JPH03231631A - Electronic blood pressure gauge - Google Patents

Abstract

PURPOSE:To enable the determining of a correct minimum blood pressure even when a time- series change in amplitude of a pulse wave of a person to be measured is disturbed by arranging a fist minimum blood pressure determining means for calculating an temporary minimum blood pressure and a second minimum blood pressure determining means to calculate the amplitude of the pulse wave. CONSTITUTION:In a pressure reducing process, a first minimum blood pressure determining means which calculates an amplitude of a pulse wave by an artery beating of a cuff pressure in a pressure reducing process and a temporary minimum blood pressure P(d) by an expression of P(d)={3XP(M)-P(S)}/2 from a max. blood pressure P(S) and an average blood pressure P(M) as measured in a pressure changing process and a second minimum blood pressure determining means which determines a comparison pulse wave amplitude H(D) by an expression of H(D)=H(M)XK from a pulse wave amplitude H(M) at an average blood pressure P(M) and a minimum blood pressure determining coefficient K. Then, a cuff pressure P(i) as given when the cuff pressure P(i) in the pressure changing process is below the temporary minimum blood pressure P(d) as calculated by the first minimum blood pressure determining means while the pulse wave amplitude H(i) falls below the comparison pulse wave amplitude H(D) as calculated by the second minimum blood pressure determining means is determined to be the minimum blood pressure P(D).

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a blood pressure monitor that employs a vibration method for measuring blood pressure values from pulse wave amplitude.

[Conventional technology]

Generally, in an electronic blood pressure monitor, as shown in FIG. 2, a cuff 32 is wrapped around a blood pressure measurement site 31 (for example, the upper arm), and the pressure of the cuff 32 is increased above the systolic blood pressure to occlude the artery. after that,
When the pressure is reduced at a slow rate, oscillations (pulse waves) in the cuff pressure occur in response to the arterial pulsation. FIG. 4 is a graph showing changes in cuff pressure during a slow decompression process. FIG. 5 is a graph showing vibration components extracted and separated from the cuff pressure signal of FIG. 4.

Hereinafter, the height of the vibration component (pressure difference) will be referred to as pulse wave amplitude. The transition process of pulse wave amplitude will be explained with reference to FIG. During the decompression process, the pulse wave amplitude is small (section C).
, then gradually increases (section B), reaches the maximum pulse wave amplitude at time 9), and then gradually decreases again (section C). At this time, in the cuff pressure decreasing process, the cuff pressure at which the amplitude begins to increase corresponds to the systolic blood pressure P (S) at time 3).
, the point where the pulse wave amplitude is maximum corresponds to the mean blood pressure P, (M) at time 9), and the principle of determining blood pressure from this pulse wave amplitude is known as the vibration method or oscillometric method.
Often used in electronic blood pressure monitors.

As a method for determining the diastolic blood pressure of an electronic sphygmomanometer based on the vibration method, first, the rate of decrease in pulse wave amplitude after the maximum pulse wave amplitude is shown, that is, the pulse wave amplitude H(i) and one beat before. A method in which the ratio of the pulse wave amplitude H(i-1) is calculated using the relational expression, H(i}/H(i-1), and the cuff pressure at which the rate of decrease is small is set as the diastolic blood pressure (hereinafter referred to as the actual measurement method). ), secondly, the systolic blood pressure P
(S) and mean blood pressure P (M), diastolic blood pressure P (D
) as the relational expression, P (D) = (3P (M) −P (S) }/
2 estimation method (hereinafter referred to as estimation calculation method), 3rd method
Then, the pulse wave amplitude H (M) at the time of mean blood pressure P (M) is multiplied by the diastolic blood pressure determination coefficient K, and the product is compared with the pulse wave amplitude in the depressurization process that has passed the mean blood pressure P (M). Conventionally, a method (hereinafter referred to as pulse wave amplitude comparison method) of determining the diastolic blood pressure based on the pulse wave amplitude has been used.

[Problem to be solved by the invention]

In the conventional method for determining diastolic blood pressure using an electronic sphygmomanometer, the first problem is when the time-series change in the pulse wave is not clear (Fig. 6,
(Fig. 7), and secondly, when the time-series change in pulse wave amplitude is disturbed by body movements (artifacts) of the person being measured during measurement, individual differences in the measurement site of the person being measured, electrical noise, etc. This causes an error in the diastolic blood pressure value. The present invention aims to solve the problem caused by the second cause, and will be explained using a pulse wave amplitude comparison method and an estimation calculation method as examples. FIG. 9 is an example of an incorrect determination of diastolic blood pressure using the pulse wave amplitude comparison method. In the decompression process, the pulse wave amplitude begins to increase from time 3.

The cuff pressure at time 9, which indicates the maximum pulse wave amplitude, corresponds to the mean blood pressure P (M), and the pulse wave amplitude at that time is expressed as H (9).
shall be. During the decompression process, the pulse wave amplitude usually decreases as shown in Figure 5. However, due to the above-mentioned body movements and other causes, the pulse wave amplitude may differ from the regular decrease in the regular decrease process of the pulse wave amplitude. If a small peak of (
There is a time 11). In the regular pulse wave amplitude decreasing process, the pulse wave amplitude at time 11 shows H'(11), and H(13) shows the pulse wave amplitude after multiplying H(9) and the diastolic blood pressure determination coefficient.
) should be the diastolic blood pressure, but as in the example in Figure 9, if the pulse wave amplitude at time 11 is H, (11), then H (9) and the diastolic blood pressure determination coefficient The product of Ni is H(11
), so H(13
) to determine a different diastolic blood pressure value. Further, FIG. 10 shows an example in which the same erroneous determination of the diastolic blood pressure as described above occurs using the estimation calculation method. During the pressure reduction process, the pulse wave amplitude begins to increase at time 3 in FIG. During the pressure reduction process, the pulse wave amplitude usually increases and reaches its maximum at time 9, as shown in FIG. Due to causes such as body movement, the pulse wave amplitude may be small as shown at time 8 in FIG. 10 during the regular process of increasing the pulse wave amplitude. Originally, the diastolic blood pressure P (D) was calculated by the relational expression, P (D) = ( 3XP (9)-P (3)}/2, but in this case, in the estimation calculation method,
The pulse wave amplitude H(7) at time 7 is the maximum amplitude, and from the cuff pressure P(7) and systolic blood pressure P(3) at this time, the diastolic blood pressure P
(D) is a relational expression, p (D) = (3xP(7)-p
(3) }/2 incorrectly determines the diastolic blood pressure P (D).

In view of the above, the present invention provides, in the cuff pressure reduction process,
The correct diastolic blood pressure can be determined even when the time-series change in pulse wave amplitude is disturbed due to body movements (artifacts) of the person being measured, individual differences in the measurement site of the person being measured, electrical noise, etc. A method for determining diastolic blood pressure is provided.

[Means to solve the problem]

The gist of the present invention for achieving the above object is to calculate the temporary diastolic blood pressure P (d) from the systolic blood pressure P' (S) measured during the cuff pressure reduction process and the mean blood pressure P (M) using the relational formula %. The first diastolic blood pressure determination means calculates the comparative pulse wave amplitude H(D) by the pulse wave amplitude H(M) at the mean blood pressure P(M) and the diastolic blood pressure determination coefficient, and the relational expression % and a second diastolic blood pressure determination means that calculates the blood pressure according to the formula (%).

[Function] In this electronic blood pressure monitor, the cuff pressure P (
i) is equal to or lower than the provisional diastolic blood pressure P (d) calculated by the first diastolic blood pressure determining means, and the pulse wave amplitude H(i) is a comparative pulse wave calculated by the second diastolic blood pressure determining means. The cuff pressure P (i) when the amplitude falls below H (D) is defined as the diastolic blood pressure P (D).

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

FIG. 2 shows an example of blood pressure measurement using an electronic blood pressure monitor. A cuff 32 for blocking arterial blood is attached to the blood pressure measurement site 31 (for example, the upper arm) of the person being measured, a rubber tube 33 is connected to a part of the cuff 32, and the other end of the rubber tube 33 is connected to the measuring device body 34. The cuff 32 and the measuring device main body 34 are connected to each other, and fluid (for example, air) can be transferred between the cuff 32 and the measuring device main body 34 via the rubber tube 33. Hereinafter, a circuit in which a fluid (for example, air) moves will be referred to as a fluid circuit. FIG. 3 is a block diagram showing the internal structure of the main body.

First, the fluid circuit in the measuring instrument main body 34 will be explained. The fluid circuit within the measuring instrument main body 34 is branched into four. The first is a pressure sensor 35 that converts the pressure inside the cuff 32 into an electrical signal, the second is a slow exhaust valve 39 that gradually reduces the pressure inside the cuff 32, and the third is the pressure inside the cuff 32. Rapid exhaust valve 40 for rapidly depressurizing
The fourth is a pressure pump 41 for increasing the pressure within the cuff 32. Next, the electric circuit in the measuring instrument main body 4 will be explained. The pressure analog electrical signal converted by the pressure sensor 35 is converted into a digital signal by the A/D converter 36. This digital signal is C
The data is input to a microcomputer 37 composed of a PU, ROM, RAM, and the like. The microcomputer 37 also sends a pressurizing pump 4 for pressurizing the cuff 32.
A control signal for turning on and off the rapid exhaust valve 40 and a control signal for turning on and off the rapid exhaust valve 40 are output. On the front surface of the measuring device main body 34, an operation switch unit 42 is arranged, which controls blood pressure measurement by this electronic blood pressure monitor and is composed of a power switch, a start switch, a pressurization upper limit setting switch, etc. The signal is input to the microcomputer 37. Similarly, a display 38 for displaying measured results and the like is arranged on the front surface of the measuring instrument main body 34, and a display data signal is output from the microcomputer 37. The measuring instrument main body 34 has a built-in power supply unit 43, and when power is required for operating the microcomputer 37, the power supply unit 43 supplies power. This embodiment is a method generally called an automatic method in which cuff pressure is applied by the pressurizing pump 41, but it can also be applied to a method generally referred to as a manual method in which cuff pressure is manually performed.

FIG. 8 is a flowchart showing the flow of blood pressure measurement. Blood pressure measurement is started by the operation switch section 42.
O), the cuff pressure is increased by the pressure pump 41 (ST
I). The rapid exhaust valve 40 is closed during pressurization. When the cuff pressure reaches a predetermined pressure set by the operation switch unit 42 before the start of measurement (Sr2), the pressurization by the pressurizing pump 41 is stopped (5T3), and the slow exhaust valve 39 starts lowering the cuff pressure. (Sr1). As shown in Figure 4 above, oscillations (pulse waves) occur in the cuff pressure in response to arterial pulsation, and the systolic blood pressure (Sr1) and mean blood pressure P (M) are determined from the amplitude of this pulse wave.
(Sr6) and the diastolic blood pressure (Sr1) are determined, the results are displayed on the display unit 38 (Sr8), and the rapid exhaust valve 40 is opened to remove the pressure of the cuff 32 pressing on the measurement site (
Sr1), blood pressure measurement ends (STIO).

FIG. 4 is a diagram showing changes in cuff pressure during a slow decompression process. FIG. 5 is a diagram showing vibration components extracted and separated from the cuff pressure signal of FIG. 4.

FIG. 1 is a flowchart showing the flow of blood pressure measurement according to the present invention. Systolic blood pressure determination (Sr1) from the start of measurement (STO)
) is the same as shown in FIG. The method for determining systolic blood pressure is similar to the method for determining diastolic blood pressure described above, using two methods: an actual measurement method in which the cuff pressure at which the rate of increase in pulse wave amplitude per beat is the maximum is taken as the systolic blood pressure, and a method in which the maximum pulse wave amplitude H (M ) is multiplied by the systolic blood pressure determination coefficient G, and the cuff pressure when the pulse wave amplitude exceeds the product of H(M) and G is the systolic blood pressure. However, in this example, the pulse wave amplitude is Amplitude comparison method was used. FIG. 11 is a diagram showing the logic (algorithm) for determining systolic blood pressure using the pulse wave amplitude comparison method.

The algorithm for determining the systolic blood pressure will be explained with reference to FIG. As a preparatory step, the maximum pulse wave amplitude H (M), the pressure P (M) at the maximum pulse wave amplitude, and counter i and counter j are cleared to zero (STII). When the pulse wave is detected (ST12), the pulse wave starting cuff pressure P is set to P(i), and the pulse wave amplitude H is set to H(i) (ST13) L, i are set to 1.
Increment (ST14) L, if i is 1 (ST
I5) returns to 5T12. If i is not 1 (ST1
In step 5), it is determined whether H(i) exceeds H(M) (5T16), and if it does not, the process moves to 5T18.

If it exceeds the maximum pulse wave amplitude, update the width H(M) (ST17). Clear the counter j to zero (STI 8), and H(j) is the systolic blood pressure determination coefficient. Determine whether the product of G and maximum pulse wave amplitude H (M) is not exceeded (5T19), and if it is not, set j to 1.
Increment 5T20), then determine whether j is equal to i 5T21), and if not, return to 5T19. If they are equal, return to 5T12. At 5T19, H(j) is the maximum pulse wave amplitude H(M) and the systolic blood pressure determination coefficient G
The pulse wave starting cuff pressure P (i) when the product exceeds the product of P (i) is defined as the systolic blood pressure P (S) (Sr22).

After determining the systolic blood pressure, the diastolic blood pressure is determined.

The algorithm for determining the diastolic blood pressure will be explained with reference to FIG. The process from the start of measurement (STO) to the determination of systolic blood pressure (Sr1) is the same as that shown in FIG. When the pulse wave is detected (Sr23), the pulse wave starting cuff pressure P is set to P(i), and the pulse wave amplitude H is set to H(i). (Sr24) L, i is incremented by one (Sr25) L, H( 5T26) to determine whether i) does not exceed H(M), and if it does not, proceed to S"T28. If it does exceed H(M).
) is updated (Sr27). The tentative diastolic blood pressure P (d) is expressed as the relational expression, P (d) = (3('M) - P (S) ) /2
Calculate by (Sr2B)L, and multiply the maximum pulse wave amplitude H(M) by the diastolic blood pressure determination coefficient to obtain the comparison pulse wave amplitude H(D) (Sr29). The cuff pressure P (i) is the temporary diastolic blood pressure P (
d) (S730) If L, P(i) exceeds P(d), the process returns to Sr23. P (
If i) is less than P (d), it is determined whether the pulse wave amplitude H(i) exceeds the comparative pulse wave amplitude H(D) (ST31
). 5T23 if H(i) exceeds H(D)
Return to If H(i) is less than or equal to H(D), set pulse wave starting cuff pressure P(i) to diastolic blood pressure P(D) (ST32)
. Measurement ends from blood pressure display (Sr8) after determining diastolic blood pressure (
STIO) is the same as in FIG. Figure 9 and 1
An algorithm by which the present invention can avoid mistakes in determining the diastolic blood pressure caused by only one of the pulse wave amplitude comparison method and the estimation calculation method when determining the diastolic blood pressure will be described with reference to FIG. First, the pulse wave amplitude comparison method will be explained with reference to FIG. With only the pulse wave amplitude comparison method, when a significantly small pulse wave is measured from the regular decreasing process of pulse wave amplitude as at time 11 in Fig. 9, the pulse wave amplitude H indicating the maximum pulse wave amplitude is
If the product of (9) and the diastolic blood pressure determination coefficient G is greater than H(11), the cuff pressure at H(11) is determined by the diastolic blood pressure P (D).
And so. However, as in the present invention, if the diastolic blood pressure is determined by logical product with the estimation calculation method, cuff pressure P (i
) is less than the hypothetical diastolic blood pressure calculated by P(M) (=P (9)) and systolic blood pressure p (s), the diastolic blood pressure is not determined, so the example of FIG. 9 can be avoided. In addition, with only the estimation calculation method, when a significantly small pulse wave is measured from the regular pulse wave amplitude rising process as at time 8 in Figure 10, the maximum pulse wave amplitude H(M) [=H(7)] Even in the case where an incorrect diastolic blood pressure is calculated using the relational expression p (D) = {3×P (7) - P (S)), the present invention can be applied to If the diastolic blood pressure is determined by logical product with the pulse wave amplitude comparison method, the pulse wave amplitude H(7) at time 8 in FIG. 8) is large, the error in determining the diastolic blood pressure at time 8 in FIG. 10 can be avoided.

〔Effect of the invention〕

According to this invention, in an electronic sphygmomanometer using a vibration method that determines blood pressure by vibration of cuff pressure, body movements (artifacts) of a person to be measured during measurement, individual differences in the measurement site of a person to be measured, electrical noise, etc. In this case, the amplitude of the pulse wave due to the arterial pulsation of the cuff pressure was measured during the pressure change process. From the systolic blood pressure P (S) and the mean blood pressure P (M), the relational expression, P (d) = (3xP (M
)-p (s) }/2, the first diastolic blood pressure determining means calculates the provisional diastolic blood pressure P (d), and the comparative pulse wave amplitude H(D) is calculated from the mean blood pressure P
A second diastolic blood pressure determining means calculates the pulse wave amplitude H(M) at time (M) and the diastolic blood pressure determination coefficient from the relational expression, H(D) = H(M) XK, and the pressure change The cuff pressure P (i) during the process is equal to or lower than the temporary diastolic blood pressure P (d) calculated by the first diastolic blood pressure determining means, and the pulse wave amplitude H (i) is By setting the cuff pressure P(i) when it falls below the comparative pulse wave amplitude H(D) calculated by as the diastolic blood pressure P(D), even if the above-mentioned time-series change in pulse wave amplitude is disturbed. , can accurately determine diastolic blood pressure.

[Brief explanation of drawings]

Figure 1 is a flowchart of the diastolic blood pressure determination method according to the present invention, Figure 2 is an example of blood pressure measurement, Figure 3 is a block diagram of the same as above, and Figure 4 is when the cuff is in the slow decompression process after pressurizing. FIG. 5, a diagram showing vibrations in cuff pressure, is a diagram showing vibrations extracted and separated from FIG. 4, and is a diagram showing ideal vibration changes. Figure 6 is a diagram showing extracted and separated vibrations. When the maximum pulse wave amplitude is small, Figure 7 is a diagram showing extracted and separated pulse waves. When the time series change is gentle, Figure 8 is a diagram showing extracted and separated vibrations. This is a flowchart showing the flow of blood pressure measurement, and FIG. 9 shows an example in which an error occurs in determining the diastolic blood pressure using the pulse wave amplitude comparison method.
FIG. 10 shows an example in which an error occurs in determining the diastolic blood pressure using the estimation calculation method, and FIG. 11 is a flowchart showing a method for determining the systolic blood pressure using the pulse wave amplitude comparison method. Blood pressure measurement site... Cuff... 32, Pressure sensor... A/D converter... Slow exhaust valve... Rapid exhaust valve... Pressure pump... ・ 31, ・ 35, ・ 36. 39. 40. 41゜ 1st Figure Time 5 Figure Time Opening Figure Prisoner Figure r m 0th 4th hour

Claims (2)

[Claims] (1) The cuff attached to the blood pressure measurement site of the person to be measured, the pressurizing pump to increase the pressure inside the cuff, and the slow exhaust valve to gradually reduce the pressure inside the cuff, and the measurement is completed. After that, there is a rapid exhaust valve that rapidly reduces the pressure inside the cuff, a pressure sensor that converts the pressure inside the cuff into an electrical signal, and an A/D converter that converts the pressure sensor signal into a digital value.
A D converter, a pulse wave amplitude detecting means for detecting pulse wave amplitude in a cuff pressure change process, and a blood pressure value determining means for determining blood pressure from the pulse wave amplitude detecting means and the cuff pressure detected by the pressure sensor. In the electronic sphygmomanometer, the relational expression P(d) = {3×P (M)-P(S)}/2, and a comparison pulse wave amplitude H(D).
from the pulse wave amplitude H(M) at the mean blood pressure P(M) and the diastolic blood pressure determination coefficient K using the relational expression H(D)=H(M)×K. and the cuff pressure P(i) during the pressure change process is equal to or lower than the provisional diastolic blood pressure P(d) calculated by the first diastolic blood pressure determination means, and the pulse wave amplitude H(i) is the second An electronic sphygmomanometer characterized in that the cuff pressure P(i) when the cuff pressure becomes equal to or less than the comparative pulse wave amplitude H(D) calculated by the diastolic blood pressure determining means is set as the diastolic blood pressure. (2) The electronic blood pressure monitor according to claim 1, wherein the diastolic blood pressure determination coefficient K is 0.5 to 0.8.