Patent ID: 8734354

Claim:
A sphygmomanometer, that measures blood pressure in accordance with an oscillation in an artery wall, resulting from an arterial pulse correspondent with a change in cuff pressure, comprising: a cuff that is connected to a sphygmomanometer main body by a tube; an air supply unit for supplying air to and pressurizing the cuff, the air supply unit being detachable from the sphygmomanometer main body, and forming a single unit when attached to the sphygmomanometer main body; a mode switch for selecting a measurement mode from among a Normal mode that measures blood pressure automatically, a Slow mode that measures blood pressure automatically, and a Stethoscope mode for measuring blood pressure manually via a stethoscope; a control unit for controlling opening and closing of an electromagnetic valve of the sphygmomanometer to adjust a speed at which air is exhausted from the cuff according to the measurement mode selected via the mode switch so that the control unit controls the electromagnetic valve to: i) keep the exhaust speed at a first preset exhaust speed during blood pressure measurement when the Normal mode is selected by the mode switch; ii) keep the exhaust speed at a second preset exhaust speed during blood pressure measurement when the Slow mode is selected by the mode switch, the second preset exhaust speed being approximately half of the first preset exhaust speed; and iii) keep the exhaust speed at a third preset exhaust speed during blood pressure measurement when the Stethoscope mode is selected by the mode switch, the third preset exhaust speed being approximately the same as the second preset exhaust speed; a display unit which displays a blood pressure measurement result and the selected measurement mode; a memory storing pressure values measured by the pressure sensor during depressurization of the cuff; wherein the control unit determines a systolic blood pressure based on the stored pressure values; the control unit obtains a pressure value as a first candidate from the stored pressure values at a point where a difference between a squared value of a measured amplitude of the pressure and a squared value of an estimated amplitude of the pressure is within a first prescribed percent range of a maximum amplitude of the pressure for a first time, the estimated amplitude being estimated from temporally previous pressure values; the control unit obtains a pressure value as a second candidate from the stored pressure values at a point where a difference between the squared values is within a second prescribed percent range of the maximum amplitude for a first time as seen from a timing of the maximum amplitude, and the control unit determines a blood pressure corresponding to the first candidate as the systolic blood pressure when a difference between the first candidate and the second candidate is within a prescribed value.