Sphygmomanometer, blood pressure measurement method, and blood pressure measurement program

A blood pressure measurement method comprising:

• detecting a cuff pressure at a plurality of pulse waves while a cuff is being pressurized;
• for each pulse wave:
• identifying a first minimum time at which the pulse wave is at a minimum value, identifying a second minimum time, later than the first minimum time, at which the pulse wave is next at the minimum value, and identifying a maximum time, between the first minimum time and the second minimum time, at which the pulse wave is at a maximum value;
• calculating a first area of a first waveform between the first minimum time and the maximum time and a second area of a second waveform between the maximum time and the second minimum time, and calculating a first ratio between the first area and the second area;
• calculating a first slope of a first line between the first minimum time and the maximum time and a second slope of a second line between the maximum time and the second minimum time, and calculating a second ratio between an absolute value of the first slope and an absolute value of the second slope;
• calculating a first time length between the first minimum time and the maximum and a second time length between the maximum time and the second minimum time, and calculating a third ratio between the first time length and the second time length;
• identifying the pulse wave at which the first ratio is first ratio is approximately one, as a first pulse wave, identifying the pulse wave at which the second ratio is approximately one, as a second pulse wave, and identifying the pulse wave at which the third ratio is approximately one, as a third pulse wave;
• and
• estimating a systolic blood pressure from the cuff pressure at the first pulse wave, the cuff pressure at the second pulse wave, and the cuff pressure at the third pulse wave.

A non-transitory computer-readable recording medium that records a blood pressure measurement program, wherein the program causes a computer to execute a cuff pressure and pulse wave detecting process comprising:

• detecting a cuff pressure at a plurality of pulse waves while a cuff is being pressurized;
• for each pulse wave:
• identifying a first minimum time at which the pulse wave is at a minimum value, identifying a second minimum time, later than the first minimum time, at which the pulse wave is next at the minimum value, and identifying a maximum time, between the first minimum time and the second minimum time, at which the pulse wave is at a maximum value;
• calculating a first area of a first waveform between the first minimum time and the maximum time and a second area of a second waveform between the maximum time and the second minimum time, and calculating a first ratio between the first area and the second area;
• calculating a first slope of a first line between the first minimum time and the maximum time and a second slope of a second line between the maximum time and the second minimum time, and calculating a second ratio between an absolute value of the first slope and an absolute value of the second slope;
• calculating a first time length between the first minimum time and the maximum and a second time length between the maximum time and the second minimum time, and calculating a third ratio between the first time length and the second time length;
• identifying the pulse wave at which the first ratio is first ratio is approximately one, as a first pulse wave, identifying the pulse wave at which the second ratio is approximately one, as a second pulse wave, and identifying the pulse wave at which the third ratio is approximately one, as a third pulse wave;
• and
• estimating a systolic blood pressure from the cuff pressure at the first pulse wave, the cuff pressure at the second pulse wave, and the cuff pressure at the third pulse wave.