JPS5834159B2 - Pressure correction method in electronic blood pressure monitor - Google Patents

Description

[Detailed Description of the Invention] This invention provides the following steps for the operation or operation of a pressure correction type electronic blood pressure monitor: power on → pressurization →
Measurement → Exhaust → Pressure → Measurement → Exhaust (repeat from then on).

In electronic blood pressure monitors that use semiconductor pressure sensors, the temperature drift of the semiconductor pressure sensor is large, so the pressure immediately after the power is turned on to start measurement is considered to be atmospheric pressure, and this pressure is stored as a correction value. The value obtained by subtracting the above correction value from the output is displayed as the pressure measurement value.

However, if the correction value is set to 11 (uncorrected) and the button is pressed when the device is used for a long period of time due to repeated measurements or left in the power-on state, errors due to drift become noticeable.

Therefore, an error occurs in the measured value, making it impossible to expect accurate measurement.Also, if the measured value is equipped with an exhaust valve that automatically closes when the measured value reaches atmospheric pressure, the measured value will not always be the above-mentioned corrected value. If so, the exhaust valve will not close and measurement will be impossible.

Countermeasures against the negative drift in which the correction value decreases are relatively easy and have already been devised, but no adequate countermeasures have been taken against the positive drift.

The present invention has been made in view of the above-mentioned circumstances, and provides a pressure correction method for an electronic blood pressure monitor that can correct the positive drift that causes the measured value to show a higher value.

This invention is based on the fact that temperature drift does not occur in a short period of time on the order of seconds, but becomes more noticeable when the button is used for a relatively long period of time; We are focusing on returning the atmosphere to its original size.

Then, if the pressure close to atmospheric pressure continues for a long time, it is determined that this is the result of an error caused by temperature drift, and the error caused by temperature drift is automatically corrected.

That is, in this invention, the pressure sensor output in a state open to the atmosphere is used as a correction value, a value slightly larger than this correction value is used as a set value, and a state in which the pressure sensor output is between the set value and the correction value is achieved. The present invention is characterized by a pressure correction method that is pressed on the electronic sphygmomanometer so that a value obtained by adding a required value to the above correction value is stored as a new correction value when the pressure continues for a required period of time.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Now, referring to FIG. 1, the electronic blood pressure monitor includes a blood pressure monitor main body 20 with a built-in blood pressure measurement circuit, a cuff 21 button connected to this main body 20 and containing a rubber bag for ischemia, and a rubber bulb 22 for adding pressure to an exhaust valve. and a microphone for collecting Korotkoff sounds (path shown).

The cuff 21 and the rubber bulb 22 are connected by a rubber tube 27, and one end of the rubber tube 27 is connected to a plug 29 provided on the main body 20.

In addition to the blood pressure monitor body 20, the pressure inside the arm body 21 transmitted from the plug 29 through the rubber tube 28 is transmitted to the semiconductor pressure sensor 2.
Detected by 3.

The output of the pressure sensor 23 is AD converted by an AD converter 24.

In this embodiment, the blood pressure measurement process is carried out by the microprocessor 2.
It is executed in 5.

Microprocessor 25 takes in pressure information from AD converter 24 and Korotkoff sound and pulse sound information from the microphone to determine blood pressure measurements.

This blood pressure measurement value is then displayed on the display 26.

In such an electronic blood pressure monitor, when starting measurement, the rubber tube 27 is separated from the plug 29, and the power is turned on.

After a certain period of time has elapsed, the pressure sensor 23
Since the correction value has been taken in from the rubber tube 27, the rubber tube 27 is connected to the plug 29, and blood pressure measurement becomes possible.

Blood pressure measurement by the microprocessor 25 is performed according to the procedure shown in FIG.

FIG. 2 mainly shows the pressure measurement procedure, and the pressure sensor 23 is corrected during this pressure measurement process.

-j, take in the output value of the pressure sensor 23 and proceed to step 1.
, Step 2 stores this captured value in the memory as correction values P1 and 1-.
This is the value when the plug 29 is removed and the pressure sensor 23 is exposed to the atmosphere.

Therefore, the correction value P1 indicates atmospheric pressure, and this value P1 serves as a reference for blood pressure measurement.

The microprocessor 25 is equipped with a timer (shown in the diagram) for measuring whether pressure very close to atmospheric pressure continues for a certain period of time or more in order to detect errors due to drift.

After storing the correction value P1, this timer is cleared and the timekeeping operation is restarted in step 3, and a suitable small set value α is added to the correction value P1, and the addition result is stored as P2 in step 4. The set value α is, for example, a pressure of 1 mm.
The value corresponds to Hg.

Then, the output value is read from the pressure sensor 23, step 5, and step 6 is checked to see if this pressure measurement value exceeds the above addition result P2.If the measurement value exceeds P2, addition for blood pressure measurement is performed. The timer is cleared as it is in the pressure stage, and in step 7, the correction value P1 is calculated from the measured value.
The result of subtracting is taken as the pressure P at that time, and step 8 moves on to blood pressure measurement processing.Step 9゜Blood pressure measurement processing is, as is well known, after increasing the pressure inside the cuff 21 to a predetermined pressure 1, As the pressure is gradually evacuated and reduced, the pressure P at the time when Korotkoff sounds begin to be detected and the pressure P at the time when Korotkoff sounds are no longer detected are defined as the systolic blood pressure and the diastolic blood pressure, respectively.

In step 9, blood pressure measurement processing is performed at each point in time, and the process returns to step 5. Blood pressure measurement is carried out by repeating the processing in steps 5 to 9 at predetermined time intervals.

If the measured value is smaller than P2 in step 6, the process moves to step 10, where the measured value and correction value P1 are compared.

If the measured value is equal to the correction value P1, there is no error due to drift, and the process proceeds to step 7.

In this case, the pressure sensor 23 is only open to the atmosphere and pressurization for blood pressure measurement has not started.

Here, only positive drift is considered and negative drift is not considered, so if the answer in step 10 is NO, the measured value exceeds Pl and is less than P2.

In this case, the process advances to step 11 to check whether the set time of the timer has elapsed.

That is, in step 11, it is checked whether the measured value exceeds Pl and is below P2 for a certain period of time (for example, 10 seconds) or more.

If the drift disappears, the measured value becomes Pl before the timer set time elapses.

If the timer setting time has elapsed while the measured value exceeds Pl and is below P2, it is assumed that an error has occurred due to drift, and the process proceeds to step 12, where P2 is set as a new correction value and Pl is set.
Store it in memory instead.

Then, return to step 3.

In the above example, the set value α was set to a value corresponding to 1 rrrm Hg, but the set value α can be determined as appropriate depending on the degree of drift of the pressure sensor 23.

The drift of the pressure sensor 23 during blood pressure measurement is 1 wa K.
An example is shown in FIG. 3 in which the correction value is corrected by increasing the correction value by a value corresponding to 1rrrm Hg, assuming that the value is equal to or greater than the value corresponding to 1rrrm Hg.

Here, the set value α is 2 rran Hg or more, for example 3
It is set to a value equivalent to mm Hg.

If YES in step 11, a value corresponding to 1wnHg is added to the correction value P1 in step 13.

This allows the correction value P1 to be corrected in small increments, and therefore the display contents can also be changed in stages.

Further, in the above example, the drift of the pressure sensor 23 is corrected by the microprocessor 25, but it can also be corrected by a combination of logic circuits.

That is, a value P2 that is slightly larger (by α) than the correction value P1 is set as a set value, and this set value P2 and the pressure sensor 23
A first comparator generates an output when the output of the pressure sensor 23 is a dog, and a first comparator generates an output when the correction value P1 and the output of the pressure sensor 23 are equal. It consists of a second comparator and a delay circuit (! or timer) that is reset and restarted by the OR output of the outputs of both comparators, and the set value of the first comparator is determined by the output of the delay circuit. P2 may be stored as a new correction value, and the delay circuit may be reset and restarted.

A new correction value may be created by adding a required unit value (smaller than α) to the correction value P1 based on the output of the delay circuit, and the delay circuit may be reset and restarted.

As described in detail above, according to the present invention, it is possible to constantly correct errors due to positive drift that is inevitable in semiconductor pressure sensors, so accurate measurements can be expected even if the electronic blood pressure monitor is used for a long time.

Further, the characteristics of the semiconductor pressure sensor, which are small, lightweight, easy to remove, and highly accurate, can be fully utilized.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an electronic blood pressure monitor, FIG. 2 is a flow chart showing a pressure correction procedure using a microprocessor, and FIG. 3 is a flow chart showing a modification of the above procedure. 23... Semiconductor pressure sensor, 25... Microprocessor.

Claims (1)

[Claims] 1. An electronic blood pressure monitor that stores the pressure sensor output in a state open to the atmosphere as a correction value and presses a button to subtract the correction value from the pressure sensor output when blood pressure is measured to correct the pressure sensor output. The first step is to set a value slightly larger than the above correction value as the set value and compare this set value with the pressure sensor output.
a second comparison means for comparing the correction value and the pressure sensor output, and a clocking means for counting the hexagram and the required time, and the pressure sensor output is at a value between the set value and the correction value. A pressure correction method for an electronic blood pressure monitor that stores a value obtained by adding a required value to the above correction value as a new correction value when a certain condition continues for more than the above required time. 2. A pressure correction method for an electronic blood pressure monitor according to claim 1, characterized in that the set value is used as a new correction value.