Abstract: An automatic non-invasive blood pressure monitoring system includes a blood pressure monitor, a blood pressure cuff pneumatically connected to the blood pressure monitor, a deflation valve connected intermediate the blood pressure monitor and the blood pressure cuff, and a controller for automatically controlling the non-invasive blood pressure monitoring.

Abstract: A failsafe supervisor system for a patient monitor which integrates the functions of coordinating the turning on/off of the patient monitor with the user and the system software, alerting the operator in the event the patient monitor turns off due to a power failure, and alerting the operator to improper operation of the patient monitor system's processor hardware or software. Upon detection of such unexpected changes of state or malfunctions during operation of the patient monitor, the patient monitor is powered down in a failsafe manner to a safe state. Additionally, the failsafe supervisor system optionally allows the operator to select a service mode when turning on the monitor, thereby facilitating testing. The entire failsafe supervisor system is preferably implemented in a small one-chip microcontroller so that it can be readily incorporated into the patient monitor's microprocessor control system.

Abstract: A method for selecting fundamental clock frequencies in order to achieve electromagnetic compatibility in electronic products which employ a plurality of clocks. The method require first selecting an ideal frequency for each clock in the product. Then, and until the goal of avoiding coinciding harmonics is complete, the method includes the steps of computing all harmonics of all clock frequencies chosen, determining a minimum difference tolerable in the chosen frequencies and their harmonics for sufficient minimization of electromagnetic interference, and determining if the harmonics of the chosen frequencies coincide impermissibly within the frequency range. If there exists coincidence of harmonics within the predetermined minimum range, then the fundamental frequency of at least one of the clocks corresponding to an interfering harmonic must be adjusted to eliminate the interference.

Abstract: An automated sphygmo-manometer which digitizes the pressure transducer output with sufficient resolution to preserve the details of the measured oscillation complexes. The "composite" arterial pulse signal containing the DC pressure component and the oscillation complexes is processed in a single processing channel so that the amplitudes of the oscillation pulse can be measured in the presence of the static components. Any necessary filtering is performed in the digital domain using known digital signal processing (DSP) techniques. In addition, dither signals may be added to the arterial pulse signal in the single processing channel in order to increase the apparent resolution. A simple finite impulse response (FIR) filter is used to sum respective samples to form high resolution samples from a plurality of low resolution samples.

Abstract: A blood pressure cuff is applied about a subject's artery, and inflated above the systolic level thus fully occluding the artery for a full heart cycle. The cuff pressure is thereafter reduced to permit an increasing flow through the progressively less occluded artery, and a measure of the peak amplitudes of the successively encountered blood pressure (oscillatory complex) pulses stored in memory. Also retained is the cuff pressure obtaining for each stored complex peak. In accordance with varying aspects of the present invention, the stored complex peak-representing data ensemble is corrected for aberrations; and improved data processing operates on the stored (and advantageously corrected) pulse peak data and the corresponding cuff pressure information to determine the subject's systolic arterial blood pressure.

Abstract: The deflation of the inflatable and deflatable cuff worn by a subject during automatic sphygmomanometric measurement is accomplished in unequal size decrements and principally in larger steps than 7 Torr. Each step after detection of the initial oscillations is determined in the first instance by reference to a look-up table or an equation as a function of prevailing cuff pressure. This Base Step dimension is augmented by a factor proportional to the last oscillation amplitude, the factor being increased after detection of the maximum oscillation amplitude. A valve mechanism with at least two different effective orifice sizes is used for deflation, the smaller size effective orifice being used first, to maintain control over the decrement step rate while holding the time for decrement within a predetermined limit of 8 mSec. per Torr, i.e., maintaining the rate above 125 Torr per second.

Abstract: A pulse oximeter is provided including two light emitting diodes. Each LED is energized by a unique modulation signal. Light produced by the LEDs passes through the tissue of a subject and is detected by a photodiode. The photodiode signal is separated by tuned circuits resonant at the two modulation signal frequencies and physiological information signals are recovered from the separated signals by amplitude demodulation. The inventive arrangement provides identification of back-to-back coupled LEDs and narrow band filtering for good noise immunity.

Abstract: A pulse oximetry system is provided in which LEDs of two different wavelengths illuminate tissue containing arterial blood flow. A photodiode receives light from the LEDs and produces electrical signals containing pulsatile components. The components of the two wavelengths are separated and the pulsatile waveforms are monitored until signal peaks are detected at the end of diastole. The waveforms are then integrated over the systolic interval, and the integrals are combined with the signal peak values to determine an index value. The index value is used to select a value representative of oxygen saturation from a look-up table.

Abstract: A blood pressure cuff is applied about a subject's artery, and inflated above the systolic level thus fully occluding the artery for a full heart cycle. The cuff pressure is thereafter reduced to permit an increasing flow through the progressively less occluded artery, and a measure of the peak amplitudes of the successively encountered blood flow (oscillatory complex) pulses stored in memory. Also retained is the cuff pressure obtaining for each stored complex peak. In accordance with varying aspects of the present invention, the stored complex peak-representing data ensemble is corrected for aberrations; and improved data processing operates on the stored (and advantageously corrected) pulse peak data and the corresponding cuff pressure information to determine the subject's mean arterial blood pressure.

Abstract: A blood pressure cuff is applied about a subject's artery, and inflated above the systolic level thus fully occluding the artery for a full heart cycle. The cuff pressure is thereafter reduced to permit an increasing flow through the progressively less occluded artery, and a measure of the peak amplitudes of the successively encountered blood flow (oscillatory complex) pulses stored in memory. Also retained is the cuff pressure obtaining for each stored complex peak. In accordance with varying aspects of the present invention, the stored complex peak-representing data ensemble is corrected for aberrations; and improved data processing operates on the stored (and advantageously corrected) pulse peak data and the corresponding cuff pressure information to determine the subject's diastolic arterial blood pressure.

Abstract: An inflatable, deflatable cuff, worn by the subject, is coupled to an air reservoir which is at a predetermined pressure which is above systolic pressure. The pressure head is established by a pump mechanism preferably located within the reservoir. When the reservoir is operatively coupled to the cuff, the cuff quickly inflates to a desired artery-occluding initial pressure preparatory to a following blood pressure measuring cycle of operation. The air pump resumes air flow into the reservoir when pressure within the reservoir falls below a predetermined threshold in preparation for a subsequent measurement cycle. The pump also supplies air directly to the cuff should the reservoir contents ever be inadequate to inflate fully the occluding cuff.

Abstract: Automated blood pressure monitors utilizing a pressurized cuff are adapted automatically to work with a variety of cuff sizes, including neonatal. An acoustical pressure pulse is generated at the monitor, propagated to and through the cuff, and back to a pressure transducer in the monitor. The total time of propagation is indicative of the cuff size being utilized.

Abstract: An adaptive monitor and method for rapidly determining blood pressure, selects an initial cuff pressure to be applied to an artery of the test subject and then measures the amplitude of pressure pulses caused by the pumping of blood by the subject's heart. The cuff pressure is incrementally increased while the pulse amplitudes are monitored in order to obtain blood pressure readings by the oscillometric method. If the pulse amplitudes decrease for increases in pressure above the initial value, it is taken as an indication that mean arterial pressure is below the initial cuff pressure. Thus the cuff pressure is substantially decreased to a new initial value and the process is restarted.

Abstract: A logarithmic converter circuit comprising an emitter-coupled pair of transistors and a pair of operational amplifiers is provided with a temperature-stabilized environment so that accurate logarithmic conversion is facilitated. One of the pair of transistors is utilized as a temperature sensor to provide a temperature control voltage, which in turn controls the power applied to a heating element disposed adjacent the pair of transistors to maintain a constant semiconductor junction temperature. The heating element may suitably be one or more transistors disposed proximate the pair of transistors on a common substrate. The absolute temperature of the sensor transistor base-to-emitter junction is established by the use of precise gain-setting components, and by adjusting the temperature reference voltage for the correct system gain.