A fully automatic portable blood pressure recorder.

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Abstract
A fully automatic portable device, weighing 4 3/4 lb., has been developed to record systolic and diastolic pressures and heart rates in subjects at work and home, while driving, and during sleep at home. A timer activates a magnetic valve releasing N2 to inflate a conventional cuff and to move a spring-loaded piston which controls the electronic circuitry and gas flow and records the pressure in the system at 10-mm steps from 240 to 20 mm Hg. These pressure signals and the Korotkoff sounds from a crystal microphone are modulated onto tape as frequencies which are later demodulated to voltages which drive a conventional direct-current penwriter. Sixty recordings are possible before the N2 tank needs recharging. Recordings can be programmed at intervals of 1-60 min. The calibration scale has proved accurate and the recorded blood pressures agree with 2-4% with simultaneously recorded auscultatory values. The device is unique in that the subject is totally uninvoled and a blood pressure scale is recorded with each pressure determination.