| 摘要 |
<p>PURPOSE:To achieve a higher measuring accuracy of a minimum blood pressure value and a higher reliability by extracting a flat portion of a pulse wave from a pulse waveform detected to determine a pressure cuff and bag as minimum blood pressure value as obtained when the flat portion of the pulse wave vanishes. CONSTITUTION:A phototransistor 1b receives reflected light of infrared rays projected to a blood tube with a pressure cuff and bag 1 with an infrared LED 1a and outputs a reflected light signal (a pulse wave signal Pw) to an MPU 6 through an amplifier 9 and an A/D converter 8. The MPU 16 applies a differentiation processing to the signal Pw(i) of a pulse wave transistor 1 so that the pulse wave signal thus differentiated corresponds to a flat portion of a pulse wave when the signal is near 'zero level' at the rising thereof. Time t is determined to be in a section where the Pw(i) is at two threshold levels predetermined (negative side Th- and positive side Th+) and is measured. Then, when the time t falls below a specified tS, the flat portion of the pulse wave is considered as vanishing and a pressure cuff and bag in this point is determined to be the minimum blood pressure value PDIA.</p> |
