AMBULATORY INSTRUMENT FOR MONITORING INDIRECT BEAT-TO-BEAT BLOOD-PRESSURE IN SUPERFICIAL TEMPORAL ARTERY USING VOLUME-COMPENSATION METHOD

A portable instrument, based on a volume-compensation technique, is de signed for ambulatory monitoring of indirect beat-to-beat blood pressu re (BP) in the superficial temporal artery. The instrument consists of a small disc-type cuff and a portable unit carried by the subject. Se veral components are integrated in the cuff for applying counter-press ure to the artery, i.e. a reflectance-type photo-plethysmographic sens or for arterial volume detection, a pressure sensor for cuff pressure P-c measurement and a nozzle flapper-type electro-pneumatic convertor for controlling P-c. The portable unit includes volume servo control c ircuitry and a microprocessor-based signal-processing and recording un it. This automatically performs all the necessary measurement procedur es and stores into a memory le element the processed systolic, mean an d diastolic blood pressure data, together with pulse intervals on a be at-to-beat basis from the servo-controlled P-c (indirectly measured BP waveform). With this instrument, momentary changes in BP during ambul atory situations such as bicycle ergometer exercise and daily activiti es including motorway driving are successfully recorded. From the resu lts of simultaneous measurement of the subject's posture changes, the effect of posture change on blood pressure, e.g. baroreceptor-cardiac reflex, is also clearly demonstrated.