TECHNICAL FIELD

The present invention relates to a blood pressure measuring apparatus configured to measure blood pressure of a subject by use of a cuff.

BACKGROUND ART

In this kind of blood pressure measurement, cuffs having different volumes are used in accordance with categories of subjects including adults, children and neonates. Internal pressure of a cuff suitable for measurement of blood pressure differs from one category of subjects to another. Generally, the value of the internal pressure suitable for a child cuff is higher than the value of the internal pressure suitable for a neonate cuff, and the value of the internal pressure suitable for an adult cuff is higher than the value of the internal pressure suitable for the child cuff. Therefore, it is necessary to avoid a situation that the internal pressure of the neonate cuff is set at the value suitable for the adult cuff.

In consideration of the aforementioned situation, target values of the internal pressures of the cuffs are set correspondingly to the categories of the subjects or the cuff types. For example, the maximum value of the internal pressure of the neonate cuff for newborn babies is set at 150 mmHg (see Non-Patent Literature 1). In an apparatus described in Patent Literature 1, control is performed to stop or suppress pressurizing operation so as to prevent the internal pressure of the cuff from exceeding the target value, while monitoring the internal pressure of the cuff.

CITATION LIST

Patent Literature

[PTL1] U.S. Pat. No. 4,969,466

Non-Patent Literature

[NPL1] IEC 80601-2-130 (particularly see 201.12.1.104)

SUMMARY OF INVENTION

Technical Problem

Even when the pressurizing operation performed by a pressurizing mechanism such as a pump is stopped or suppressed, the internal pressure of the cuff does not immediately stop increasing due to inertia of the mechanism or air. Therefore, it is necessary to predict a timing at which the internal pressure of the cuff will reach the target value and to stop or suppress the pressurizing operation prior to the predicted timing. For example, when the increase rate of the internal pressure of the cuff is measured in real time during a pressurizing process, the timing at which the internal pressure of the cuff will reach the target value can be predicted based on the measured value.

In order to establish such prediction, temporal change (pressurizing rate) of the internal pressure of the cuff during the pressurizing process has to be linear. However, there is a case in which the change is non-linear. In such a case, it is difficult to predict the timing at which the internal pressure of the cuff will reach the target value. When the pressurizing operation is stopped or suppressed prior to a proper timing, blood pressure of a subject whose systolic blood pressure is relatively high may not be able to be measured properly. When the pressurizing operation is stopped or suppressed later than the proper timing, there may occur a problem of excessive pressurization.

An object of one aspect of the invention is to provide a blood pressure measuring apparatus wherein accuracy of pressurization control of internal pressure of a cuff is improved.

Solution to Problem

According to one aspect of the invention, there is provided a blood pressure measuring apparatus configured to measure blood pressure of a subject by use of a cuff, comprising:

a connecting section to which a tube communicating with the cuff is connected;

an air way communicating with the connecting section;

a pressurizing/depressurizing section configured to perform at least one of air feeding to the cuff by way of the air way and air discharging by way of the air way to thereby increase or decrease an internal pressure of the cuff;

a first controlling section configured to cause the pressurizing/depressurizing section to initiate the air feeding while performing the air discharging to thereby cause the internal pressure to transit from a pressure transient state to a pressure steady state or from the pressure steady state to the pressure transient state;
a determining section configured to determine whether the internal pressure has transited to the pressure steady state by way of the pressure transient state; and
a second controlling section configured to cause the pressurizing/depressurizing section to suppress or stop the air discharging while continuing the air feeding, in accordance with determination made by the determining section.

With the above configuration, the first controlling section controls the operation of the pressurizing/depressurizing section so that the pressure inside the flow path including the air way and the tube can be constant prior to the pressurizing operation performed by the second controlling section. Thus, the timing at which the internal pressure of the cuff will reach the target value can be easily predicted so that the pressurizing operation can be stopped or suppressed at a proper timing. Accordingly, it is possible to provide a blood pressure measuring apparatus wherein accuracy of pressurization control of the internal pressure of the cuff is improved.

