JP5146994B2 - Blood pressure measurement device and control method thereof - Google Patents

Description

  The present invention relates to a blood pressure measurement technique, and particularly relates to provision of information related to the reliability of data used to derive a blood pressure value.

  Blood pressure measurement is very important in the treatment of hypertension. According to the WHO / ISH guidelines for hypertension treatment, the degree of hypertension is classified according to the blood pressure value in units of 5 mmHg, and treatment methods suitable for each are recommended. Therefore, whether or not appropriate treatment can be performed depends on the measured blood pressure value. In addition, with the aging of the population, there is a great demand for accuracy and reliability in blood pressure measurement when considering prevention of circulatory diseases and metapolitic syndromes in which hypertension is greatly involved.

Conventionally, blood pressure is measured by wrapping a cuff around a blood pressure measurement site and gradually changing the cuff pressure from a pressure higher than systolic blood pressure (also called systolic blood pressure) to a pressure lower than diastolic blood pressure (also called diastolic blood pressure). as measure of invasive blood圧径detects a change in the auscultatory method and a pressure pulse wave superposed on the internal pressure of the air bag of the microphone method and a cuff for measuring blood pressure by detecting Similarly Korotkoff sounds blood pressure The oscillometric method is used to measure.

Furthermore, Patent Document 1 discloses an improved double cuff method in which the measurement accuracy is further improved by installing a pulse wave detection cuff from the central portion of the ischemic air bag to the distal side in the oscillometric method. Patent Document 2 includes a first axis whose variable is the cuff compression strength and a second axis whose variable is the amplitude of the cuff pulse wave in order to determine the reliability of the measured blood pressure value. A technique for displaying a two-dimensional graph is disclosed.
JP 2000-79101 A Japanese Patent Publication No. 2-25610

  The detection sensitivity of the Korotkoff sound in the above-mentioned microphon method and the specific blood pressure value deriving method in the oscillometric method are different for each sphygmomanometer manufacturer, and are not disclosed. In other words, the accuracy of the measured systolic and diastolic blood pressure values is only published in a few cases based on the accuracy comparison guidelines with EC or auscultation methods in the United States. It is generally not clear on what basis the systolic blood pressure and the diastolic blood pressure were determined in the blood pressure values displayed for the individual measurements.

  In addition, as described above, the microphon method is used to statistically analyze the changes in Korotkoff sound, the oscillometric method is used to change the pressure pulse wave, and the correlation with the systolic blood pressure and diastolic blood pressure points obtained by the auscultation method. It is used as a blood pressure measurement method. Therefore, the method is not a method that takes into account the living body and physiological variations of the individual of the measurer. Therefore, if a change profile of the pulse wave amplitude value deviating from a general statistical distribution is obtained due to a difference in blood vessel extensibility among individuals or the presence of arrhythmia, a correct blood pressure value may not be derived.

  However, the user has not been able to confirm on what basis the individual measurement values (blood pressure values) derived by the blood pressure measurement device are determined. For example, it is possible to determine whether or not a large artifact (noise due to body movement) is mixed by using the technique described in Patent Document 2 described above, but since the measurement algorithm is not disclosed, the blood pressure value is not disclosed. It is not possible to determine how it affects the decision. For example, it is not possible to sufficiently judge the degree of influence such as fluctuation of cuff pulse wave due to breathing by the presenter. In other words, the user cannot determine how much noise affects the blood pressure value. For this reason, when the measured blood pressure value is doubtful, it is necessary to perform blood pressure measurement a plurality of times or to perform measurement using a doctor's auscultation method.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a user with a technique capable of determining the reliability of each derived measurement value and deriving a more accurate blood pressure value. To do.

In order to solve the above-described problems, the blood pressure measurement device of the present invention has the following configuration. That is,
A cuff to compress the blood pressure measurement site;
Pressure control means for pressurizing or depressurizing the inside of the cuff;
A pressure sensor for detecting the pressure in the cuff, and a blood pressure measurement device capable of detecting the pressure in the cuff in a decompression process in which a plurality of pulse wave components are superimposed in time series,
For each of the plurality of pulse wave components superimposed on the pressure in the cuff, after detecting the maximum gradient point between the peak point and the bottom point appearing prior to the peak point, at the detected maximum gradient point Deriving means for deriving a displacement between the pressure value and the pressure value at the bottom point appearing prior to the maximum slope point;
Of the displacements derived from each of the plurality of pulse wave components, based on the magnitude of the change when comparing each displacement derived from adjacent pulse wave components, to determine the systolic blood pressure value, Blood pressure value determining means for determining a diastolic blood pressure value based on a comparison between the displacement derived from each of the plurality of pulse wave components and a predetermined threshold ;
On the two-dimensional graph in which the pressure in the cuff is set on the first axis and the value corresponding to the displacement is set on the second axis, the displacement corresponding to the pressure in the cuff in the decompression process is time-sequentially. Display means for plotting and displaying a line graph ,
The display means further displays, on the first axis of the two-dimensional graph, an index indicating a systolic blood pressure value determined by the blood pressure value determining means and an index indicating a diastolic blood pressure value, respectively. Features.

The display means sets the pressure in the cuff as a first axis and the pulse wave amplitudes of the plurality of pulse wave components as a third axis for at least a part of the period of the two-dimensional graph. A dimensional graph is also displayed .

The at least part of the period is a period including a time point from when the pressure in the cuff is higher than the systolic blood pressure value to a time point when the pressure in the cuff becomes lower than the diastolic blood pressure value .

In order to solve the above-described problems, a method for controlling a blood pressure measurement device according to the present invention has the following configuration. That is,
  A cuff to compress the blood pressure measurement site;
  Pressure control means for pressurizing or depressurizing the inside of the cuff;
  A pressure sensor for detecting the pressure in the cuff, and a control method of a blood pressure measurement device capable of detecting the pressure in the cuff in a decompression process, wherein a plurality of pulse wave components are superimposed in time series,
  For each of the plurality of pulse wave components superimposed on the pressure in the cuff, after detecting the maximum gradient point between the peak point and the bottom point appearing prior to the peak point, at the detected maximum gradient point A derivation step for deriving a displacement between a pressure value and a pressure value at the bottom point appearing prior to the maximum slope point;
  Of the displacements derived from each of the plurality of pulse wave components, based on the magnitude of the change when comparing each displacement derived from adjacent pulse wave components, to determine the systolic blood pressure value, A blood pressure value determining step for determining a diastolic blood pressure value based on a comparison between the displacement derived from each of the plurality of pulse wave components and a predetermined threshold;
  On the two-dimensional graph in which the pressure in the cuff is set on the first axis and the value corresponding to the displacement is set on the second axis, the displacement corresponding to the pressure in the cuff in the decompression process is time-sequentially. Plotting and displaying a line graph, and
  In the display step, an index indicating the systolic blood pressure value determined in the blood pressure value determining step and an index indicating the diastolic blood pressure value are further displayed on the first axis of the two-dimensional graph. Features.

  ADVANTAGE OF THE INVENTION According to this invention, the technique which enables judgment of the reliability of each measured value derived | led-out by the blood-pressure measuring apparatus and can derive a more exact blood-pressure value can be provided to a user.

(First embodiment)
The blood pressure measurement device of the present invention will be described with reference to the drawings based on a preferred embodiment. In the following, first, the pulse wave signal obtained by the double cuff method in the process of reducing the cuff pressure will be described in detail, and then the detailed operation of the blood pressure measurement device of the present invention will be described.

<Device configuration>
FIG. 8 is a diagram illustrating a configuration of the blood pressure measurement device according to the first embodiment.

  A large cuff 1 for blood vessel ischemia is connected to a pressurizing pump 3 and a pressure reducing control valve (solenoid valve) 4 through a tube 11. The large cuff 1 is connected to the pressure sensor 5 via the fluid resistance 13. Further, the small cuff 2 for pulse wave detection is located substantially at the center of the large cuff 1, and is connected to the pressure sensor 5 via the tube 12. An outline of blood pressure measurement using these double cuffs is disclosed in Patent Document 1 described in the background art.

  The small cuff 2 for pulse wave detection is provided at the cuff central portion of the large cuff 1 for blood vessel ischemia, and captures the change in the intravascular volume at the cuff central portion best. The fluid resistance 13 is a mechanical filter for attenuating or blocking the pulse wave signal detected from the large cuff 1, whereby the small cuff 2 can accurately grasp the change in the intravascular volume under the cuff. As the pressure sensor 5, a diaphragm type pressure-electrical converter using a semiconductor pressure gauge is used. An output signal (pressure signal) of the pressure sensor 5 is amplified by an amplifier 6, converted into a digital signal by an A / D converter (converter) 8 via a low-pass filter 7, and input to a CPU 9. The low pass filter 7 limits the frequency band of the output signal and cuts unnecessary high frequency noise such as valve control noise. The cut-off frequency is set to 10 to 30 Hz.

  The pressure pump 3 and the pressure reduction control valve (solenoid valve) 4 are controlled by the CPU 9. In particular, the decompression control valve (solenoid valve) 4 is controlled to open and close (PWM control) by a PWM signal (ON / OFF pulse signal) from the CPU 9, and from the complete “closed” to the complete “open”, By changing the duty, the opening orifice area is continuously controlled.

  Further, the CPU 9 periodically takes in the pressure signal (cuff pressure signal) converted into digital form from the A / D converter (converter) 8 and separates the pulse wave signal superimposed on the pressure signal from the cuff pressure signal. A function of determining a systolic blood pressure value and a diastolic blood pressure value from the pulse wave signal and the cuff pressure (signal) is provided. Details of the determination of the systolic blood pressure value and the diastolic blood pressure value will be described later.

  Further, the CPU 9 displays the systolic blood pressure value and the diastolic blood pressure value thus determined on the display LCD 10. In addition, the CPU 9 also has a function of displaying a two-dimensional graph on the LCD 10. Therefore, the LCD 10 is configured by a dot matrix LCD capable of displaying a two-dimensional graph.

<Cuff pressure and pulse signal>
FIG. 1 is a graph showing a state in which a pulse wave signal is superimposed on the cuff pressure in the process of reducing the cuff pressure. This graph shows how the magnitude and shape of the pulse wave signal change as the cuff pressure decreases. FIG. 2 is a diagram showing a change of the pulse wave amplitude value superimposed on the cuff pressure in the process of reducing the cuff pressure together with the change of the cuff pressure. It is shown that in the process of reducing the cuff pressure, the pulse wave amplitude value gradually increases, and after passing through the point M where the maximum amplitude value appears, the pulse wave amplitude value tends to gradually decrease.

  FIG. 3 is a cross-sectional view of the cuff (double cuff) in the longitudinal direction (the direction in which the upper arm extends) of the blood pressure measurement device according to the first embodiment. As described above, the cuff according to the first embodiment is a double cuff composed of a large cuff (first cuff) 1 for blood vessel ischemia and a small cuff (second cuff) 2 for pulse wave detection. FIG. 3 shows a state in which the blood vessel 100 is blocked at the portion Q by the pressurized large blood vessel cuff 1 to suppress the blood flow from the upstream side 100a to the downstream side 100b.

  The force that squeezes the arm with the large cuff 1 is strongest at the center in the width direction of the cuff (part A in FIG. 3, hereinafter simply referred to as the cuff center A), and weakens as it approaches both ends. Then it becomes almost 0. This phenomenon is called the cuff edge effect. The small cuff 2 is provided at the cuff central portion A in the width direction of the cuff, so that the intravascular pressure change (intravascular volume change) at this portion is best captured. In the specification, “cuff pressure” means the pressure in the cuff, but is substantially equal to the compression force of the arm at the cuff central portion A in the cuff width direction. It is also the pressure from the cuff applied to the blood vessel under the cuff center A.

<Characteristics of each component constituting pulse wave signal>
The pulse wave signal superimposed on the cuff pressure detected by the pulse wave detection small cuff 2 is mainly caused by a direct change in the cuff pressure accompanying a change in the intravascular volume due to the blood flow from the upstream side of the cuff. It is divided into a component W1 derived (hereinafter referred to as W1 component) and a component W2 (hereinafter referred to as W2 component) derived from a change in intracuff pressure due to a change in intravascular volume due to reflection from a blood vessel downstream of the cuff. The W1 component is a component W1-A (hereinafter referred to as W1-A component) derived from a pressure change (intravascular volume change) under the central portion of the cuff width direction, that is, the cuff central portion A. A component W1-B (hereinafter referred to as W1-) derived from a pressure change (intravascular volume change) under the upstream portion in the width direction of the cuff, that is, the portion B in FIG. 3 (hereinafter simply referred to as the cuff upstream portion B). B1) and the downstream portion in the width direction of the cuff, that is, the component W1-C (hereinafter referred to as W1) derived from the change in intravascular volume under the portion C in FIG. 3 (hereinafter simply referred to as the cuff downstream portion C). -C component).

  FIG. 5 is a diagram schematically showing each component included in the pulse wave signal PW. Specifically, the pulse wave signal PW indicated by a thick line includes a W1 component and a W2 component, and the W1 component is composed of a W1-A component, a W1-B component, and a W1-C component.

  The pulse wave signal PW is a typical example observed when the cuff pressure is between the systolic blood pressure value and the diastolic blood pressure value in the decompression process. When the cuff pressure in the decompression process is between the systolic blood pressure value and the diastolic blood pressure value, there is a phenomenon in which blood flows into the cuff central portion A and circulates in blood vessels downstream of the cuff. In this case, the W1-A component derived from the change in the intravascular volume under the cuff central portion A accompanying the blood flow to the downstream blood vessel and the change in the intravascular volume under the cuff downstream portion C are obtained. The W1-C component which overlaps with the W1-B component derived from the change in the intravascular volume due to the blood flow flowing under the cuff upstream portion B, forms a W1 component overlapping with a time delay, that is, with a time difference, and further downstream. The pulse wave signal PW in which the W2 component due to reflection from the side overlaps with a time difference and is superimposed on the cuff pressure is formed.

  Here, since the small cuff 2 for pulse wave detection is attached to the cuff central portion A, the W1-A component is most easily detected as compared with the W1-B component and the W1-C component. Therefore, the characteristics of the W1-A component are largely reflected in the shape of the W1 component, compared to the characteristics of the W1-B component and the W1-C component.

  The W1-B component indicates an intravascular volume change under the cuff upstream portion B, but the upstream portion B is located on the upstream side (heart side) compared to the central portion A and the downstream portion C. It appears earlier than the component and the W1-C component, and is reflected in the rising shape of the W1 component. Moreover, about the W1-C component, although the intravascular volume change under the cuff downstream part C is shown, the downstream part C is located downstream of the central part A, and the compression force of the cuff of the downstream part C is the central part A. Therefore, the opening / closing of the blood vessel under the downstream portion C is almost synchronized with the opening / closing of the blood vessel under the central portion A, and the time difference between the appearance of the W1-A component and the W1-C component is substantially Not really.

  Since the W2 component is a reflection from the blood vessel on the downstream side of the cuff with respect to the blood flow from the upstream, the peak appears at the timing when the intravascular pressure on the downstream side becomes higher than the cuff pressure. More late. Generally, the reflection of the pulse wave signal in the shape of the W2 component on the overall shape is smaller than the reflection of the shape of the W1 component (combination of the W1-A component, the W1-B component, and the W1-C component). In addition, when the cuff pressure in the decompression process is close to the diastolic blood pressure value, the intravascular pressure on the downstream side of the cuff has sufficiently recovered to the state before ischemia by the cuff, so reflection from the downstream blood vessel is substantially reduced. It disappears. Therefore, in the pulse wave signal in which the cuff pressure is detected in the vicinity of the diastolic blood pressure value, the W2 component substantially disappears.

  FIG. 6 is a diagram schematically showing how the W1-A component derived from the change in the intravascular volume under the cuff central portion A is generated and changed in the process of reducing the cuff pressure.

  In graph 1, the horizontal axis represents the elapsed time when the cuff pressure is reduced at a constant pressure reduction rate, the vertical axis represents the intravascular external pressure difference (intravascular pressure−cuff pressure), and an open waveform (blood vessel) Based on the case where the internal pressure change is simplified with a triangular waveform, the change in the intravascular external pressure difference under the cuff central portion A derived from the blood pressure waveform (intravascular pressure change) at each time point in the elapsed time (blood pressure waveform) The same triangular waveform).

  Further, on the upper side of the graph 1, the change in the intravascular volume at each time point corresponding to the change in the intravascular external pressure difference is shown as the graph 2 with the vertical axis as the intravascular volume. On the left side of the vertical axis of the intravascular / external pressure difference, the relationship between the intravascular / external pressure difference and the intravascular volume that converts the change in the intravascular external pressure difference (graph 1) into the change in the intravascular volume (graph 2), and the horizontal axis indicates the intravascular volume. Is represented as graph 3.

  Regarding the relationship between the intravascular external pressure difference and the intravascular volume in Graph 3, a simplified relationship is assumed by paying attention to the tendency of the intravascular volume to suddenly change (rapid increase or decrease) near the intravascular external pressure difference of 0. Yes. That is, the change between the state in which the blood vessel is completely closed (intravascular volume 0) and the state in which the blood vessel is completely open (intravascular volume Vmax) in the process of increasing / decreasing the intravascular external pressure difference, the intravascular volume is V0 and V1. This is represented by a broken line consisting of straight lines of a steep portion between V0 and V1 and a gentle slope portion of V0 or less and V1 or more.

  This is a state in which the blood vessel is crushed by its own weight (intravascular volume V0) at a position where the intravascular external pressure difference is 0, but when the intravascular external pressure difference changes to a positive value from this position, the intravascular volume suddenly increases. The blood vessel reaches a sufficiently open state (intravascular volume V1), and then gradually increases (towards the maximum intravascular volume Vmax) with respect to the change in the intravascular external pressure difference, and the intravascular external pressure difference When the position changes from 0 to a negative value, the intravascular volume tends to decrease gradually (towards the intravascular volume 0). In the graph 3, the steep portion between the blood vessel volume V0 and V1 is approximated by a straight line, so the rate of change in the blood vessel volume is the same during this period. The rate of change at the position where the internal / external pressure difference is 0 (the position of the blood vessel volume V0) is the maximum.

  The degree of such a tendency that the intravascular volume suddenly changes (rapidly increases) when the intravascular external pressure difference is close to 0 depends on the degree of extensibility of the blood vessel of the measurement subject. It is thought that it can be made.

  In the graph 1, in the process of reducing the cuff pressure (elapsed time), a is a time point at which the cuff pressure is equal to the systolic blood pressure value, and b is approximately at the center of the systolic blood pressure value and the diastolic blood pressure value. Time point c shows a change (triangular waveform) in the intravascular external pressure difference under the cuff central portion A when the cuff pressure is equal to the diastolic blood pressure value.

  Changes in the intravascular external pressure difference (triangular waveforms) a, b, and c at each time point in the elapsed time (peak points) are portions of the systolic blood pressure value in the open waveform (intravascular pressure change) (i.e., The lower apex (bottom point) is derived from the portion of the diastolic blood pressure value (ie, the early systolic phase of the heart) in the blood pressure waveform (intravascular pressure change). Is.

  The change in the intravascular external pressure difference of a, b, and c in the graph 1 is converted into the change in the intravascular volume using the relationship between the intravascular external pressure difference and the intravascular volume in the graph 3. (B) and (c). In (a), (b), and (c), the initial position of the heart (two positions in the front and rear) is indicated by white circles. This corresponds to the downward apex (bottom point) of the open waveform (change in intravascular pressure). A component (indicated by a thick line) shown between the initial positions of the heart in the systolic period (two places before and after) is the W1-A component. That is, graph 2 shows how the W1-A component changes at each point in the cuff pressure reducing process (elapsed time).

  Among the W1-A components (intravascular volume change) of (b) and (c), the positions where the intravascular external pressure difference becomes 0 preceding the peak point are indicated by dots. In the W1-A component (intravascular volume change) of (a), the peak point corresponds to a position where the intravascular external pressure difference is 0, and this position is indicated by a dot. The position where the intravascular external pressure difference indicated by the dots (a), (b), and (c) is 0 is actually a portion where the intravascular volume rapidly increases (rapidly increases) (the maximum gradient in the first half of the waveform) Point).

  Furthermore, in the W1-A components of (a), (b), and (c), the position where the intravascular volume that occurs behind the peak point is minimized is also indicated by dots. It is known that the position where the intravascular volume that occurs behind the peak point of the W1-A component is minimized is substantially equal to the position of the downward peak point (bottom point) of the actual pulse wave signal. Therefore, hereinafter, the position where the intravascular volume that occurs behind the peak point of the W1-A component is minimized is referred to as the bottom point of the W1-A component.

  In graph 2, the portion where the internal volume of the blood vessel rapidly increases with the W1-A component (the maximum gradient point in the first half of the waveform) [the position where the intravascular external pressure difference indicated by the dot becomes 0] is the heart preceding the W1-A component. The time (time difference) delayed from the initial systolic position is indicated by t1, and the time (time difference) at which the bottom point of the W1-A component advances from the next initial systolic position is indicated by t2. The period is indicated by T. Here, the period T of the pulse wave signal is substantially constant during the measurement period. In addition, the downward displacement from the portion where the intravascular volume at the bottom point of the W1-A component rapidly increases (the maximum gradient point in the first half of the waveform) is indicated by H.

  The sum of the delay time (time difference) t1 and the advance time (time difference) t2 is t. (T = t1 + t2) Considering that t1 and t2 of W1-A components generated continuously are almost the same, t is the leading of the rapidly rising portion (maximum gradient point in the first half) of the W1-A component of interest. This is considered to indicate the time delay (time difference) of the W1-A component from the bottom point, that is, the time difference of appearance of the maximum gradient point from the preceding bottom point (of the W1-A component).

  As shown in graphs (a), (b), and (c), the time difference t1 and the time difference t2 become smaller as the cuff pressure approaches the systolic blood pressure value from the systolic blood pressure value. In other words, the time difference t of the appearance of the maximum gradient point from the preceding bottom point decreases as the cuff pressure approaches the systolic blood pressure value from the systolic blood pressure value. Since the period T of the pulse wave signal is substantially constant during the measurement period, the phase difference 2π (t / T) appearing from the preceding bottom point of the maximum gradient point is also equal to the cuff pressure. It decreases as the systolic blood pressure value approaches the diastolic blood pressure value.

  As shown in (c) of graph 2, when the cuff pressure becomes equal to the diastolic blood pressure value, the preceding bottom point and maximum gradient point of the W1-A component are obtained under this simplified graph. (A sudden rise point) and the early systolic period occur simultaneously, t1 = 0, t2 = 0, and t = 0.

  Furthermore, from (b) and (c) of graph 2, the downward displacement H from the maximum slope point (rapid rise point) of the bottom point of the W1-A component decreases as the cuff pressure approaches the diastolic blood pressure value. Is also shown. As shown in (c), at the time when the cuff pressure becomes equal to the diastolic blood pressure value, the position of the bottom point and the position of the maximum gradient point of the W1-A component are based on this simplified graph. In agreement, H = 0 (displacement disappears).

  From these facts, the following three features can be found for the actual W1-A component.

      The delay (time difference t or phase difference 2π (t / T)) from the bottom point of the steeply rising portion (maximum gradient point) of the W1-A component decreases as the cuff pressure approaches the diastolic blood pressure value.

      The displacement H of the bottom point from the steeply rising portion (maximum gradient point) of the W1-A component decreases as the cuff pressure approaches the diastolic blood pressure value.

      The shape of the W1-A component appears when the cuff pressure becomes smaller than the pressure of the systolic blood pressure value.

<Characteristics of pulse wave signal>
As described above, the pulse wave signal PW is divided into the components, and the simplified examination content about the W1-A component is shown. However, the pulse wave signal PW is actually separated into the W1-A component, the W1-B component, and the like. The pulse waves are detected by the small cuff 2 for pulse wave detection as one pulse wave signal on which the signals are superimposed.

  However, as already described, although the W1-B component is reflected in the rising portion of the W1 component, the W1-A component largely reflects the shape of the W1 component of the pulse wave signal superimposed on the cuff pressure. Further, the W2 component of the pulse wave signal is generally smaller than the W1 component, and the cuff pressure disappears in the vicinity of the diastolic blood pressure value.

  Therefore, the following three characteristics can be found as the characteristics of the detected pulse wave signal.

      The delay (time difference t or phase difference 2π (t / T)) from the bottom point of the steeply rising portion (maximum gradient point) of the pulse wave signal becomes smaller as the cuff pressure approaches the diastolic blood pressure value.

      The displacement H of the bottom point from the steeply rising portion (maximum gradient point) of the pulse wave signal becomes smaller as the cuff pressure approaches the diastolic blood pressure value.

      -The steep rise of the pulse wave signal changes greatly when the cuff pressure falls below the systolic blood pressure value.

  7 (a) and 7 (b) show the pulse in which the cuff pressure was superimposed on the cuff pressure detected at the time point between the systolic blood pressure value and the diastolic blood pressure value, respectively. It is a figure which shows a wave signal.

  Each pulse wave signal shows a steeply rising portion (maximum gradient point) Um in the first half, and a peak point Pe and two bottom points B1 and B2 that occur before or after the peak point Pe. Furthermore, the figure shows the time difference t from the bottom point B1 of the maximum gradient point Um, the period T, and the downward displacement H of the bottom point B2 from the maximum gradient point (rapidly rising point) Um. Note that the bottom point B1 is also a bottom point B2 generated behind the peak point of the pulse wave signal generated in advance, and the pulse wave signals generated continuously have almost the same shape. The displacement of the point B2 from the maximum gradient point (abrupt increase point) Um is almost the same as the displacement of the bottom point B1 from the maximum gradient point (abrupt increase point) Um.

  As described above, at the time of the diastolic blood pressure value, the time difference t (phase difference 2π (t / T)) and the displacement H are smaller than those between the systolic blood pressure value and the diastolic blood pressure value. You can see the situation.

  The W1-A component reflects the shape of the W1 component of the pulse wave signal superimposed on the cuff pressure more than the W1-B component. This is because the position where the steep rising portion (maximum gradient point) Um appears changes from the portion where the W1-B component is reflected when the W1-A component appears to the position where the W1-A component appears. It turns out that. Since the W1-A component appears only after the systolic blood pressure value becomes lower than the systolic blood pressure value, the steeply rising portion (maximum slope point) Um is derived from the shape when the pressure higher than the systolic blood pressure value is applied to the cuff. The blood pressure value below the blood pressure value is seen to change greatly.

<Determination of blood pressure value>
Therefore, based on the characteristics of the pulse wave signal described above, the CPU 9 which is a blood pressure value determining unit can determine the blood pressure value as follows.

      The CPU 9 sets the cuff pressure at the time when the phase difference between the appearance of the bottom point and the maximum gradient point (rapid rise point) that occurs before the peak point of the pulse wave signal becomes smaller than a predetermined threshold value as the diastolic blood pressure value (dilation) Determination of blood pressure value in period 1).

      The CPU 9 uses the cuff pressure when the displacement (difference in amplitude value) from the maximum gradient point (abrupt ascending point) of the bottom point that occurs before or after the peak point of the pulse wave signal becomes smaller than a predetermined threshold value as the diastolic blood pressure. Value (diastolic blood pressure value determination 2).

      ・ Check the phase difference value of the appearance of the bottom point and the maximum gradient point (sudden rising point) that precedes the peak point of the pulse wave signal in order from the pulse wave signal with the lowest cuff pressure, and there is no value continuity The CPU 9 sets the cuff pressure value at the point indicating the change as the systolic blood pressure value (systolic blood pressure value determination 1).

      ・ Check the displacement (difference in amplitude value) from the maximum slope point (abrupt rise point) of the bottom point that occurs before or after the peak point of the pulse wave signal in order from the pulse wave signal with the lowest cuff pressure. The CPU 9 sets the cuff pressure value at the point showing a large change without continuity as the systolic blood pressure value (systolic blood pressure value determination 2).

  As described above, the bottom point and the maximum gradient point (rapidly rising point) of the pulse wave signal are detected in the individual pulse wave signals. The predetermined threshold is set in consideration of noise or the like in the signal processing process of the detected pulse wave. Note that the influence of measurement conditions such as individual differences and decompression speed on noise and the like in this signal processing process is generally small.

  These blood pressure determination methods are set based on parameters (statistical methods) that are greatly influenced by individual differences in measurement subjects and measurement conditions (decompression speed, etc.), as in a conventional oscillometric sphygmomanometer. It is not necessary to handle the change profile of the pulse wave amplitude value during the cuff pressure reduction process using the ratio of the pulse wave amplitude value to the maximum pulse wave amplitude value. Therefore, measurement with small variations due to individual differences and measurement conditions (decompression speed, etc.) can be realized.

<Operation of the device>
FIG. 9 is a flowchart showing a schematic operation of the blood pressure measurement device according to the first embodiment.

  When the measurement start SW (switch) of the electronic sphygmomanometer is turned on (step S1), the pressure reduction control valve 4 is completely closed (step S2), and the drive of the pressurization pump 3 is started (ON) by the control of the CPU 9 (Step S3).

  When the pressurizing pump 3 is driven, reading of the cuff pressure is started (step S4), and it is determined whether or not the read cuff pressure has reached a pressure value (set pressure) sufficiently higher than a preset systolic blood pressure value. (Step S5). The pressurization pump is driven until the cuff pressure reaches the set pressure, and when the cuff pressure reaches the set pressure, the drive of the pressurization pump 3 is stopped (OFF) (step S6).

  After that, by controlling the CPU 9 of the decompression control valve 4 to start the slow exhaust, the slow decompression is started at a predetermined decompression speed (for example, 2 to 3 mmHg / second) (step S7). During this decompression process, the CPU 9 sequentially reads the cuff pressure every predetermined time interval (sampling time) (step S8), and extracts the pulse wave signal superimposed on the cuff pressure (step S9).

  Then, based on the pulse wave signal extracted in step S9, the value of the phase difference (t / T) of the pulse wave is sequentially derived for each pulse wave period in descending order of the corresponding cuff pressure. Then, a point where the value of the phase difference is smaller than a predetermined threshold is searched, and the cuff pressure value corresponding to the detected point is determined as the diastolic blood pressure value (step S10). Thereafter, the acquired pulse wave signal is searched for a point where the value of the phase difference greatly changes in order from the lowest corresponding cuff pressure, and the cuff pressure value corresponding to the detected point is determined as the systolic blood pressure value ( Step S11). The flowchart for determining the systolic blood pressure value and the diastolic blood pressure value will be described later.

  After the determination of each blood pressure value, the decompression control valve is fully opened (completely “open”) to return the cuff pressure to atmospheric pressure (step S12). Then, the stored systolic blood pressure value and diastolic blood pressure value are displayed on the LCD 10 under the control of the CPU 9 (step S13). As will be described later, the LCD 10 also displays a graph as a basis for determining the blood pressure.

  FIG. 10 is a detailed flowchart of the determination of the diastolic blood pressure value and the systolic blood pressure value.

  The cuff pressure P is detected at predetermined time intervals (every sampling time) even after the systolic blood pressure value is determined (step S100), and the pulse wave signal superimposed on the cuff pressure (see FIG. 7) is detected. Extract (step S101). From the pulse wave signal, the continuous bottom points B1 and B2 and the peak point Pe between them are detected (step S102, step S103, step S104), and the bottom point B1 (the bottom point generated prior to the peak point) A point having the maximum gradient (maximum gradient point) Um is detected between the peak points Pe, that is, in the first half of the pulse wave signal (step S105). Then, the time difference t between the appearance of the bottom point B1 and the point having the maximum gradient (maximum gradient point) Um is calculated (step S106). A time interval T between appearances of the bottom point B1 and the bottom point B2 is obtained (step S107), and a phase difference (t / T) is calculated (step S108). Here, since the bottom point B2 becomes the bottom point B1 of the next pulse wave signal, the time interval T is also a pulse wave interval and is also a pulse period.

  When the phase difference (t / T) is calculated for each pulse wave signal of one cycle, the cuff pressure in the horizontal axis (X axis) direction and the phase difference (t / T in the vertical axis (Y axis) direction are calculated. Each measurement point is plotted on the two-dimensional graph obtained by T). Details of the display will be described later.

  When this phase difference (t / T) becomes smaller than a predetermined threshold k, the cuff pressure P at that time is determined as a diastolic blood pressure value (step S110). When the phase difference (t / T) is equal to or greater than the predetermined threshold k, the same processing is sequentially performed on the next pulse wave signal superimposed on the further reduced cuff pressure to determine the diastolic blood pressure value. is there.

  After the diastolic blood pressure value is determined, the change (difference) in the phase difference is sequentially checked in order from the pulse wave signal from the lower corresponding cuff pressure (steps S111 and S112). When a point where the change in phase difference changes greatly is found, the cuff pressure P corresponding to the point is determined as the systolic blood pressure value (step S113).

  Here, the combination of (diastolic blood pressure value determination 1) and (systolic blood pressure value determination 1) shown in <Determination of blood pressure value> has been described as an example. However, it may be executed based on other combinations of methods for determining the diastolic blood pressure value and the systolic blood pressure value. In particular, by using a combination of a plurality of determination methods for each of the diastolic blood pressure value and the systolic blood pressure value, it is possible to derive a blood pressure value with higher accuracy.

<Example of screen display>
As described above, the LCD 10 also displays a graph as a basis for determining the blood pressure. FIG. 11 is a diagram illustrating an example of a graph display displayed on the LCD. FIG. 11A is a diagram illustrating a two-dimensional graph in which the cuff pressure is taken in the horizontal axis (X-axis) direction and the phase difference (t / T) is taken in the vertical axis (Y-axis) direction. This figure shows an example in which the systolic blood pressure value is 110 mmHg and the diastolic blood pressure value is 70 mmHg.

  By performing such display, the user can easily determine the reliability of the blood pressure value displayed in step S13. That is, in the displayed two-dimensional graph, it can be easily determined by the clarity of the phase difference change at the cuff pressure portion corresponding to the blood pressure value displayed in step S13.

  FIG. 11B is a diagram showing a two-dimensional graph in which the pulse amplitude is taken in the vertical axis (Y-axis) direction together with the display of FIG. With such a display, it is possible to easily determine whether or not noise or the like due to a large body movement is mixed.

  Here, two time series (phase difference and pulse wave amplitude) are displayed so as to be superimposed by a line graph and a bar graph, respectively, but any display method can be used as long as the display format is easy to compare. Is available. Further, as is obvious from the determination method shown in <Determination of blood pressure value>, a displacement (pressure value difference) may be displayed instead of the phase difference.

  As described above, according to the blood pressure measurement device according to the first embodiment, the blood pressure value (systolic blood pressure value and diastole) is not based on a statistical method but based on a change in the shape of the pulse wave signal (one-period pulse wave signal). Blood pressure). In addition, the time series data used for blood pressure measurement is displayed on the LCD screen so that the user can confirm. By configuring in this way, the user can objectively determine whether or not the derived blood pressure value is appropriate.

  Therefore, it is possible to improve the objectivity, satisfaction, and reliability of blood pressure measurement. Also, by displaying the amplitude of the Korotkoff sound detected during the measurement or the pressure difference from the bottom of the pressure pulse wave to the maximum change point, the degree of arrhythmia, the degree of artifact due to body movement, etc. You can also get information about differences in size due to solids. Therefore, it becomes possible to inform the measurer of more information than the blood pressure monitor that displays only the conventional numerical values. As a result, it is possible to provide measurement reliability information by providing information that is the basis for the measured blood pressure value. Therefore, the necessity of re-measurement can be understood, and a highly reliable blood pressure value can be provided. In addition, patient information related to treatment such as arrhythmia and blood pressure fluctuation can be provided, which is useful for treatment.

(Modification 1)
Here, an example of a blood pressure measurement device using a triple cuff method, which is a further improvement of the double cuff method, will be described. Note that the device configuration and the operation of the device other than the cuff are the same as those in the first embodiment, and a description thereof will be omitted. Below, the effect by using a triple cuff is mainly demonstrated.

<Cuff pressure and pulse signal>
FIG. 4 is a longitudinal sectional view of a cuff (triple cuff) of the blood pressure measurement device according to the second embodiment. The cuff according to the modification is a triple cuff including a large cuff 1 for blood vessel ischemia, a small cuff 2 for pulse wave detection, and a sub-cuff 3 provided in the upstream portion. It is shown that the blood vessel 100 is blocked at the portion Q by the pressurized large cuff 1 and subcuff 3 for blood vessel ischemia, and the blood flow from the upstream side 100a to the downstream side 100b is suppressed. However, compared with the case of the double cuff (FIG. 3), the case of the triple cuff (FIG. 4) is different in that the invasion of blood flow in the section indicated by “B” is prevented by the effect of the sub-cuff 3.

  As described in the first embodiment, the pulse wave signal superimposed on the cuff pressure detected by the small cuff 2 for detecting the pulse wave is a direct pressure change associated with the blood flow from the upstream side of the cuff ( It is divided into a component W1 (hereinafter referred to as W1 component) derived from the change in volume in the blood vessel (hereinafter referred to as W1 component) and a component W2 (hereinafter referred to as W2 component) derived from the pressure change (intravascular volume change) due to reflection from the blood vessel downstream of the cuff. It is done. The W1 component can be divided into three components W1-A, W1-B, and W1-C.

  The sub-cuff 3 has an effect of suppressing the W1-B component derived from the change in the intravascular volume due to the blood flow flowing under the cuff upstream portion B by compensating the cuff edge effect of the large cuff 1. FIG. 12 is a diagram illustrating a pulse wave signal of one cycle acquired by a double cuff and a triple cuff. 12A corresponds to a double cuff, and FIG. 12B corresponds to a triple cuff. As can be seen from FIG. 12, in the pulse wave signal acquired by the triple cuff, it can be seen that the W1-A component is captured more clearly as a result of the W1-B component being greatly reduced. Therefore, it will be understood that the W1-A component that is most important in determining the blood pressure value can be understood more clearly. As a result of blue, the “phase difference” or “displacement (pressure value)” used to determine the blood pressure value can be derived more accurately.

  As described above, according to the blood pressure measurement device according to the modification, it is possible to accurately acquire a pulse wave signal important for blood pressure determination. As a result, more accurate blood pressure values (systolic blood pressure values and diastolic blood pressure values) can be derived. In addition, it is possible to provide the user with more accurate data indicating whether or not the derived blood pressure value is appropriate.

(Other embodiments)
<Example of screen display in microphone method>
FIG. 13 is a diagram illustrating an example of a graph display displayed on the LCD. FIG. 13 is a diagram showing a two-dimensional graph in which the cuff pressure is taken in the horizontal axis (X axis) direction and the intensity of the Korotkoff sound (K sound) is taken in the vertical axis (Y axis) direction. Further, the change in the cuff pressure corresponding to the time series of the intensity of the Korotkoff sound (K sound) is also shown in the upper part of the drawing. This figure shows an example in which the systolic blood pressure value is 160 mmHg and the diastolic blood pressure value is 80 mmHg. Then, an indicator (Δ) is displayed at a position corresponding to the determined blood pressure value (systolic blood pressure value (SYS), diastolic blood pressure value (DIA)).

In the microphone method, a blood pressure value is generally determined based on threshold values (TH _SYS , TH _DIA ) designated in advance. Therefore, you may display the said threshold value together in a two-dimensional graph.

  By performing such display, the user can easily determine what data the blood pressure value is determined based on.

<Example of screen display in oscillometric method>
FIG. 14 is a diagram illustrating an example of a graph display displayed on the LCD. FIG. 14 is a diagram showing a two-dimensional graph in which the cuff pressure is taken in the horizontal axis (X axis) direction and the pulse wave amplitude is taken in the vertical axis (Y axis) direction. Further, the change in the cuff pressure corresponding to the time series of the pulse wave amplitude is also shown in the upper part of the drawing. This figure shows an example in which the systolic blood pressure value is 160 mmHg and the diastolic blood pressure value is 80 mmHg. Then, an indicator (Δ) is displayed at a position corresponding to the determined blood pressure value (systolic blood pressure value (SYS), diastolic blood pressure value (DIA)).

In a general oscillometric method, a blood pressure value is determined based on a predetermined threshold (TH _SYS , TH _DIA ). Therefore, you may display the said threshold value together in a two-dimensional graph.

  By performing such display, the user can easily determine what data the blood pressure value is determined based on.

It is a figure which shows a mode that the pulse-wave signal is superimposed on the cuff pressure in the pressure reduction process of the cuff pressure. It is the figure which showed the mode of the change of the pulse wave amplitude value superimposed on a cuff pressure in the pressure reduction process of a cuff pressure with the change of the cuff pressure. It is sectional drawing of the longitudinal direction of the cuff (double cuff) of the blood pressure measuring device which concerns on 1st Embodiment. It is sectional drawing of the longitudinal direction of the cuff (triple cuff) of the blood-pressure measuring device which concerns on a modification. It is a figure which shows typically each component contained in the pulse-wave signal PW (in the case of a double cuff). It is a figure which shows typically a W1-A component originating in the blood vessel volume change under the cuff center part A arising in the pressure reduction process of a cuff pressure, and changing. It is a figure which shows the pulse wave signal superimposed on the cuff pressure detected when the cuff pressure is between the systolic blood pressure value and the diastolic blood pressure value and at the time of the diastolic blood pressure value. It is a figure showing composition of a blood pressure measuring device concerning a 1st embodiment. It is a flowchart which shows schematic operation | movement of the blood-pressure measurement apparatus which concerns on 1st Embodiment. It is a detailed flowchart of determination of a diastolic blood pressure value and a systolic blood pressure value. It is a figure which shows an example of the graph display displayed on LCD. It is a figure which shows the pulse wave signal of 1 period acquired by a double cuff and a triple cuff. It is a figure which shows the other example of the graph display displayed on LCD (microphone method). It is a figure which shows the further another example of the graph display displayed on LCD (oscillometric method).

Claims (6)

A cuff to compress the blood pressure measurement site;
Pressure control means for pressurizing or depressurizing the inside of the cuff;
A pressure sensor for detecting the pressure in the cuff, and a blood pressure measurement device capable of detecting the pressure in the cuff in a decompression process in which a plurality of pulse wave components are superimposed in time series,
For each of the plurality of pulse wave components superimposed on the pressure in the cuff, after detecting the maximum gradient point between the peak point and the bottom point appearing prior to the peak point, at the detected maximum gradient point Deriving means for deriving a displacement between the pressure value and the pressure value at the bottom point appearing prior to the maximum slope point;
Of the displacements derived from each of the plurality of pulse wave components, based on the magnitude of the change when comparing each displacement derived from adjacent pulse wave components, to determine the systolic blood pressure value, Blood pressure value determining means for determining a diastolic blood pressure value based on a comparison between the displacement derived from each of the plurality of pulse wave components and a predetermined threshold ;
On the two-dimensional graph in which the pressure in the cuff is set on the first axis and the value corresponding to the displacement is set on the second axis, the displacement corresponding to the pressure in the cuff in the decompression process is time-sequentially. Display means for plotting and displaying a line graph ,
The display means further displays, on the first axis of the two-dimensional graph, an index indicating a systolic blood pressure value determined by the blood pressure value determining means and an index indicating a diastolic blood pressure value, respectively. A blood pressure measuring device. The display means, to at least a portion of the period of the two-dimensional graph, the pressure within the cuff to a first axis, and sets the pulse wave amplitude of the plurality of pulse wave component to the third axis 2 The blood pressure measurement apparatus according to claim 1 , wherein a dimensional graph is also displayed. Wherein at least a portion of the period, the blood pressure measuring device according to claim 2, wherein the pressure in the cuff is a period up to and including the time be lower than the diastolic blood pressure value from a higher point than the systolic blood pressure value . The blood pressure measurement device according to any one of claims 1 to 3 , wherein the cuff includes a large cuff for blood vessel ischemia and a small cuff for pulse wave detection connected via a fluid resistance. . The deriving means further includes:
  For each of the plurality of pulse wave components superimposed on the pressure in the cuff, after detecting the maximum gradient point between the peak point and the bottom point appearing prior to the peak point, the detected maximum gradient point and It is possible to derive a value corresponding to the time difference between the bottom point appearing prior to the maximum slope point;
  The blood pressure value determining means further includes:
  Based on the magnitude of change when comparing values corresponding to respective time differences derived from adjacent pulse wave components among values corresponding to the time differences derived from each of the plurality of pulse wave components, It is possible to determine a systolic blood pressure value and determine a diastolic blood pressure value based on a comparison between a value corresponding to the time difference derived from each of the plurality of pulse wave components and a predetermined threshold value,
  The systolic blood pressure value is determined based on either the magnitude of change when comparing the displacements or the magnitude of change when comparing values corresponding to the time difference,
  The diastolic blood pressure value is determined based on either a comparison between the displacement and a predetermined threshold value, or a comparison between a value corresponding to the time difference and a predetermined threshold value. 5. The blood pressure measurement device according to any one of items 4 to 4. A cuff to compress the blood pressure measurement site;
Pressure control means for pressurizing or depressurizing the inside of the cuff;
A pressure sensor for detecting the pressure in the cuff, and a control method of a blood pressure measurement device capable of detecting the pressure in the cuff in a decompression process, wherein a plurality of pulse wave components are superimposed in time series ,
For each of the plurality of pulse wave components superimposed on the pressure in the cuff, after detecting the maximum gradient point between the peak point and the bottom point appearing prior to the peak point, at the detected maximum gradient point A derivation step for deriving a displacement between a pressure value and a pressure value at the bottom point appearing prior to the maximum slope point;
Of the displacements derived from each of the plurality of pulse wave components, based on the magnitude of the change when comparing each displacement derived from adjacent pulse wave components, to determine the systolic blood pressure value, A blood pressure value determining step for determining a diastolic blood pressure value based on a comparison between the displacement derived from each of the plurality of pulse wave components and a predetermined threshold ;
On the two-dimensional graph in which the pressure in the cuff is set on the first axis and the value corresponding to the displacement is set on the second axis, the displacement corresponding to the pressure in the cuff in the decompression process is time-sequentially. Plotting and displaying a line graph , and
In the display step, an index indicating the systolic blood pressure value determined in the blood pressure value determining step and an index indicating the diastolic blood pressure value are further displayed on the first axis of the two-dimensional graph. A control method for a blood pressure measurement device.

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