Semiautomatic blood pressure monitor utilizing an electronic sphygmomanometer

A semicontinuous but noninvasive blood pressure monitoring system is described. It consists of a commercial electronic sphygmomanometer which utilizes a microphone under an occluding arm cuff to detect the Korotkoff sounds, a pressure transducer, and a simple gating circuit. The gate passes the cuff pressure signal to a recorder only when a proper Korotkoff sound is detected. The cuff is rapidly inflated to just above the anticipated systolic pressure, then deflated at a steady rate of 2-6 Torr/heartbeat. When diastolic pressure is passed, the cuff is fully deflated momentarily before repeating the cycle. Systolic and diastolic pressures can be recorded up to 3 or 4 times/min. Spurious signals are rejected by the electronics which process the output of the microphone. This allows the use of the system in experiments on exercising man and in environments where unwanted signals exist. The system offers greater versatility than commercial semiautomatic pressure monitors, at less than half the cost.