Biological information measurement apparatus and biological information measurement method

A biological information measurement apparatus comprising:

• a pressure sensor which includes a pressure detector;
• a pressing mechanism which is placed adjacent to the pressure sensor and configured to press the pressure sensor against an artery in a living body;
• a press controller which is configured to control a pressing force to be exerted by the pressing mechanism;
• a blood flow sensor which is placed adjacent to the pressure sensor, and which is used for measuring blood flow information indicating a flow of blood that flows through the artery;
• a signal processor which is configured to measure the blood flow information based on an output signal of the blood flow sensor;
• a processor which is configured to decide a first pressing force to be exerted by the pressing mechanism based on:
• the blood flow information that is measured by the signal processor during a pressing force control time period when the pressing force is either increased or decreased by a control of the press controller;
• and
• information of a pressure pulse wave that is a blood pressure wave, and is detected by the pressure detector during the pressing force control time period;
• and
• a record controller which, on a recording medium, is configured to record the pressure pulse wave that is detected by the pressure detector in a first state where the pressing force to be exerted by the pressing mechanism is controlled to the first pressing force by the press controller, and the blood flow information that is measured by the signal processor in the first state,
• wherein the blood flow information is a blood flow velocity,
• wherein the processor is configured to:
• determine a first time period in which a change rate of the information of the pressure pulse wave detected during the pressing force control time period is equal to or smaller than a threshold;
• determine a second time period which is within a part of the first time period and which is a continuous time period in which the blood flow information is within a predetermined range while setting a timing when the pressing force is controlled to be minimum, as a starting point of the second time period;
• decide one of pressing forces in the second time period, in which the blood flow velocity is within the predetermined range, to prevent variation of the blood flow velocity being increased, as the first pressing force;
• and
• select a time period which extends from the starting point of the second time period, to a timing when the pressure pulse wave having a maximum amplitude is detected in the first time period, as the part of the first time period,
• wherein the blood flow sensor is configured to non-invasively measure the blood flow velocity by an ultrasonic Doppler method or laser Doppler method, and
• wherein the pressure detector is configured with a plurality of rows of elements, which are arranged in a horizontal direction perpendicular to a blood flow direction in the artery.