JP2006247216A - Automated oscillometric blood pressure-measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automated oscillometric blood pressure-measuring apparatus capable of shortening measurement time while maintaining high measurement precision. <P>SOLUTION: The automated oscillometric blood pressure-measuring apparatus has a cuff wound around a predetermined part of the living body, and determines blood pressure value BP on the basis of amplitude change of cuff pulse waves generated in the cuff while reducing cuff pressure PC gradually. In the apparatus, the speed for reducing cuff pressure PC gradually is kept constant at 11-13 mmHg/sec or 8-9 mmHg/sec. Since the cuff pressure PC reducing speed is higher than conventional speed (about 5 mmHg/sec), the measurement time is shortened. In addition, because the cuff pressure reducing speed is constant, the apparatus acquires a more accurate blood pressure value BP at higher pressure reducing speed compared to a conventional apparatus which controls reducing amount of cuff pressure PC per one beat to be constant automatically. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an oscillometric automatic blood pressure measurement device, and more particularly to a technique for shortening the measurement time by increasing the cuff change rate.

  As a blood pressure measuring device that automatically measures a blood pressure value of a living body, an automatic blood pressure measuring device that automatically measures blood pressure by a so-called oscillometric method is known. An oscillometric automatic blood pressure measuring device winds a cuff around a predetermined part of a living body, boosts the pressure of the cuff (hereinafter referred to as cuff pressure) to a preset target pressure value, and then increases the cuff pressure. Decrease blood pressure gradually, collect cuff pulse wave generated in cuff in the slow pressure decrease process, and determine blood pressure value using pre-stored oscillometric algorithm based on change of amplitude of cuff pulse wave is doing.

In order to obtain a highly accurate blood pressure value in an oscillometric automatic blood pressure measurement device, it has been considered important to make the amount of cuff pressure lowered per beat constant. Therefore, an automatic blood pressure measurement device is widely used that controls the pressure reduction rate of the cuff pressure in response to fluctuations in the heart rate cycle during blood pressure measurement to automatically and constantly control the amount of cuff pressure reduction per beat. (For example, Patent Document 1). In addition, when the amount of pressure reduction of cuff pressure is controlled to be, for example, 5 mmHg / beat, the pressure reduction speed per hour usually varies in the range of 4 to 7 mmHg / sec.
Japanese Examined Patent Publication No. 1-4617

  By the way, it is preferable that the blood pressure measurement time is as short as possible. In order to shorten the measurement time in blood pressure measurement using an oscillometric automatic blood pressure measurement device, it is necessary to increase the cuff pressure gradually decreasing rate. However, if the conventional device is used to simply increase the gradually decreasing rate, The accuracy of the determined blood pressure value is lowered and is not practical.

  The present invention has been made against the background of the above circumstances, and an object of the present invention is to provide an oscillometric automatic blood pressure measurement device capable of reducing measurement time while maintaining high measurement accuracy. There is.

  As a result of various studies to achieve the above object, the present inventor has found the following knowledge. That is, it was found that the amplitude of the cuff pulse wave detected during the gradual change of the cuff pressure is affected by the step-down speed, and that the amplitude of the cuff pulse wave decreases as the step-down speed increases. FIG. 1 is a diagram showing this, and the magnitude of the cuff pulse wave detected when the cuff pressure is gradually decreased at three constant speeds of 5, 10, and 15 mmHg / sec at rest for the same subject. It shows. In FIG. 1, the waveform at each step-down speed is shown with the time axis shifted. Further, FIG. 1 shows only one measurement result for each step-down speed, but when each step-down speed was measured 20 times, good reproducibility was obtained for any step-down speed.

  It can be seen from FIG. 1 that the changing speed of the cuff pressure affects the amplitude. In the oscillometric algorithm, since the blood pressure value is determined based on the change in the amplitude of the cuff pulse wave, in order to obtain a precise blood pressure value, it is necessary to make the slow pressure decrease rate constant, It is found that if the pressure reduction rate per hour is changed in order to make the amount of pressure reduction of the cuff pressure per beat constant, the amplitude will change due to the change in the pressure reduction speed, and an accurate blood pressure value cannot be obtained. It was. The present invention has been made based on such knowledge.

  That is, the first invention for achieving the above object includes a cuff wound around a predetermined part of a living body, and the amplitude of the cuff pulse wave generated in the cuff in the process of gradually changing the compression pressure of the cuff. An oscillometric automatic blood pressure measurement device that determines a blood pressure value of the living body based on a change, and controls a speed change rate of the compression pressure of the cuff so as to be a constant speed of 7 mmHg / sec or more. It is characterized by that.

  According to a second invention, in the automatic blood pressure measurement device according to the first invention, the compression pressure of the cuff is the maximum blood pressure based on the pulse rate and pulse pressure of the living body obtained before the start of the gradual change of the compression pressure of the cuff. The speed of the speed change is determined so that a cuff pulse wave of 3 beats or more is detected during the speed change between the value and the minimum blood pressure value.

  According to a third aspect of the present invention, there is provided an automatic blood pressure measurement apparatus according to the first or second aspect of the present invention, based on the cuff pulse wave amplitude sequentially obtained in the process of gradually changing the cuff compression pressure. An envelope curve indicating a change in the amplitude of the pulse wave is created, and at least one of the maximum blood pressure value and the minimum blood pressure value is determined as a cuff compression pressure whose amplitude is a predetermined ratio of the maximum amplitude in the envelope. To do.

  According to a fourth invention, in the automatic blood pressure measurement device according to the third invention, a cubic function is determined on the basis of the amplitudes of four cuff pulse waves obtained continuously in the process of gradually changing the compression pressure of the cuff. The envelope is created by interpolating between the vertices of the center two amplitudes of the amplitude of the cuff pulse wave with its cubic function.

  According to the first aspect of the invention, since the slow change speed of the cuff compression pressure is 7 mmHg / sec or more, the measurement time is short, and the slow pressure drop speed is constant, so A good blood pressure is obtained.

  According to the second aspect of the present invention, the measurement time can be shortened as much as possible within a range in which the minimum number of beats necessary for determining an accurate blood pressure value can be obtained.

  According to the third invention, in the envelope created based on the amplitude of the cuff pulse wave, not only the cuff pressure corresponding to the amplitude of each cuff pulse wave actually detected, but also the cuff pulse wave actually detected Since the cuff pressure corresponding to the amplitude of the cuff is determined as the maximum blood pressure value or the minimum blood pressure value, the decrease in blood pressure measurement accuracy due to the decrease in the number of cuff pulse waves obtained during the cuff pressure gradual change period is suppressed. Is done.

  According to the fourth invention, the created envelope is a curve having one inflection point up to and after the peak, and a point having a pair of inflection points and an upper peak therebetween, Since the envelope is the same as when the cuff pressure gradually changes at a rate of about 5 mmHg / sec as in the prior art, the blood pressure due to the reduced number of cuff pulse waves obtained during the cuff pressure slowly changing period. Decrease in value accuracy is suppressed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 2 is a block diagram showing a circuit configuration of an oscillometric automatic blood pressure measurement device (hereinafter simply referred to as an automatic blood pressure measurement device) 10 to which the present invention is applied.

  In FIG. 2, the cuff 12 has a rubber bag in a cloth band bag and is wound around the upper arm portion 14. A pressure sensor 16 and a pressure regulating valve 18 are connected to the cuff 12 via a pipe 20, respectively. An air pump 24 is connected to the pressure regulating valve 18 via a pipe 22. The pressure regulating valve 18 regulates the pressure in the cuff 12 by regulating the high-pressure air generated by the air pump 24 and supplying it to the cuff 12 or exhausting the air in the cuff 12.

  The pressure sensor 16 detects the pressure in the cuff 12 and supplies a pressure signal SP representing the pressure to the static pressure discrimination circuit 26 and the pulse wave discrimination circuit 28, respectively. The static pressure discriminating circuit 26 includes a low-pass filter, and discriminates the cuff pressure signal SC representing the steady pressure included in the pressure signal SP, that is, the compression pressure of the cuff 12 (that is, the cuff pressure PC), and uses the cuff pressure signal SC. This is supplied to the electronic control unit 32 via the A / D converter 30. The pulse wave discrimination circuit 28 includes a band pass filter having a signal pass band of about 1 to 30 Hz, for example, and discriminates the cuff pulse wave signal SM, which is a vibration component of the pressure signal SP, and converts the cuff pulse wave signal SM to A / This is supplied to the electronic control unit 32 via the D converter 34. The cuff pulse wave signal SM represents a cuff pulse wave because it is transmitted to the cuff 12 from a brachial artery (not shown) and generated in the cuff.

The electronic control unit 32 includes a CPU 36, a ROM 38, a RAM 40, and a so-called microcomputer having an I / O port (not shown). The CPU 36 uses a memory function of the RAM 40 according to a program stored in advance in the ROM 38. However, by executing the signal processing, the drive signal is output to control the air pump 24, and the valve opening degree control signal (voltage) is output to control the valve opening degree of the pressure regulating valve 18. The CPU 36 controls the cuff pressure PC by controlling the air pump 24 and the pressure regulating valve 18. Further, by executing the function shown in FIG. 2, the CPU 36 increases the cuff pressure PC to a pressure higher than the measurement subject's maximum blood pressure BP _SYS , and then gradually decreases the cuff pressure PC while gradually decreasing the cuff pressure PC. A blood pressure value BP is determined based on the obtained cuff pulse wave, and the determined blood pressure value BP is displayed on the display 42.

FIG. 3 is a functional block diagram showing the main part of the control function of the CPU 36. The cuff pressure control means 50 determines the cuff pressure PC based on the cuff pressure signal SC sequentially supplied from the static pressure discriminating circuit 26, and controls the pressure regulating valve 18 and the air pump 24 to control the cuff pressure PC as follows. To control. That is, the cuff pressure PC is rapidly increased to a pressure increase target pressure value PC _M (for example, 180 mmHg) set in advance to a value higher than the maximum blood pressure value BP _SYS in the upper arm portion 14, and then the pressure increase target pressure value PC _M After the execution of the cuff pressure stabilization process for stabilizing the cuff pressure PC, a constant step-down speed of 7 mmHg / sec or more determined before the start of the step-down step until the predetermined step-down step-down condition is satisfied. Then, the cuff pressure PC is gradually reduced, and when the condition for ending the slow pressure reduction is satisfied, the cuff pressure PC is discharged to the atmospheric pressure.

The envelope creation means 52 sequentially determines the amplitude of the cuff pulse wave while the cuff pressure control means 50 gradually decreases the cuff pressure PC, and generates an envelope based on the amplitude of the cuff pulse wave of four or more beats. create. The blood pressure value determining means 54 determines the maximum blood pressure value BP _SYS , the minimum blood pressure value BP _DIA , and the average blood pressure value BP _MEAN based on the envelope created by the envelope creating means 52, and the determined maximum blood pressure value BP _SYS or the like is displayed on the display 42.

  FIG. 4 is a flowchart for explaining the specific processing contents of the main part of the control function of the CPU 36. FIG. 5 is a diagram showing an example of changes in the cuff pressure PC and the cuff pulse wave in the control according to this flowchart. is there. This flowchart starts when a measurement start button (not shown) is pressed.

First, in step S1 (hereinafter, step is omitted), the difference between the maximum blood pressure value BP _SYS and the minimum blood pressure value BP _DIA obtained by the previous measurement from two preset slow pressure reduction rate candidates ( That is, based on the pulse pressure PP) and the pulse rate HR, the slow pressure decrease rate in the current measurement is determined. In the present embodiment, 11 to 13 mmHg / sec and 7 to 8 mmHg / sec are set as slow pressure reduction speed candidates, and the cuff pressure PC is calculated from the pulse pressure PP and the pulse rate HR obtained by the previous measurement. Is selected so that a pulse wave of 4 beats or more is detected while the blood pressure decreases from the systolic blood pressure value BP _SYS to the systolic blood pressure value BP _DIA . Even if the heart rate HR at the time of the previous measurement and the heart rate HR at the time of the current measurement are slightly different, the pulse of at least 3 beats while the cuff pressure PC actually decreases from the maximum blood pressure value BP _SYS to the minimum blood pressure value BP _DIA. Expect to be able to collect waves). However, when there is no previous measurement value, one preset slow speed reduction speed candidate is selected. Each of the slow speed decrease speed candidates has a range of 1 mmHg, which means an allowable range of the actual slow speed decrease speed set in S5 described later. In this embodiment, the number of slow speed decrease rate candidates is two. However, more candidates may be set, or only one candidate may be set.

In the subsequent S2, the air pump 24 is activated and the pressure regulating valve 18 is controlled to start the rapid pressure increase of the cuff pressure PC (t0 in FIG. 5). Subsequently, at S3, the cuff pressure PC is determined whether exceeds the target pressure PC _M set to 180 mmHg. While the determination of S3 is denied, the determination of S3 is repeatedly executed and the rapid increase of the cuff pressure PC is continued.

  On the other hand, if the determination in S3 is affirmative, the air pump 24 is temporarily stopped in S4, and then the cuff pressure PC stabilization process is executed (t1 to t2 in FIG. 5). In this process, immediately after the rapid increase of the cuff pressure PC, the cuff pressure PC is not stabilized and a decrease in the cuff pressure PC is observed. Therefore, when the cuff pressure PC is reduced by 1 mmHg or more, the air pump 24 is immediately restarted. This process is activated to compensate for the step-down amount, and this process is executed until the cuff pressure PC is stabilized. The time required for this process is about 1 to 2 seconds.

  When the stabilization process of the cuff pressure PC is completed, the initial exhaust process control is subsequently executed in S5. In this control, the valve opening control voltage of the pressure regulating valve 18 is gradually increased to gradually release the pressure regulating valve 18, and the amount of pressure reduction at a predetermined interval (for example, 200 msec) at this time is set to be smaller than that interval. This is a control for monitoring a valve opening control voltage that is monitored every sufficiently short monitoring period (for example, 4 msec) and that can obtain the constant slow step-down speed determined in S1.

  When the valve opening control voltage is determined in S5, the slow pressure reduction by the constant exhaust control is started in the subsequent S6 (t3 in FIG. 5). In this constant exhaust control, the slow pressure reduction is started at the valve opening control voltage determined in S5, and thereafter, in accordance with a preset correction formula in which the correction amount is determined based on the actual pressure reduction amount, This is a control to maintain a constant gradual step-down speed by correcting the valve opening control voltage, and the cuff pressure PC is lowered if the valve opening degree during the gradual step-down is kept constant. Therefore, the correction formula includes an offset function (or array) for gradually increasing the valve opening as the cuff pressure PC decreases below the predetermined cuff pressure PC. Yes.

  Subsequently, a blood pressure measurement routine (S7 to S12) for measuring a signal for determining the blood pressure value BP is executed. First, in S7, the cuff pressure signal SC and the cuff pulse wave signal SM are read every predetermined sampling period. In S8, it is determined whether or not a signal for one beat has been read. If this determination is negative, the signal reading is continued by repeating S7.

  On the other hand, if the determination in S8 is affirmative, in the subsequent S9, the amplitude of the cuff pulse wave for one beat is determined. In subsequent S10, an envelope is created based on the amplitude determined in S9. FIG. 6 is a diagram illustrating an example of an envelope. As shown in FIG. 6, the envelope is a two-dimensional graph having a cuff pressure PC component and a cuff pulse wave amplitude component, and is a line connecting vertices of each cuff pulse wave amplitude indicated by a straight line. This envelope is created by interpolating between vertices of adjacent cuff pulse wave amplitudes by a cubic curve. More specifically, a cubic curve is determined based on the coordinates of the vertices of four consecutive cuff pulse wave amplitudes (for example, P1 to P4 shown in FIG. 6), and the central two vertices (P2, P3) in the cubic curve. Interpolating between them, and then determining a cubic curve based on the coordinates of four consecutive vertices (P2 to P5), one of which is the end of the two central vertices, and the two central vertices (P3, The envelope is created by repeating the process of interpolating with a cubic curve determined between P4). Alternatively, first, a cubic curve is determined based on the coordinates of four continuous cuff pulse wave amplitude vertices (for example, P1 to P4 shown in FIG. 6), and between the two vertices at the center (P2, P3) in the cubic curve. Are interpolated, three consecutive cuff pulse wave amplitude vertices (for example, P3 to P5) including at least one of the two vertices (P2, P3), and end points (P2, P3) of the section interpolated by the previous processing The cubic function is determined based on the slope at the end point (P3) adjacent to the vertex that is not yet interpolated, and the section (P3 to P5) adjacent to the section interpolated by the previous processing is interpolated. Create an envelope by repeating the process.

In subsequent S11, based on the envelope created in S10, the blood pressure value BP is determined as follows. The average blood pressure value BP _MEAN is a pressure obtained by subtracting a pressure reduction amount per beat or a correction value determined based on the pressure reduction amount from the cuff pressure PC indicating the maximum value (maximum amplitude) of the envelope. The maximum blood pressure value BP _SYS is a cuff pressure PC that is higher than the average blood pressure value BP _{MEAN and} indicates a predetermined ratio (here, 60%) of the maximum value of the envelope. The minimum blood pressure value BP _DIA is a cuff pressure PC that is lower than the average blood pressure value BP _{MEAN and} indicates a predetermined ratio (58% in this case) of the maximum value of the envelope. Therefore, the maximum blood pressure value BP _SYS and the minimum blood pressure value BP _DIA are not limited to the cuff pressure PC corresponding to the amplitude of the cuff pulse wave actually detected.

In subsequent S12, it is determined whether or not a preset condition for gradual pressure reduction is satisfied. In this embodiment, the slow pressure reduction termination condition is (1) after the maximum amplitude, n beats or more (n is 4 for example), the amplitude is decreased from the previous beat, or n + 1 beats, The amplitude is reduced or equal compared to before one beat, (2) the latest amplitude is 60% or less of the average blood pressure value BP _MEAN , (3) the pulse wave after the above condition (1) is satisfied If the upper peak value is smaller than the upper peak value of the pulse wave one beat before, and if all the conditions are satisfied, it is determined that the slow pressure reduction termination condition is satisfied.

  If the determination in S12 is negative, the blood pressure measurement routine is continued by repeatedly executing the steps after S7. On the other hand, if the determination in S12 is affirmative, in S13, the opening of the pressure regulating valve 18 is maximized and the cuff pressure PC is exhausted to atmospheric pressure. Subsequently, in S14, the blood pressure measurement routine in S7 to S12 is performed. The blood pressure value BP determined by executing is displayed on the display 42. In the flowchart of FIG. 4, S1 to S6 and S12 to S13 correspond to the cuff pressure control means 50, S7 to S10 correspond to the envelope creation means 52, and S11 and S14 correspond to the blood pressure value determination means 54. .

  Next, the blood pressure value BP measured by controlling the pressure reduction amount of the cuff pressure PC per beat to be automatically constant (here, 5 mmHg / beat) as in the prior art, and shorter than the conventional one by the present invention. An experiment in which the blood pressure value BP measured over time is compared with the blood pressure value measured invasively will be described.

  Open blood pressure was measured continuously by inserting a catheter into the patient's radial artery. On the other hand, blood pressure measurement by the oscillometric method is performed by wrapping a cuff around the upper arm of the other arm where a catheter is not inserted, and a pipe extending from the cuff through a three-way valve to measure blood pressure by a conventional method, The apparatus connected to both of the apparatuses for measuring blood pressure according to the invention was used, the measurement interval was set to 5 minutes, and the blood pressure measurement by the conventional method and the short-time measurement of the present invention were alternately performed. Therefore, the measurement by the conventional method and the short time measurement of the present invention were measured at intervals of 10 minutes. There were 23 test subjects, and the number of measurements for each test subject was between 16 and 48 sets, assuming that the measurement by the conventional method and the short-time measurement of the present invention were one set. The measurement time of the present invention is about 17 seconds on the average, while that of the conventional measurement is about 28 seconds on average. The average measurement time is 10 seconds or more shorter in the present invention.

A linear regression line of the highest blood pressure value BP _SYS (conv) by the conventional measurement with respect to the highest blood pressure value BP _SYS (inv) by the invasive measurement, and the short time of the present invention for the highest blood pressure value BP _SYS (inv) by the invasive measurement. The linear regression lines of the systolic blood pressure BP _SYS (fast) by measurement are as shown in Equations 1 and 2, and R ² = 0.86 and 0.87, respectively. The difference from the open measurement was 2.1 ± 7.5 mmHg in the conventional measurement, and 1.4 ± 7.3 mmHg in the short-time measurement of the present invention. Therefore, it can be said that the systolic blood pressure value BP _SYS (conv) measured by the conventional measurement and the systolic blood pressure value BP _SYS (fast) according to the present invention have substantially the same accuracy.
(Formula 1) BP _SYS (conv) = 0.84 BP _SYS (inv) +20.3
(Formula 2) BP _SYS (fast) = 0.84 BP _SYS (inv) +20.2

Further, the present invention relative to the linear regression line of diastolic blood pressure _BP DIA by conventional measurements on the diastolic blood pressure value by invasive measurement _{BP DIA (inv) (conv)} , and the diastolic blood pressure value _BP DIA by invasive measurements (inv) The linear regression lines of the diastolic blood pressure BP _DIA (fast) by short-time measurement are as shown in Equation 3 and Equation 4, and R ² = 0.67 and 0.75, respectively. Further, the difference from the open measurement is 5.0 ± 6.8 mmHg in the conventional measurement, and 4.9 ± 5.8 mmHg in the short time measurement of the present invention, and the measurement time is shortened in the present invention. Nevertheless, it can be seen that the minimum blood pressure BP _DIA has better measurement accuracy than the conventional measurement.
(Formula 3) BP _DIA (conv) = 0.92 BP _DIA (inv) +9.6
(Formula 4) BP _DIA (fast) = 0.96 BP _DIA (inv) +7.1

  As described above, according to the present embodiment, the slow change rate of the cuff pressure PC is set to 11 to 13 mmHg / sec or 8 to 9 mmHg / sec. Is constant, so that an accurate blood pressure value BP can be obtained.

Further, according to the present embodiment, based on the blood pressure value BP measured last time, a pulse wave of 4 beats or more is detected while the cuff pressure PC decreases from the maximum blood pressure value BP _SYS to the minimum blood pressure value BP _DIA. Therefore, the measurement time can be shortened as much as possible within a range in which the minimum number of beats necessary for determining the accurate blood pressure value BP can be obtained.

According to the present embodiment, in the envelope created based on the amplitude of the cuff pulse wave, not only the cuff pressure PC corresponding to the amplitude of each cuff pulse wave actually detected, but also the amplitude of the cuff pulse wave. The corresponding cuff pressure PC is also determined as the maximum blood pressure value BP _SYS and the minimum blood pressure value BP _DIA . In addition, according to the present embodiment, since the amplitude vertices are interpolated with a cubic function, the created envelope is a curve having one inflection point up to and after the peak. At a point where there is a pair of inflection points and an upper peak between them, the envelope curve is the same as that when the slow change rate of the cuff pressure PC is about 5 mmHg / sec as in the prior art. As a result, a decrease in blood pressure measurement accuracy due to a decrease in the number of cuff pulse waves obtained during the gradual change period of the cuff pressure PC is suppressed.

  As mentioned above, although the Example of this invention was described in detail based on drawing, this invention is applied also in another aspect.

  For example, in the above-described embodiment, the example in which the cuff pressure PC is gradually decreased as the gradual change of the cuff pressure PC during blood pressure measurement has been described. However, the blood pressure may be measured during the gradual increase in pressure.

  In the above-described embodiment, the pulse rate HR at the time of the previous measurement is used as the pulse rate HR for selecting the slow pressure reduction speed. However, the pulse rate determined based on the pulse wave obtained in the pressurization process is used. HR may be used, and when an apparatus capable of obtaining a signal synchronized with a pulse, such as an electrocardiograph or a volume pulse wave detection device (plethysmograph), is used together with the automatic blood pressure measurement device 10, You may use the pulse rate HR determined based on the signal obtained from those apparatuses. Since the pulse rate HR and the pulse cycle correspond one-to-one, the pulse cycle may be used instead of the pulse rate HR. When the pulse period is used, it can be considered that the pulse rate HR is substantially used.

  In the above-described embodiment, the amplitudes are interpolated between the vertices by a cubic function, but may be interpolated by a function other than a straight line or a cubic function.

In addition, the method of determining the blood pressure value BP based on the envelope is not limited to the above-described embodiment. For example, the maximum blood pressure value BP _SYS is set to a point where the rate of change in amplitude exceeds a predetermined criterion value in the envelope (that is, The cuff pressure PC corresponding to the rising point of the envelope) or the cuff pressure PC corresponding to the pair of maximum inclination points on the envelope is set to the higher side, or the average blood pressure value BP _MEAN is set to a point indicating the maximum value of the envelope. Corresponding cuff pressure PC or diastolic blood pressure BP _DIA is applied to the cuff pressure PC corresponding to the inflection point (the falling point of the envelope) or the pair of maximum slope points on the envelope. Various determination methods can be used, such as the lower side of the corresponding cuff pressure PC.

  Further, in the above-described embodiment, there are two candidates for the slow speed reduction rate, and each candidate is 7 mmHg / sec or more, but the number of candidates may be three or more, and among the plurality of candidates, May be 7 mmHg / sec or less. Further, an equation for determining the slow pressure decrease rate based on the pulse pressure and the heart rate HR may be stored, and the slow pressure decrease rate may be determined based on the equation.

Further, in the above-described embodiment, even if the heart rate HR slightly varies, a pulse wave of at least 3 beats is collected while the cuff pressure PC decreases from the maximum blood pressure value BP _SYS to the minimum blood pressure value BP _DIA in actual measurement. In order to be able to do so, as a precaution, the slow pressure reduction speed was set to a speed at which a pulse wave of 4 beats or more was detected in the calculation, but the cuff pressure PC was calculated from the maximum blood pressure value BP _SYS. While decreasing to the minimum blood pressure value BP _DIA , the slow pressure decrease rate may be set so that a pulse wave of 3 beats is detected in the calculation.

  In the above-described embodiment, the cuff 12 is attached to the upper arm portion 14, but may be attached to other parts, for example, an ankle or thigh.

  The above description is only an embodiment, and the present invention can be implemented in variously modified and improved forms based on the knowledge of those skilled in the art.

It is a figure which shows the magnitude | size of the cuff pulse wave detected when the cuff pressure is gradually reduced at three constant speeds of 5, 10, and 15 mmHg / sec at rest for the same subject. It is a block diagram which shows the circuit structure of the oscillometric type automatic blood pressure measuring device to which this invention was applied. It is a functional block diagram which shows the principal part of the control function of CPU of FIG. It is a flowchart explaining the specific processing content of the principal part of the control function of CPU. It is a figure which shows an example of the change of the cuff pressure PC and the cuff pulse wave in the control according to the flowchart of FIG. It is a figure which shows an example of the envelope created in S10 of FIG.

Explanation of symbols

10: oscillometric automatic blood pressure measurement device 12: cuff 14: upper arm 50: cuff pressure control means 52: envelope creation means 54: blood pressure value determination means

Claims (4)

An oscilloscope comprising a cuff wound around a predetermined part of a living body, and determining a blood pressure value of the living body based on a change in amplitude of a cuff pulse wave generated in the cuff in a process of gradually changing the compression pressure of the cuff A metric type automatic blood pressure measuring device,
An oscillometric automatic blood pressure measuring apparatus, wherein the gradual change speed of the compression pressure of the cuff is controlled to be a constant speed of 7 mmHg / sec or more. While the pressure of the cuff gradually changes between the maximum blood pressure value and the minimum blood pressure value based on the pulse rate and pulse pressure of the living body obtained before the start of the gradual change of the compression pressure of the cuff. The oscillometric automatic blood pressure measurement apparatus according to claim 1, wherein the speed of the slow change is determined so that a cuff pulse wave of 3 beats or more is detected. Based on the cuff pulse wave amplitude sequentially obtained in the process of gradually changing the cuff compression pressure, an envelope showing the change in the cuff pulse wave amplitude with respect to the change in the cuff compression pressure is created. 3. The oscillometric automatic blood pressure measuring device according to claim 1, wherein at least one of the blood pressure values is determined as a cuff compression pressure whose amplitude is a predetermined ratio of the maximum amplitude in the envelope. A cubic function is determined based on the amplitudes of the four cuff pulse waves continuously obtained in the process of gradually changing the compression pressure of the cuff, and the peak of the center two amplitudes of the amplitudes of the four cuff pulse waves 4. The oscillometric automatic blood pressure measuring apparatus according to claim 3, wherein the envelope is created by interpolating a gap with the cubic function.

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