis of the blood slowly varies as a function of tonicity of suspension of the medium in which the blood sample is suspended. In this measurement the exact point of maximum slope is important and is provided by the present invention.