Abstract: A system for measuring blood oxygen saturation uses a noninvasive optical technique. A patient's arterial blood is illuminated with light at two different wavelengths and the intensity of the reflected light is correlated with an oxygen saturation reference curve to determine the oxygen saturation of the patient's blood. The optical sensor includes one or more controlled heat sources which are used to maintain the patient's tissue at a predetermined temperature. Safety circuits are also provided in order to prevent thermal burns to a patient in the event of a system failure.

Abstract: A method and apparatus for determining a number of important physiologic characteristics of a patient based on a end tidal determinations taken from a single respiratory waveform. In the preferred embodiment, breath detection, end-tidal occurrence, and respiratory information is determined using only the expired CO.sub.2 gas concentration waveform. The system of the present invention is capable of performing the following basic functions: (1) identification of breath-by-breath inspired/expired end-tidal gas concentrations of three or more other expired gases (i.e., O.sub.2, NO.sub.2, and a volatile anesthetic); (2) calculation of the respiratory, inspiratory, and expiratory periods; (3) calculation of the respiratory rate and inspiratory/expiratory ratio; and (4) calculation of the multi-breath and time-trend averages.The preferred embodiment of the invention system comprises a breath detection algorithm which is implemented in two phases--initialization and normal.

Abstract: A method and apparatus for detection of coronary artery disease. The apparatus records and analyzes that portion of the phonocardiogram lying between about 100 to 600 Hz. An electrocardiogram is also recorded and examined in order to pinpoint the diastolic window of PCG data. This window of data is subject to autocorrelation analysis and spectral analysis, resulting in a partial correlation coefficient index and a power density index. A linear combination of these two indices results in a Cardiac Screening Index which is indicative of the presence or absence of coronary artery disease.

Abstract: An improved optical sensor which has increased sensitivity and which is resistant to the effects of ambient light. In one embodiment of the invention, the sensor housing has a flat lower face with a central protrusion in which a plurality of light emitting diodes and an optical sensor are mounted. When the sensor is placed on the patient's tissue, the portion of the sensor face containing the LEDs and detector protrudes slightly into the tissue to provide improved optical coupling of the sensor to the skin. A light absorbing compliant material is attached to the perimeter of the sensor to reduce the effects of ambient light and to provide a cushion to minimize discomfort to the patient. In an alternate embodiment of the sensor, the LEDs and detector are mounted in a horizontal configuration substantially parallel to the surface of the tissue. The light produced by the LEDs is projected into a central chamber of the housing where the respective beams are combined and directed toward the tissue.

Abstract: A noninvasive optical oximeter for measuring oxygen saturation of arterial blood. A sample of blood is illuminated with light at four different wavelengths. Light reflected by the blood is sensed by a photodetector and a plurality of output signals are created in response thereto. The reflected light at each of the four wavelengths is detected after contact with the blood and is correlated with the oxygen saturation of the patient's blood using mathematical relationships for arterial and venous oxygen saturation. The present invention provides a noninvasive backscatter oximeter which is capable of providing accurate indications of a patient's blood oxygen saturation without the need for obtaining prior information relating to the oxygen content of the patient's blood.

Abstract: An improved blood pressure occlusion cuff which is easily attached to the patient's arm and which is comfortable for use over extended periods of time. The preferred embodiment of the invention blood pressure cuff comprises a flexible band, a buckle for releasably securing said band to a person's limb, structure for pressurizing said band to cause it to apply pressure to said limb and for sensing pressure variations related to the flow between said buckle and said limb when said band is secured to said limb.

Abstract: A method for computing optimal hold down pressure for a transducer comprising an array of pressure sensing elements for generation of electrical waveforms indicative of blood pressure in an artery. Using the selected pressure sensing element that is determined to be positioned substantially over the center of the underlying artery, a set of data corresponding to the diastolic pressure and the pulse amplitude pressure is collected and stored. The diastolic pressures and pulse amplitude pressures are taken as a function of hold down pressure over a range of hold down pressures between the pressure at which the artery is unflattened and the pressure at which the artery is occluded. First and second polynomials are fitted to the diastolic pressure data set and the pulse amplitude data set, respectively. The hold-down pressure at the point of minimum slope of the first polynomial fitted to the diastolic versus hold-down pressures values provides one estimate of the correct hold-down pressure.

Abstract: A compact, low noise inflation system for pressurizing occlusion cuffs used in conjunction with automatic blood pressure monitoring equipment. In the preferred embodiment, an electric pump is controlled by a closed-loop, pressure feedback control circuit which compares the cuff pressure with a desired pressurization profile set by the user or stored in a memory device. Acoustic filters are connected to the intake and exhaust ports of the pump to attenuate the intensity of acoustic noise and pressure waves to allow accurate detection of oscillometric pulse data by the blood pressure monitoring system.

Abstract: A system for automatically positioning a blood pressure monitor transducer in a desired position relative to an underlying artery. The positioning system comprises a positioniong motor which drives a gear assembly. The gear assembly is operatively engaged with a lead screw having a follower mounted thereto in threaded engagement therewith. The follower is secured to a strap which is routed through a roller system. As the motor is activated in response to output signals from the sensor mounted within transducer housing, the lead screw will rotate, thereby effectuating lateral movement of the transducer housing and sensor along a path defined by the strap.

Abstract: A cardiovascular monitor having improved safety features and data transmission ability. Sensing devices placed on a patient's body, such as electrocardiogram electrodes and phonocardiogram microphones, are electrically isolated from the data recorder and AC powerline, thereby protecting the patient from dangerously high voltages existing in the recorder and the external power source. Isolation amplifiers are employed in the signal conditioning circuitry at the front end of the recorder. Special isolation transformers are also used to prevent ground loop currents between the signal conditioner and the recorder thus minimizing noise due to powerline leakage. Similarly, isolation amplifiers are used during the playback mode between the recorder and a data processor to avoid ground loop currents between the recorder and the processor.

Abstract: An inflation system for providing rapid, linear inflation of a container, such as an occlusion cuff used in connection with a blood pressure monitoring system. The invention system provides an automatic fast-fill of the cuff to a predetermined pressure level, followed by a smooth, linear pressurization profile which is independent of the volume of the cuff. An efficient electronic actuation system allows the system to inflate the cuff many times using the power supplied by a low power battery. A pressure relief system is provided to automatically terminate operation of the inflation system once systolic pressure has been detected or if the pressure in the system rises above a predetermined level. The system is extremely lightweight and compact, thus allowing a patient to carry the system on his person without undue fatigue.

Abstract: A noninvasive optical oximeter for measuring oxygen saturation of arterial blood. A sample of blood is illuminated with light at two different wavelengths. Light reflected by the blood is sensed by a photodetector and an output signal is created in response thereto. The output signal is processed to form a quotient representing the AC components of the reflected light at each wavelength. The oxygen saturation of the blood is calculated by correlating this quotient with an oxygen saturation reference curve uniquely representative of the blood oxygen saturation characteristics of a particular individual. The reference curve used in the preferred embodiment of the invention is calibrated in a two-step process which minimizes the effects of calibration errors. A first oxygen saturation reference curve is calculated which is based on a linear relationship between the ratio of the AC components of the reflected light.

Abstract: A method for determining the pulse rate of a person. The method of the present invention is implemented in two phases. The first phase involes the determination of pulse intervals and the second phase provides an indication of the pulse rate based on the data produced during the first phase. The first phase is implemented by an algorithm which produces a pulse distribution profile from an array of pulses obtained from an appropriate transducer. In the second phase of the measurement, the distribution is searched to locate the region of maximum density. The pulse rate within the maximally dense region are then averaged to determine pulse rate. The pulse rate detection method of the present invention eliminates a significant number of erroneous pulse signals before calculation of pulse rate, thus providing a more accurate indication of the true pulse rate.

Abstract: An automatic blood pressure monitoring system includes a device which detects the degree of saturation of oxygen in the blood at a peripheral part of the body. The detecting device generates a signal if the degree of saturation is detected to be abnormal. A control device operates a blood pressure measuring device in response to the signal indicating abnormal oxygen saturation. In a second embodiment, a trigger device periodically generates a signal to operate the blood pressure measuring device. When an abnormal oxygen saturation is detected, a signal operates the blood pressure measuring device and the triggering interval is shortened.

Abstract: An electroacoustic transducer having a piezoelectric element disposed on a diaphragm for converting an acoustic signal to an electric signal, and a differential amplifier for amplifying the electric signal. The piezoelectric element is connected between one of two input lines connected to the differential amplifier, and a reference voltage source. A load having substantially the same impedance as the piezoelectric element is connected between the reference voltage source and the other input line. The load may consist of another piezoelectric element.

Abstract: An electronically actuated switching valve for controlling the flow of gas streams in a pneumatic system. The preferred embodiment of the invention comprises a double piloted three-way spool valve which moves within a valve housing having a plurality of ports which cooperate with the spool valve to direct gas streams in a predtermined manner. The position of the valve spool within the housing is controlled by pressure pilots on either side of the valve spool. Electronically actuated solenoid exhaust valves are operable to cause pressure drops in the pressure pilots to cause the valve spool to change position. Once the valve spool has changed position, it is maintained in that position without the need for a continuous supply of electric current to the electronic actuators.

Abstract: An apparatus for effecting automatic repetitive detection of items of living body information, such as blood pressure, heart rate and breathing rate, and for automatically recording the detected living body information in a predetermined two dimensional chart area provided on an anesthesia record sheet, by recording respective indicia representative of the living body information, at respective recording positions in the chart area, which corresponds to times of detection of the living body information, including: (A) a sensing device for detecting the living body information; (B) a recording device having a support for supporting the record sheet so as to permit manual recording of auxiliary information other than the living body information on the record sheet, and further having a recording member(s) movable relative to the record sheet for recording the indicia in the chart area; and (C) a control device, responsive to the sensing device, for determining the recording positions of the indicia based on the

Abstract: A noninvasive optical oximeter for measuring oxygen saturation of arterial blood. A sample of blood is illuminated with light at two different wavelengths. Light reflected by the blood is sensed by a photodetector and an output signal is created in response thereto. The output signal is processed to form a quotient representing the AC components of the reflected light at each wavelength. The oxygen saturation of the blood is calculated by correlating this quotient with an oxygen saturation reference curve uniquely representative of the blood oxygen saturation characteristics of a particular individual.

Abstract: A method and apparatus for efficiently coupling a transceiver to an AC power line transmission system. The preferred embodiment of the coupling system comprises a line coupling network and first and second filter ports. The first filter port is connected to a resonant circuit having bandpass filtering characteristics adapted to the specific needs of the transmitter portion of the transceiver. The second filter port is isolated from the low impedance of the AC power line and is connected to a high quality factor filter having bandpass filtering characteristics adapted to the specific needs of the receiver portion of the transceiver.

Abstract: A blood pressure monitoring system is disclosed for monitoring blood pressure during stress testing or other physical activity as well as when quiescent. The blood pressure monitoring system of the present invention includes an inflatable cuff utilized in conjunction with a controllable electric air pump and deflation valve. Audio transducers are utilized to detect pulse sound at the proximal and distal edges of the inflatable cuff and pulse sound amplitudes as well as the time delay between pulse sounds proximal to the cuff and distal to the cuff are determined. Pulse sound amplitudes are then multiplied by time delay values for selected cuff pressures to generate a greatly enhanced blood pressure evaluation curve. In a preferred mode of the present invention digital filters and statistical analysis are then employed to determine systolic and diastolic blood pressure from the evaluation curve.