Patent ID: 6582374
Filing Date: 2003-06-24
Classification: A61B

Abstract:
An apparatus for automatically measuring a blood pressure of a living subject, comprising:an inflatable cuff which is adapted to be wound around a portion of the subject, where a cuff pulse wave including a plurality of heartbeat-synchronous pulses occurs to the cuff when a pressure in the cuff is changed; a heartbeat-synchronous-wave detecting device which detects, from the subject, a heartbeat-synchronous wave including a plurality of heartbeat-synchronous pulses; a pulse-period determining means for iteratively determining a pulse period of the subject based on a time interval between respective prescribed periodic points of each pair of successive heartbeat-synchronous pulses of the heartbeat-synchronous wave detected by the heartbeat-synchronous-wave detecting device during the changing of the pressure of the cuff; an estimated-pulse-pressure determining means for iteratively determining, for each of the pulse periods iteratively determined by the pulse-period determining means, an estimated pulse pressure of the subject during the changing of the pressure of the cuff, based on each pair of successive pulse periods of the pulse periods, according to a predetermined relationship between pulse pressure and a pair of successive pulse periods; a correction-factor determining means for iteratively determining, for each of the estimated pulse pressures iteratively determined by the estimated pulse pressure determining means, a correction factor to correct said each estimated pulse pressure, to a predetermined value; a corrected-cuff-pulse-wave-amplitude determining means for iteratively multiplying, by the correction factor determined by the correction-factor determining means for said each of the estimated pulse pressures, an amplitude of one of the heartbeat-synchronous pulses of the cuff pulse wave that corresponds to said each of the estimated pulse pressures, and thereby iteratively determining a corrected amplitude of said one heartbeat-synchronous pulse of the cuff pulse wave; an estimated-blood-pressure determining means for iteratively determining an estimated blood pressure of the subject during the changing of the pressure of the cuff, based on said each of the pulse periods iteratively determined by the pulse-period determining means, according to a predetermined relationship between estimated blood pressure and pulse period; a blood-pressure-correction-value determining means for iteratively determining, for said each of the pulse periods, a blood-pressure correction value to correct a corresponding one of the estimated blood pressures iteratively determined by the estimated-blood-pressure determining means, to a predetermined value; a corrected-cuff-pressure determining means for subtracting, from a pressure of the cuff at a time of detection of one of the heartbeat-synchronous pulses of the cuff pulse wave that corresponds to said each of the pulse periods, the blood-pressure correction value determined by the blood-pressure-correction-value determining means for said each of the pulse periods, and thereby determining a corrected pressure of the cuff for said each of the pulse periods; and a blood-pressure determining means for determining a blood pressure of the subject based on a change of the respective corrected amplitudes of the respective heartbeat-synchronous pulses of the cuff pulse wave determined by the corrected-cuff-pulse-wave-amplitude determining means, with respect to the respective corrected pressures of the cuff determined by the corrected-cuff-pressure determining means for the respective pulse periods.