JPH07241278A - Electronic sphygmomanometer - Google Patents

Abstract

PURPOSE:To provide an electronic sphygmomanometer capable of calculating an exact blood pressure value. CONSTITUTION:This electronic sphygmomanometer has a pulse wave amplitude correcting means 6 for correcting pulse amplitude in accordance with a relation between a cuff pressure stored in a memory means 3 and a calculated cuff pressure and a pressure value correcting means 7 for likewise correcting the calculated cuff pressure (pressure value) in accordance with the relation between the cuff pressure stored in the memory means 3 and the calculated cuff pressure and has also a blood pressure value determining means 8 for determining the blood pressure value by using the corrected pressure value and pulse wave amplitude.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic sphygmomanometer that corrects a pressure value (cuff pressure) and a pulse wave amplitude and calculates a blood pressure value using the corrected cuff pressure and the pulse wave amplitude.

[0002]

2. Description of the Related Art In an electronic sphygmomanometer, when the pressure in the cuff is converted into an electric signal and a pressure value (cuff pressure) is calculated from this electric signal, as shown in FIG. The actual calculated pressure value has a non-linearity error such as or.

[0003]

In the conventional electronic sphygmomanometer, since the actual calculated pressure value is or, only the calculated pressure value is corrected. However, when the pulse wave component is extracted from the pressure value, the pulse wave component including the non-linearity error is extracted. Therefore, when the pulse wave component has the pressure characteristic as shown in FIG. 6, for example, the pulse wave component is extracted. Then, as compared with the case where the non-linearity error is not included, the pulse wave amplitude on the high voltage side becomes larger than the actual value, and the pulse wave amplitude on the low voltage side becomes smaller than the actual value, as shown in FIG. 7. On the other hand, in the case of having the pressure characteristic as shown in FIG. 6, the pulse wave amplitude is, on the contrary, smaller on the high pressure side and larger on the low pressure side. As described above, when the blood pressure value is calculated based on the pulse wave amplitude including the non-linearity error, there is a problem that an accurate blood pressure value cannot be calculated.

Therefore, the present invention has been made to solve the problems of the prior art, and an object thereof is to provide an electronic sphygmomanometer capable of calculating a more accurate blood pressure value. .

[0005]

In order to achieve the above object, an electronic blood pressure monitor of the present invention comprises a cuff, pressure measuring means for converting the pressure in the cuff into an electric signal, and the electric signal as a pressure value. (Cuff pressure) pressure value converting means, pulse wave extracting means for extracting a pulse wave component from the pressure value, and a relationship between the cuff pressure and the calculated cuff pressure calculated by the pressure value converting means is stored. In accordance with the relationship between the cuff pressure and the calculated cuff pressure previously stored in the storage means, the calculated cuff pressure and the pulse wave amplitude are corrected, and the corrected cuff pressure and the pulse wave amplitude are corrected. It is characterized in that the blood pressure value is calculated by using.

[0006]

In this electronic sphygmomanometer, the calculated cuff pressure and the pulse wave amplitude are corrected based on the relationship between the cuff pressure and the calculated cuff pressure stored in the storage means in advance, and the corrected cuff pressure and the pulse wave amplitude are corrected. Since the blood pressure value is calculated using the pulse wave amplitude after correction, the blood pressure value can be accurately calculated with almost no non-linearity error.

The relationship between the cuff pressure stored in the storage means and the calculated cuff pressure is represented by a function or a numerical table representing the relationship between them or a function or a numerical table representing the relationship between the error and the pressure between the two. It is preferable to correct the calculated cuff pressure and the pulse wave amplitude using this. In particular, in addition to the correction of the calculated cuff pressure, the slope of the relationship between the cuff pressure and the calculated cuff pressure is calculated using the relationship between the cuff pressure stored in the storage unit and the calculated cuff pressure, and the pulse wave is calculated using this calculated value. Conveniently it is provided with pulse wave amplitude correction means for correcting the amplitude.

[0008]

EXAMPLES The electronic blood pressure monitor of the present invention will be described below based on examples. FIG. 1 is a block diagram showing a schematic configuration of an electronic sphygmomanometer according to an embodiment. This electronic blood pressure monitor has a cuff 1
A pressure sensor (pressure measuring means) 2 for detecting the pressure in the cuff 1 and converting it into an electric signal, and a pressure value converting means (not shown) for converting the electric signal into a pressure value (cuff pressure).
And a storage means 3 for storing the relationship between the cuff pressure and the calculated cuff pressure calculated by the pressure value converting means in advance, and a pulse wave component from the pressure value (calculated cuff pressure) calculated by the pressure value converting means. The pulse wave extracting means 4 for extracting, the pulse wave amplitude calculating means 5 for calculating the pulse wave amplitude from the extracted pulse wave component, and the pulse wave based on the relationship between the cuff pressure and the calculated cuff pressure stored in the storage means 3. A pulse wave amplitude correcting means 6 for correcting the wave amplitude, and a pressure value correcting means 7 for correcting the calculated cuff pressure based on the relationship between the cuff pressure and the calculated cuff pressure which are also stored in the storage means 3.
The blood pressure value determining means 8 determines a blood pressure value using the corrected pressure value and the pulse wave amplitude. Of these, the blood pressure value determining means 8 is composed of, for example, an arithmetic processing circuit such as a CPU.

A schematic flow chart of the overall operation of this electronic blood pressure monitor is shown in FIG. When the power is turned on, various data and variables are initialized (ST1), the cuff is pressurized by the pressurizing means (pump, etc.) (ST2), and the cuff pressure reaches the target pressurization value. Whether or not it is determined (ST3), the pressurization is continued until it is reached. After reaching the target pressurization value, a depressurization process is performed to exhaust the cuff at a slow speed (ST4), and in the depressurization process, a blood pressure value (maximum and minimum blood pressure values) is determined (ST5), and finally After determining the value (ST
6) The inside of the cuff is rapidly evacuated (ST7), and blood pressure measurement is completed.

The blood pressure value determination process (ST5) in the flow chart of FIG. 2 is performed as follows. In the block diagram of FIG. 1, the pressure in the cuff 1 is converted into an electric signal by the pressure sensor 2, and the pressure value (cuff pressure) is calculated from the electric signal. The calculated cuff pressure is as described above. Has non-linearity error. However, since the relationship between the cuff pressure and the calculated cuff pressure is stored in the storage means 3 in advance, the pressure value correction means 7 corrects the calculated cuff pressure using this storage relationship.

On the other hand, the pulse wave component is extracted from the electric signal converted by the pressure sensor 2 by the pulse wave extracting means 4, and then the pulse wave amplitude is calculated by the pulse wave amplitude calculating means 5 from one pulse wave component. . The pulse wave amplitude extracted here has a non-linearity error, and the error is proportional to the slope in the relationship between the cuff pressure and the calculated cuff pressure, but as described above, the relationship between the cuff pressure and the calculated cuff pressure is stored in the storage means. The pulse wave amplitude is corrected by the pulse wave amplitude correction means 6 using this memory relationship. Then, the blood pressure value determining means 8 determines the blood pressure value based on the corrected calculated cuff pressure and the pulse wave amplitude.

FIG. 3 is a flowchart showing the correction processing of the pulse wave amplitude by the pulse wave amplitude correction means 6. After starting the blood pressure value determination process (see ST5 in FIG. 2), the cuff pressure signal P _C is captured (S
(T11), the cuff pressure signal P _{C is} digitally filtered to separate the pulse wave signal P _W from the cuff pressure signal P _C (ST12). Since this digital filtering process is not an essential part of the present invention, detailed description will be omitted. From the pulse wave signal P _{W for} one beat, the maximum point P of the pulse wave
_WMAX and minimum point P _WMIN are detected (ST13), pulse wave amplitude W
Is calculated by the following equation (1) (ST14).

W = P _WMAX −P _WMIN (1) Next, the pulse wave amplitude correction value A is obtained (ST15). For this purpose, the relationship between the true pulse wave amplitude W _R and the pulse wave amplitude W calculated in ST14 is defined as W _R = (1 / A) × W (2) Here, the calculated pulse wave amplitude W has a non-linearity error, but the error is proportional to the inclination in the relationship between the cuff pressure and the calculated cuff pressure. For example, if the non-linearity error is 0 as shown in FIG. 6, the slope in the relationship between the cuff pressure and the calculated cuff pressure is always 1. In FIG. 6, the calculated cuff pressure 200
Assuming that the gradient in the relationship between the cuff pressure in mmHg and the calculated cuff pressure is 0.9, the pulse wave amplitude at the calculated cuff pressure of 200 mmHg is about 10% smaller than the true pulse wave amplitude. As for the relationship between the cuff pressure P _C and the calculated cuff pressure P _C ′, assuming that the pressure error E in the case of FIG. 6, as shown in FIG. 4, E = P _C ′ −P _C .. Calculated in (3) and stored in the storage means 3 (see FIG. 1) at fixed pressure intervals, for example, every 16 mmHg. The cuff pressure P _C at the time of calculating the pulse wave amplitude W is between the cuff pressures P _C (N) and P _C (N-1) in which pressure errors are stored as shown in FIG. 5, and P _C (N), P
_C (N-1) of the pressure error is respectively E (N), if E (N-1), the pulse wave amplitude at the cuff pressure range _{[P C (N) -P C (} N-1) ] The correction value A is obtained by the following equation (4) using E (N) and E (N-1).

[0014] However, a _{P C (N) -P C (} N-1) = 16. The corrected pulse wave amplitude W _A is calculated using the pulse wave amplitude correction value A obtained by this equation (4) (ST16). The corrected pulse wave amplitude W _A is obtained by the following formula (2) using the formula: W _A = (1 / A) × W.

Actually, since the slope in the relationship between the cuff pressure and the calculated cuff pressure continuously changes in a curved line as shown by the broken line in FIG. 5, the pulse wave amplitude correction value A also continuously changes. However, when the pulse wave amplitude correction value A is calculated as in equation (4),
The correction value A is calculated so as to change linearly as shown by the solid line in FIG. 5, and the pulse wave amplitude correction value A is one in the cuff pressure range. Therefore, the cuff pressure is P _C (N) or P
_The error becomes larger as it gets closer to _C (N-1). However, this can be solved by reducing the pressure interval when the pressure error E is stored in the storage means 3 in accordance with the magnitude of the pressure error E, that is, by setting the pressure interval smaller than 16 mmHg in the above example.

In the above embodiment, the correction of the pulse wave amplitude is obtained from the relationship between the error between the cuff pressure and the calculated cuff pressure and the pressure. However, a function or a function expressing the relationship between the cuff pressure and the calculated cuff pressure is used. It may be obtained using a numerical table.

[0017]

As described above, the electronic sphygmomanometer of the present invention corrects the calculated cuff pressure and the pulse wave amplitude based on the relationship between the cuff pressure and the calculated cuff pressure stored in the storage means in advance, Since the blood pressure value is calculated using the corrected cuff pressure and pulse wave amplitude, the corrected pulse wave amplitude contains almost no non-linearity error as compared to the conventional case where only the pressure value is corrected. A more accurate blood pressure value can be calculated.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an electronic blood pressure monitor according to an embodiment.

FIG. 2 is a schematic flowchart showing the overall operation of the electronic blood pressure monitor of the same embodiment.

FIG. 3 is a flowchart showing a pulse wave amplitude correction process in a blood pressure value determination process in the flowchart of FIG.

FIG. 4 is a diagram showing a relationship between a cuff pressure and a pressure error stored in a storage means in the electronic blood pressure monitor of the embodiment.

FIG. 5 is a diagram showing an example of calculating a pulse wave amplitude correction value in the electronic blood pressure monitor of the embodiment.

FIG. 6 is a diagram showing a relationship between an actual cuff pressure and a calculated cuff pressure.

FIG. 7 is a diagram comparing a pulse wave amplitude before correction and a pulse wave amplitude after correction.

[Explanation of symbols]

 1 cuff 2 pressure sensor (pressure measuring means) 3 storage means 4 pulse wave extraction means 5 pulse wave amplitude calculation means 6 pulse wave amplitude correction means 7 pressure value correction means 8 blood pressure value determination means

Claims (3)

[Claims] 1. A cuff, pressure measuring means for converting the pressure in the cuff into an electric signal, pressure value converting means for converting the electric signal into a pressure value (cuff pressure), and a pulse wave component from the pressure value. An electronic sphygmomanometer including a pulse wave extracting unit that extracts a pulse wave and a storage unit that stores the relationship between the cuff pressure and the calculated cuff pressure calculated by the pressure value converting unit. Based on the relationship between the pressure and the calculated cuff pressure, the calculated cuff pressure and pulse wave amplitude are corrected,
An electronic blood pressure monitor characterized in that a blood pressure value is calculated using the corrected cuff pressure and pulse wave amplitude. 2. The relationship between the cuff pressure stored in the storage means and the calculated cuff pressure is a function or a numerical table representing the relationship between the two, or a function or a numerical table representing the relationship between the error and the pressure between the two. The electronic sphygmomanometer according to claim 1, characterized in that the calculated cuff pressure and the pulse wave amplitude are corrected using this. 3. A slope in the relationship between the cuff pressure and the calculated cuff pressure is calculated using the relationship between the cuff pressure and the calculated cuff pressure stored in the storage means, and the pulse wave amplitude is corrected using this calculated value. 2. A pulse wave amplitude correcting means is provided.
Electronic blood pressure monitor described.