1460413 Measuring systolic and diastolic pressure AMBITEX CORP and CENDEV CORP [trading as AMBITEX CO] 12 Feb 1975 [19 Feb 1974] 5934/75 Heading G1N In an apparatus for measuring a patients' systolic and diastolic blood pressure two independent measurements of the patient's heart beat are taken using a pressure transducer 18 which measures the pressure inside a cuff 12, and a microphone 24 which senses the noises from the constricted blood flow downstream of the cuff. These signals are processed and supplied to a coincidence circuit 21. The pressure at the start and at the termination of the signal from the coincidence circuit 21 is measured (after the cuff 12 has been pumped up to stop the blood flow and while the pressure is allowed to decrease slowly). These two measurements correspond to the systolic and the diastolic pressure. The invention makes use of the pronounced acoustic pulses (Korotkoff sounds) that can be detected as the pressure in the cuff is slowly decreased. The sounds start when the systolic pressure is reached and die away at diastolic pressure. The pressure is supplied from a source 15 via a valve 14 that is controlled by a logic circuit 31, which also controls a valve 17 that allows the pressure to decrease. Initially the pressure is increased at a given rate for a set range, held for a given interval, and then the procedure is repeated. This is continued till no signals are detected by the transducers during two sucessive time intervals. Then the pressure is allowed to decrease slowly. The pressure transducer output is differentiated to provide a signal representing the heart beat. This signal is fed via a filter 20 and a threshold circuit B to the coincidence circuit 21. The coincidence circuit also receives the signal from the microphone which is connected via an acoustical conduit 22 to a small cup secured to the patient's arm as shown. The microphone's output signals is passed via a further filter 26 and a threshold circuit. The pressure transducer's signal is also fed via an A-D converter which supplies a display device that records and displays the pressure at the beginning of the pulses coming from the coincidence circuit 21 and at the finish of the pulses coming from the coincidence circuit 21.
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