A noninvasive sphygmomanometer capable of obtaining an accurate blood pressure value is provided without complicating a structure and with little time-consuming work. A photointerrupter 31, a wave-shaping circuit 75, a rotation number counting circuit 77, and a discharge amount calculating circuit 78 which measure a discharge amount of a pressure pump 13, and an arm circumference length detecting circuit 79 which calculates an arm circumference length of a subject person based on a relationship between a pressure in a bladder 8 provided in an armband 9 and the measured discharge amount of the pressure pump 13 is provided. Then, a blood pressure value is corrected based on the calculated arm circumference length.
Prior to blood pressure calculations, air is enclosed in a blood pressure measurement bladder to be wound and mounted around the region for measurement, in advance. By referring to the variation in the pressure therein, the circumferential length of the region for measurement is detected based on the variation in the pressure therein during the winding correction determination process for the region for measurement. Then, the process enters blood pressure measurement, and the blood pressure measurement bladder is pressurized or depressurized. The pressure in the blood pressure measurement bladder is detected. A blood pressure based on the detected pressure is calculated according to the circumferential length of the region for measurement which has been detected in advance.
In wrapping a blood pressure measurement cuff enclosing therein a bladder, which is inflated when supplied with air, around a region for measurement, first, a predetermined amount of air is supplied to the bladder and then enclosed therein. Then, the blood pressure measurement cuff is wrapped around the region for measurement of a subject for the purpose of measuring his/her blood pressure. During this wrapping process, relative variations in the pressure in the bladder are sequentially detected. The time period in which the detection results indicate that the variation has not reached a predetermined threshold value, the wrapping proceeds. When the detection results indicate that the variation has reached the predetermined threshold value, the wrapping is terminated.
In blood pressure measurement of a vertebrate through use of an inflatable pressure cuff disposed about a limb of the vertebrate limb and inflated by pump driven by a motor, the air pressure within the cuff is determined at any given time during the inflation of the cuff by calculating the incremental change in pressure in the pressure cuff over a series of small time increments and summing the calculated incremental pressure changes from the initiation of cuff inflation to a desired point in time during the inflation of the pressure cuff. The incremental change in pressure within the cuff is calculated as a function of the incremental change in current drawn by the pump motor over the time increment.
