JP2003093358A - Electronic tonometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the electronic tonometer which can accurately determine the lowest blood pressure without causing variations due to the individual difference and measurement condition of a subject. SOLUTION: In this electronic tonometer, the biggest gradient point is detected between the bottom point of pulse wave elements that overlap the cuff pressure and a peak point where the cuff pressure level at the time when the pulse wave element is detected is determined as the lowest blood pressure when the phase difference t/T (the difference of time: t) that appears from the bottom point of the biggest gradient point becomes smaller than the specified threshold. Thus, the lowest blood pressure can be determined without using a variation profile of a swing range of pulse waves which are notably influenced by the individual difference and measurement condition of the subject.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillometric sphygmomanometer for measuring a minimum blood pressure value based on a pulse wave component superimposed on a cuff pressure.

[0002]

2. Description of the Related Art A blood pressure value (maximum blood pressure value, minimum blood pressure value) of an oscillometric sphygmomanometer is determined by a change in intravascular volume of an artery under a cuff (cuff pressure signal from the cuff).
It is based on the idea that it appears in the pulse wave component superposed on. The method of determining the blood pressure value based on the pulse wave component superimposed on the cuff pressure is usually called an oscillometric method as opposed to the Korotkoff sound method of determining the blood pressure value based on the Korotkoff sound. .

A conventional oscillometric sphygmomanometer (a sphygmomanometer for measuring blood pressure by the oscillometric method) pressurizes the cuff wrapped around the ischemic site to a value higher than the maximum blood pressure value, and then slowly increases the cuff pressure (for example, (2 to 3 mmHg / sec), decompressing to near atmospheric pressure, extracting the pulse wave component superimposed on the cuff pressure during this decompression process, paying attention to the amplitude value of the pulse wave component (pulse wave amplitude value), The systolic blood pressure value and the diastolic blood pressure value are generally determined from the change in the amplitude value (the change profile of the pulse wave amplitude value with respect to the change in the cuff pressure).

FIG. 1 is a graph showing a state in which a pulse wave component is superimposed on the cuff pressure in the process of reducing the cuff pressure. This graph shows that the magnitude and shape of the pulse wave component change as the cuff pressure decreases.

FIG. 2 is a diagram showing how the pulse wave amplitude value superimposed on the cuff pressure changes during the process of decreasing the cuff pressure, together with the change in the cuff pressure. It is shown that the pulse wave amplitude value gradually increases during the depressurization process of the cuff pressure, and after the point M at which the maximum amplitude value appears, the pulse wave amplitude value tends to gradually decrease.

The measurement of the minimum blood pressure value by the conventional oscillometric sphygmomanometer is performed by measuring the maximum pulse wave amplitude in the process of decreasing the pulse wave amplitude value after the point at which the maximum pulse wave amplitude value is detected in FIG. The pulse wave amplitude value closest to the value obtained by multiplying the value by a predetermined rate (for example, 60%) is searched, and the value of the cuff pressure in the vicinity when this pulse wave occurs is determined as the minimum blood pressure value. . That is, the maximum pulse wave amplitude value P at the point M
After the point A is detected, a predetermined ratio is set to α after the point M has elapsed.
(For example, α = 0.6), the pulse wave amplitude value is TH = α
The cuff pressure at the point N closest to × PA is determined as the minimum blood pressure value. Regarding such a method of determining the minimum blood pressure value, in order to minimize the measurement error in each measurement as much as possible, the value of α which is a predetermined ratio is statistically measured by the data of hundreds of people. Improvements such as decisions have also been attempted.

However, the conventional method for determining the minimum blood pressure value by the change profile of the pulse wave amplitude value of the oscillometric blood pressure monitor has the following problems.

First of all, the state of reflection of the change in intravascular pressure of the artery under the cuff on the change in intravascular volume is different in each measurement.

In the case of a subject having a blood vessel with low extensibility due to arteriosclerosis or the like, when the arterial intravascular pressure (hereinafter, simply referred to as intravascular pressure in this specification) exceeds the cuff pressure, the arterial intravascular volume ( Hereinafter, in the present specification, simply referred to as the intravascular volume) undergoes a fairly sharp change (rapid increase), while
In the case of a subject having a highly extensible blood vessel such as a child or a young person, even if the intravascular pressure exceeds the cuff pressure, it does not change as sharply as in the former case. Therefore, the change profile of the pulse wave amplitude value of the subject whose blood vessel extensibility is small increases abruptly after the cuff pressure exceeds the systolic blood pressure value, and suddenly decreases after the diastolic blood pressure value. There is little change between the highest and lowest blood pressure values. On the other hand, the change profile of the pulse wave amplitude value in the case of a subject with large vascular extensibility is:
It exhibits a smooth change overall.

Therefore, as in the conventional oscillometric sphygmomanometer, in the method of searching the pulse wave amplitude value closest to the value obtained by multiplying the maximum pulse wave amplitude value by a predetermined ratio, the minimum blood pressure value is determined. However, it is difficult to measure the diastolic blood pressure value with the same accuracy for the measurement subjects whose pulse wave amplitude value change tendencies are different in the vicinity of the diastolic blood pressure value.

Second, the element of intravascular pressure under the cuff is
The pressure due to the reflection of blood from the downstream side (peripheral side) is included as well as the pressure associated with the pumping of blood flow from the upstream side (heart side) of the cuff.
It depends on the individual measurement.

The venous blood vessel below the cuff has a cuff pressure of about 30 mm.
When it exceeds Hg, it is closed, so the blood pumped out during the decompression process during measurement is pulled down to the blood vessel downstream of the cuff,
The blood pressure in the arterial blood vessel on the downstream side gradually increases so as to recover (approach) to the state before the ischemia by the cuff. When the cuff pressure during the decompression process is near the midpoint between the systolic blood pressure value and the diastolic blood pressure value (around where the pulse wave component of the maximum pulse wave amplitude value is obtained), a transient phenomenon may occur due to the recovery status of the intravascular pressure on the downstream side. As a result, a phenomenon occurs in which the intravascular pressure on the downstream side becomes higher than the cuff pressure at a certain timing of the pulsation cycle, and the pressure change due to the pumping of blood flow from the upstream side is reflected. Then, this reflected pressure change overlaps with the pressure change accompanying the discharge of blood flow from the upstream side under the cuff, and under the cuff, the intravascular pressure change affected by the reflection appears. For this reason, the influence of reflection also appears on the amplitude value of the pulse wave component detected under the cuff. The influence of reflection on the amplitude value of the detected pulse wave component is the timing when the intravascular pressure on the downstream side becomes higher than the cuff pressure and the intravascular pressure change that does not depend on the reflection below the cuff (the blood flow from the upstream side It depends on the phase difference of the timing (the direct pressure change due to the stroke) becomes maximum (a peak occurs in the waveform of the pressure change in the blood vessel). That is, in the depressurization process,
The point at which the phase difference becomes 0 (the depressurization process Position in elapsed time)
The amplitude value of the pulse wave component is most affected by reflection.

The points most affected by this reflex are the blood vessel extensibility of the subject, blood pressure (maximum blood pressure value, minimum blood pressure value), pulse rate, etc. Determined by the speed of pressure recovery.

Focusing on the maximum pulse wave amplitude value, the point at which the pulse wave component having the maximum pulse wave amplitude value appears in the decompression process is
The maximum pulse wave amplitude value is most influenced by reflection when the above-mentioned two timings coincide with the point where the phase difference is 0 (the point most affected by reflection). And, in general, the influence of the reflection that the maximum pulse wave amplitude value receives is the positional relationship between the point where the pulse wave component having the maximum pulse wave amplitude value appears and the point that is most affected by the reflection of the intravascular pressure on the downstream side. Dependent. In this way, the influence of reflexes on the maximum pulse wave amplitude value depends on the point most influenced by reflexes, which is determined by the speed of recovery of intravascular pressure on the downstream side. It depends on

When the cuff pressure is close to the minimum blood pressure value, the intravascular pressure on the downstream side of the cuff has sufficiently recovered to the state before the ischemia by the cuff, so that the intravascular pressure on the downstream side is reflected. The effect of is virtually eliminated.

Thus, the maximum pulse wave amplitude value is affected by different reflections depending on the speed of recovery of intravascular pressure downstream of the cuff, while the pulse wave amplitude value at the point of diastolic blood pressure is A method for determining the diastolic blood pressure value by searching for the pulse wave amplitude value that is closest to the value obtained by multiplying the maximum pulse wave amplitude value by a predetermined ratio, as in the conventional oscillometric sphygmomanometer, because it is not affected by reflection. Then, it is difficult to always obtain the correct minimum blood pressure value.

Thirdly, the elasticity (compliance) characteristic of the cuff is involved in the detection of a change in the intravascular volume under the cuff as a pulse wave component. This characteristic shows that the cuff pressure is near the minimum blood pressure value. When they are different in each measurement.

When the cuff pressure is lower than when the cuff pressure is high, the change in the intracuff pressure with respect to the change in the intravascular volume under the cuff becomes small. Especially, the cuff pressure is about 50 mmH
When it is less than or equal to g, the change in the pressure in the cuff with respect to the change in the intravascular volume sharply decreases.

Therefore, in the case of the subject having a low systolic blood pressure value, the pulse wave amplitude value when the cuff pressure becomes close to the diastolic blood pressure value, as compared with the case of the subject having a high diastolic blood pressure value. Is a pulse wave amplitude value that is measured relatively small with respect to the maximum pulse wave amplitude value and is the closest to the value obtained by multiplying the maximum pulse wave amplitude value by a predetermined ratio, as in the conventional oscillometric sphygmomanometer. It is difficult to obtain the correct minimum blood pressure value by the method of determining the minimum blood pressure value.

2A and 2B respectively show FIG.
The pulse wave component near the point M at which the maximum pulse wave amplitude value appears and the pulse wave component detected near the point N at which the minimum blood pressure value of the subject having a low minimum blood pressure value is detected are schematically illustrated. Illustrated.

As shown in FIG. 3A, the pulse wave component P detected near the point where the maximum pulse wave amplitude value is obtained.
W is a waveform component W1 derived from a direct pressure change (intravascular volume change) associated with blood ejection on the upstream side of the cuff and a pressure change (intravascular volume) due to reflection from a blood vessel on the peripheral (downstream) side of the cuff. (Change)) is detected as a combination of the waveform components W2. Here, since the detected pulse wave amplitude value has the waveform component W2 derived from the pressure change (intravascular volume change) due to reflection, the direct pressure change accompanying the ejection of blood from the upstream side under the cuff. It is larger than the case of only the waveform component W1 derived from (change in intravascular volume).

As shown in FIG. 3 (b), the pulse wave component PW detected near the point where the diastolic blood pressure value of the subject having a low diastolic blood pressure value is detected is peripheral (downstream) from the cuff. ) Side, there is no waveform component W2 derived from the pressure change (intravascular volume change) due to reflection from the blood vessel, and is derived from the direct pressure change (intravascular volume change) accompanying the pumping of blood from the upstream side of the cuff. Although it is only the waveform component W1, the pulse wave component PW having a smaller pulse wave amplitude value than the waveform component W1 which reflects the actual pressure change (intravascular volume change) is detected due to the elasticity (compliance) characteristic of the cuff. .

As described above, according to the conventional method of determining the minimum blood pressure value in the oscillometric blood pressure monitor, the reflection state from the intravascular pressure change under the cuff to the intravascular volume change, and the intravascular pressure change under the cuff. Accurate measurement of the minimum blood pressure was difficult because the effects of reflexes on the skin and elasticity of the cuff (compliance) were not fully taken into consideration.

That is, in the conventional oscillometric sphygmomanometer, the ratio between the pulse wave amplitude value and the maximum amplitude value at the point of the minimum blood pressure value varies depending on the individual difference of the person to be measured and the measurement conditions (decompression rate, etc.). Therefore, there is a problem in that an error occurs in each measurement because the uniquely determined ratio is used although it cannot be uniquely determined.

[0025]

An object of the present invention is to depend on the change profile of the pulse wave amplitude value superimposed on the cuff pressure, such as using the ratio of the pulse wave amplitude value and the maximum amplitude value at the point of the diastolic blood pressure value. To provide an electronic sphygmomanometer that can accurately measure the minimum blood pressure value without doing so. Another object of the present invention is to provide an electronic sphygmomanometer that can accurately measure the minimum blood pressure value by reducing the influence of the individual difference of the measurement subject and the measurement conditions.

[0026]

In order to achieve this object, the present inventor has conducted extensive research on the analysis of the pulse wave component superimposed on the cuff pressure, and as a result, the pulse wave component near the minimum blood pressure value has been obtained. I was able to find the characteristics peculiar to.

Based on this finding, the above object has been achieved by the following inventions (1) to (4) which do not depend on the change profile of the pulse wave amplitude value. (1) An electronic sphygmomanometer that has a cuff that presses a blood vessel, and determines a minimum blood pressure value based on a pulse wave component that is superimposed on the cuff pressure during the depressurization process of the cuff pressure. A maximum gradient point of the pulse wave component is detected between the bottom point that precedes the peak point and a minimum blood pressure value is determined based on the phase difference between the appearance of the bottom point and the maximum gradient point. An electronic sphygmomanometer characterized in that (2) In the electronic sphygmomanometer that has a cuff that presses a blood vessel and determines the minimum blood pressure value based on the pulse wave component that is superimposed on the cuff pressure in the depressurization process of the cuff pressure, the peak point of the pulse wave component Detecting the maximum gradient point of the pulse wave component between the bottom point occurring prior to the peak point and determining the diastolic blood pressure value based on the time difference between the appearance of the bottom point and the maximum gradient point. An electronic sphygmomanometer characterized by. (3) The minimum blood pressure value is determined by using the displacement of the bottom point occurring before the peak point or the bottom point occurring after the peak point from the maximum gradient point (1) or The electronic blood pressure monitor according to (2). (4) The cuff includes a large cuff for blood vessel ischemia and a small cuff for pulse wave detection, and the large cuff and the small cuff are connected via a fluid resistance (1) to (1). The electronic blood pressure monitor according to any one of (3).

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an electronic blood pressure monitor of the present invention will be described with reference to the preferred embodiments together with its principle contents. <Pressure Force and Pulse Wave Component of Cuff> FIG. 4 is a cross-sectional view in the longitudinal direction of the arm (the direction in which the upper arm extends) when the cuff of the embodiment of the present invention is wound around the upper arm 101. The cuff of the present 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. In FIG. 4, a blood vessel 100 is provided by the pressurized large cuff 1 for vascular ischemia.
Is blocked by Q, and from the upstream side 100a to the downstream side 10a
It is shown that the blood flow to 0b is suppressed.

The force to beat the arm by the large cuff 1 is the strongest in the central portion (the portion A in the figure) in the width direction of the cuff, becomes weaker as it approaches both ends, and becomes almost zero at both ends. The small cuff 2 is provided at the center portion (portion A in the figure) in the width direction of the cuff, and thus the change in intravascular pressure (change in intravascular volume) at this portion is best captured. The "cuff pressure" described in the specification of the present application means the pressure in the cuff, but it is substantially equal to the compressive force of the arm at the center portion (the portion A in the figure) in the width direction of the cuff. From the center of the cuff in the width direction (A in the figure)
It is also the pressure from the cuff applied to the blood vessels below.

As described above, the pulse wave component superimposed on the cuff pressure detected by the small cuff 2 for detecting a pulse wave is a direct pressure change (blood vessel) accompanying the discharge of blood flow from the upstream side of the cuff. Waveform component W1 (hereinafter referred to as W1 waveform) derived from internal volume change and waveform component W2 derived from pressure change (internal volume change) due to reflection from blood vessels on the downstream side of the cuff (hereinafter referred to as
Of these, the W1 waveform is, for convenience, the pressure change below the center portion in the width direction of the cuff, that is, the portion A of FIG. 4 (hereinafter, simply referred to as the cuff center portion A). Waveform component W1-A derived from (volume change in blood vessel)
(Hereinafter, referred to as W1-A waveform) and the upstream portion in the width direction of the cuff, that is, the pressure change (intravascular volume change) under the portion B in FIG. 4 (hereinafter, simply referred to as the cuff upstream portion B). Waveform component W1-B (hereinafter, referred to as W1-B waveform) and the change in intravascular volume under the cuff width direction downstream portion, that is, the portion C in FIG. 4 (hereinafter, simply referred to as cuff downstream portion C). Can be considered separately for the waveform component W1-C (hereinafter referred to as the W1-C waveform) that is derived from. <Characteristics of Waveforms Constituting Pulse Wave Components> In FIG. 5, the W1 waveform is synthesized from the W1-A waveform, the W1-B waveform, and the W1-C waveform, and further, is synthesized with the W2 waveform to obtain the pulse wave component PW. The completed state is schematically shown. The illustrated pulse wave component PW is a typical one when the cuff pressure during the depressurization process is between the systolic blood pressure value and the diastolic blood pressure value. When the cuff pressure during the depressurization process is between the maximum blood pressure value and the minimum blood pressure value, blood flow flows into the central portion A of the cuff, and the blood flow is pulsated to blood vessels downstream of the cuff. Then, in this case, the central portion A of the cuff accompanying the discharge of blood flow to the blood vessel on the downstream side.
The W1-A waveform derived from the change in intravascular volume below and the W1-C waveform derived from the change in intravascular volume under the cuff downstream portion C show changes in intravascular volume due to the blood flow flowing into the cuff upstream portion B. The derived W1-B waveform and the time delay, that is,
A W1 waveform is formed to overlap with a time difference, and further, a W2 waveform due to reflection from the downstream side overlaps with a time difference to form a pulse wave component PW superimposed on the cuff pressure.

Since the small cuff 2 for detecting a pulse wave is attached to the central portion A of the cuff, the W1-A waveform is most easily detected as compared with the W1-B waveform and the W1-C waveform. . Therefore, the characteristics of the W1-A waveform are
Compared with the characteristic of the 1-C waveform, it is largely reflected in the shape of the W1 waveform.

The W1-B waveform shows the intravascular volume change under the cuff upstream portion B. Since the upstream portion B is located on the upstream side (heart side) compared to the central portion A and the downstream portion C, W1-A
It appears earlier than the waveform and the W1-C waveform, and is reflected in the rising shape of the W1 waveform. Regarding the W1-C waveform, the intravascular volume change below the cuff downstream portion C is shown, but the downstream portion C is located on the downstream side of the central portion A, and the compressive force of the cuff in the downstream portion C is the central portion A. Since it is smaller than the pressure force of the cuff, 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 waveform and the W1-C waveform is substantially. There is no way.

Since the W2 waveform is the reflection from the blood vessel on the downstream side of the cuff with respect to the output of the blood flow from the upstream side, the appearance of the peak appears in the W1 waveform depending on the timing when the intravascular pressure on the downstream side becomes higher than the cuff pressure. Although it may be delayed or advanced after the appearance of the peak, FIG. 5 shows the appearance of the peak of the W2 waveform after the appearance of the peak of the W1 waveform. In general, the reflection of the pulse wave component of the shape of the W2 waveform on the overall shape is reflected by the W1 waveform (W1-A waveform, W1-B waveform, W
It is smaller than the reflection of the shape of 1-C waveform composite waveform). Further, when the cuff pressure in the depressurization process is near the minimum blood pressure value, the intravascular pressure on the downstream side of the cuff has sufficiently recovered to the state before the ischemia by the cuff, so that the reflection from the downstream blood vessel is substantially Disappear. Therefore, in the pulse wave component in which the cuff pressure is detected near the minimum blood pressure value, the W2 waveform disappears substantially. <Features of W1-A Waveform> Next, the features of the W1-A waveform will be described in detail.

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

In graph 1, the abscissa represents the elapsed time when the cuff pressure is decompressed at a constant decompression rate, and the ordinate represents the intravascular external pressure difference (intravascular pressure-cuff pressure). Based on the case where the waveform (intravascular pressure change) is simplified by a triangular waveform, the change in intravascular external pressure difference under the central portion A of the cuff derived from the invasive blood waveform (intravascular pressure change) at each point of the elapsed time ( The same triangular waveform as the open blood waveform is shown.

On the upper side of graph 1, the vertical axis is the intravascular volume, and the change in the intravascular volume at each time point that occurs according to the change in the intravascular external pressure difference is shown as graph 2. On the left side of the vertical axis of the blood vessel internal / external pressure difference, the relationship between the blood vessel internal / external pressure difference and the blood vessel internal volume that converts the change in the blood vessel internal / external pressure difference (graph 1) into the change in the blood vessel internal volume (graph 2) is plotted on the horizontal axis. Is shown as graph 3.

Regarding the relationship between the blood vessel internal / external pressure difference and the blood vessel internal volume in Graph 3, a simplified relationship is drawn by paying attention to the tendency that the blood vessel internal volume changes abruptly (abrupt increase or decrease) in the vicinity of the intravascular external pressure difference. I'm assuming. That is, the change between the state where the blood vessel is completely closed (internal volume 0) and the state where it is completely open (internal volume Vmax) in the process of increasing / decreasing the pressure difference between the internal pressure and the external pressure, It has two folds at a point, and the steep part between V0 and V1 and below V0 and V
It is represented by a polygonal line consisting of straight lines with a gentle slope of 1 or more.

At the position where the pressure difference between the inside and outside of the blood vessel is 0, the blood vessel is collapsed due to its own weight (intravascular volume V0). However, when the difference between the inside and outside pressure of the blood vessel changes to a positive value from this position, the intravascular volume suddenly changes. Increases and reaches a state where the blood vessel is sufficiently opened (intravascular volume V1), and thereafter gradually increases with respect to changes in the intravascular external pressure difference (maximum intravascular volume Vmax
And a tendency that the blood vessel internal / external pressure difference changes from a position of 0 to a negative value, the blood vessel internal volume gradually decreases (toward the blood vessel internal volume 0). In Graph 3, the portion of the steep slope between the intravascular volume V0 and V1 is approximated by a straight line, so the rate of change in the intravascular volume is the same during this period. Internal / external pressure difference is 0
The rate of change at the position (position of the intravascular volume V0) is maximum.

In such a blood vessel volume, the pressure difference between the blood vessel inside and outside is 0.
The degree of the tendency of sudden change (rapid increase) in the vicinity of is dependent on the degree of vascular extensibility of the subject, but the tendency itself is considered to be generalizable.

In graph 1, in the depressurization process (elapsed time) of the cuff pressure, a is at a time point when the cuff pressure is equal to the systolic blood pressure value, and b is 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 pressure difference between the inside and outside of the blood vessel under the central portion A of the cuff when the cuff pressure is equal to the minimum blood pressure value.

Changes in the pressure difference between the inside and outside of the blood vessel (triangular waveforms) at each point in the elapsed time (triangles) are peaks (peak points) of the systolic blood pressure value (change in pressure inside the blood vessel). That is, it is derived from the early diastole of the heart, and the downward apex (bottom point) is derived from the portion of the lowest blood pressure value in the open waveform (intravascular pressure change) (that is, the early systole of the heart). To do.

The change in the intravascular / external pressure difference of a, b, and c of these graphs 1 is converted into the change of the intravascular volume using the relationship between the intravascular external pressure difference and the intravascular volume in graph 3 as shown in graph 2 ( a), (b), (c). (A),
In (b) and (c), the position of the early systole of the heart (front and rear 2
Location) is indicated by a white circle. This corresponds to the downward peak (bottom point) of the open blood waveform (intravascular pressure change).
The waveform (indicated by a thick line) between the positions of the heart in the early systole (two positions before and after) is the W1-A waveform.

That is, in graph 2, the W1-A waveform is
It is shown that the cuff pressure changes at each point in the depressurization process (elapsed time).

In the W1-A waveforms (volume change in blood vessel) of (b) and (c), the position where the pressure difference between the inside and outside of the blood vessel is 0 prior to the peak point is indicated by a dot. (A) W1-A
In the waveform (change in intravascular volume), the peak point corresponds to the 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 in (a), (b), and (c) is 0 is actually the part where the intravascular volume increases (suddenly increases) (the maximum gradient in the first half of the waveform). Points).

Further, W1-A of (a), (b) and (c)
In the waveform, a dot also indicates the position where the intravascular volume that occurs after the peak point is minimized. It is known that the position where the intravascular volume that occurs after the peak point of the W1-A waveform becomes minimum is approximately equal to the position of the downward peak point (bottom point) of the actual pulse wave component. Therefore, in the following, W
The position at which the intravascular volume that occurs after the peak point of the 1-A waveform is minimized is called the bottom point of the W1-A waveform.

In Graph 2, the portion of the W1-A waveform where the intravascular volume suddenly rises (the maximum gradient point in the first half of the waveform) [the position where the intravascular external pressure difference indicated by the dot is 0] is W1-A.
The time (time difference) delayed from the position of the early systole preceding the waveform is indicated by t1, and the time (time difference) that the bottom point of the W1-A waveform advances from the position of the next early systole.
Is indicated by t2, and one period of the pulse wave component is indicated by T. Here, the period T of the pulse wave component is substantially constant during the measurement. Further, H represents a downward displacement from a portion (the maximum gradient point in the first half of the waveform) where the intravascular volume at the bottom point of the W1-A waveform sharply rises.

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 the continuously generated W1-A waveform are almost the same, t is the steeply rising portion of the W1-A waveform of interest (the maximum slope point in the first half). W1-preceding
It is considered to indicate a delay time (time difference) from the bottom point of the A waveform, that is, a time difference of appearance of the maximum gradient point from the preceding bottom point (of the W1-A waveform).

As shown in (a), (b) and (c) of graph 2, the time difference t1 and the time difference t2 become smaller as the cuff pressure approaches the minimum blood pressure value from the maximum blood pressure value.
That is, the time difference t of appearance of the maximum gradient point from the preceding bottom point becomes smaller as the cuff pressure approaches the minimum blood pressure value from the maximum blood pressure value. The period T of the pulse wave component is
Since it is substantially constant during the measurement, the phase difference 2π (t /
Similarly, T) decreases as the cuff pressure approaches the minimum blood pressure value from the maximum blood pressure value.

Then, as shown in (c) of graph 2,
At the time when the cuff pressure becomes equal to the diastolic blood pressure value, under this simplified graph, the preceding bottom point of the W1-A waveform, the maximum slope point (spike point), and the early systole simultaneously occur, and t1 = 0, t2 = 0, and t = 0.

Furthermore, from (b) and (c) of graph 2,
It is also shown that the downward displacement H from the maximum gradient point (rapid rise point) of the bottom point of the W1-A waveform becomes smaller as the cuff pressure approaches the minimum blood pressure value. Then, 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 of the W1-A waveform and the position of the maximum gradient point are equal to each other under this simplified graph. H = 0
(There is no displacement).

From these facts, the following two characteristics (1) '(2)' can be found for the actual W1-A waveform. (1) 'W1-A waveform steep rising part (maximum slope point)
From the bottom point (time difference t or phase difference 2π
(T / T) becomes smaller as the cuff pressure approaches the minimum blood pressure value. (2) 'W1-A steep rising part of waveform (maximum slope point)
The displacement H at the bottom point becomes smaller as the cuff pressure approaches the minimum blood pressure value. <Characteristics of pulse wave component> As described above, the pulse wave component PW is divided into partial waveforms, and the simplified examination contents of the W1-A waveform are shown. However, in reality, the pulse wave component PW is the W1-A waveform. And W
It is detected by the pulse wave detecting small cuff 2 as one pulse wave component without being separated into a 1-B waveform or the like.

However, as described above, although the W1-B waveform is reflected in the rising portion of the W1 waveform, W1-B waveform is reflected.
The A waveform largely reflects the shape of the W1 waveform of the pulse wave component superimposed on the cuff pressure. Further, the W2 waveform of the pulse wave component is generally smaller than the W1 waveform, and disappears when the cuff pressure is near the minimum blood pressure value.

Therefore, the characteristics of the detected pulse wave component are also the same as the examination contents in <W1-A waveform characteristics>.
The following two features can be found. (1) Delay from the bottom point of the steeply rising portion (maximum slope point) of the pulse wave component (time difference t or phase difference 2π (t /
T)) becomes smaller as the cuff pressure approaches the diastolic blood pressure value. (2) The displacement H at the bottom point from the steeply rising portion (maximum slope point) of the pulse wave component becomes smaller as the cuff pressure approaches the minimum blood pressure value.

The waveforms of (B) and (C) of FIG. 7 are obtained at respective times when (b) and (c) of FIG. 6 are obtained, that is, when the cuff pressure is between the systolic blood pressure value and the diastolic blood pressure value. It is the pulse wave component superposed on the actually detected cuff pressure at the time of the lowest blood pressure value. In each pulse wave component, the steep rising portion (maximum slope point) Um in the first half, the peak point Pe, and the peak point Pe
Bottom points B1 and B2 that occur before or after
It is shown. Further, the figure shows the time difference t of the maximum gradient point Um from the bottom point B1, the cycle T, and the downward displacement H of the bottom point B2 from the maximum gradient point (sudden rising point) Um. The bottom point B1 is also the bottom point B2 that occurs later than the peak point of the pulse wave component that occurs earlier, and the pulse wave components that occur continuously have almost the same shape. The displacement of the point B2 from the maximum gradient point (sudden rising point) Um is almost the same as the displacement of the bottom point B1 from the maximum gradient point (sudden rising point) Um.

As described in the above characteristics (1) and (2), at the time of the diastolic blood pressure value, the time difference t (phase difference 2π (t / T)) and the displacement H are between the diastolic blood pressure value and the diastolic blood pressure value. It looks smaller than that. <Measurement of the minimum blood pressure value> Based on the characteristics (1) and (2) of the pulse wave component, the inventor of the present application confirmed the following two validity as the measurement method of the minimum blood pressure value. [1] The cuff pressure at the time when the phase difference between the appearance of the bottom point occurring before the peak point of the pulse wave component and the appearance of the maximum gradient point (sudden rising point) becomes smaller than a predetermined threshold value is the minimum blood pressure value. [2] The cuff pressure at the time point when the displacement from the maximum gradient point (sudden rising point) of the bottom point that precedes or lags the peak point of the pulse wave component becomes smaller than a predetermined threshold is the minimum blood pressure value.

The bottom point and the maximum gradient point (sudden rising point) of the pulse wave component in [1] and [2] are detected in the individual pulse wave components. The predetermined threshold values in [1] and [2] are set in consideration of noise and the like in the signal processing process of the detected pulse wave. The influence of measurement conditions such as individual difference and depressurization rate on noise in the signal processing process is small. As in the conventional oscillometric sphygmomanometer, the measurement method of the minimum blood pressure value of [1] and [2] is a parameter (minimum blood pressure) that is greatly affected by individual differences of the measurement subject and measurement conditions (decompression rate, etc.). It is not necessary to deal with the change profile of the pulse wave amplitude value during the decompression process of the cuff pressure using the ratio of the pulse wave amplitude value at the value point to the maximum pulse wave amplitude value). From this, [1]
By the method of measuring the diastolic blood pressure value of [2], it is possible to realize accurate measurement of the diastolic blood pressure value by reducing variations due to individual differences and measurement conditions (decompression rate, etc.).

The present invention is based on the method [1] for measuring the diastolic blood pressure value. <Examples> Hereinafter, preferred examples of the present invention will be described in detail.

FIG. 8 is a block diagram showing an air system and a measurement system of the electronic sphygmomanometer according to the embodiment of the present invention.

The large cuff 1 for blood vessel ischemia is connected via a tube 11 to a pressurizing pump 3 and a pressure reducing control valve (electromagnetic valve) 4. Further, the large cuff 1 is connected to the pressure sensor 5 via the fluid resistance 13. Further, the small cuff 2 for detecting a pulse wave is located substantially at the center of the large cuff 1, and is connected to the pressure sensor 5 via the tube 12. For blood pressure measurement using these double cuffs, the previous application by the same applicant,
It is described in detail in JP-A-2000-79101.

The small cuff 2 for pulse wave detection is provided at the center of the cuff of the large cuff 1 for blood vessel ischemia, and it best captures the change in intravascular volume at the center of the cuff. Further, the small cuff 2 is as small as possible in order to reduce the reduction of the pulse wave component due to the diffusion of the pulse wave vibration. Fluid resistance 1
Reference numeral 3 denotes a mechanical filter for reducing or blocking the pulse wave component detected by the large cuff 1, which allows the small cuff 2 to accurately detect the intravascular volume change under the cuff.

As the pressure sensor 5, a diaphragm type pressure-electric converter using a semiconductor pressure gauge is used.

The output signal (pressure signal) of the pressure sensor 5 is amplified by the amplifier 6 and passed through the low pass filter 7 to A /
Digitally converted by D converter (converter) 8 CPU 9
Entered in. The low pass filter 7 limits the frequency band of the output signal and cuts unnecessary high frequency noise such as valve control noise. Cut-off frequency is 10-30
It is set to Hz.

The pressurizing pump 3 and the pressure reducing control valve (electromagnetic valve) 4 are controlled by the CPU 9. In particular, the pressure reducing control valve (solenoid valve) 4 is controlled to be opened / closed (PWM control) by a PWM signal (on / off pulse signal) from the CPU 9 so that the PWM signal is changed from completely “closed” to completely “open”. By changing the duty, the opening orifice area can be continuously controlled.

Further, the CPU 9 periodically takes in a digitally converted pressure signal (cuff pressure signal) from the A / D converter (converter) 8 and extracts a pulse wave signal (pulse wave) superposed on the cuff pressure signal. It has a function of separating the components) and determining the systolic blood pressure value and the diastolic blood pressure value from the pulse wave signal and the cuff pressure (signal). The determination of the systolic blood pressure value is not particularly limited in the present invention, but in this embodiment, the peak information of the pulse wave component described in the prior application by the same applicant, Japanese Patent Laid-Open No. 2000-287945. Is determined using. In addition, the minimum blood pressure value is, as described above, the maximum slope point (point of maximum slope) detected between the bottom point and the peak point which precedes the peak point of the pulse wave component, and the appearance of the bottom point. The time difference t is calculated and determined based on this time difference t. In particular, instead of directly handling the time difference t, the time difference t
Phase difference 2π (t
/ T) (since the value of t / T is handled in the calculation of the present embodiment, t / T is hereinafter referred to as a phase difference), it is possible to further eliminate variations in measurement by the person to be measured. .

The CPU 9 also has a function of displaying the systolic blood pressure value and the diastolic blood pressure value thus determined on the display LCD 10.

FIG. 9 is a flow chart showing the outline of the specific processing operation of the electronic sphygmomanometer according to the embodiment of the present invention.

Measurement start SW (switch) of the electronic sphygmomanometer
When the switch is turned on (ST1), the pressure reducing control valve 4 is completely closed.
(ST2) is reached, and the drive of the pressure pump 3 is started (ON) under the control of the CPU 9 (ST3). When the pressurizing pump 3 is driven, reading of the cuff pressure is started (ST
4) It is determined whether or not the read cuff pressure has reached a pressure value (set pressure) that is sufficiently higher than the preset maximum blood pressure value (ST5). The pressurizing pump is driven until the cuff pressure reaches the set pressure, and when the cuff pressure reaches the set pressure, the drive of the pressurizing pump 3 is stopped (OFF) (ST).
6).

Then, the CPU 9 of the pressure reduction control valve 4 controls the slow speed exhaust to start the slow speed pressure reduction at a predetermined pressure reduction rate (for example, 2 to 3 mmHg / sec) (ST7). In the depressurization process, the CPU 9 reads the cuff pressure at predetermined time intervals (every sampling time) (ST8), and the pulse wave component superimposed on the cuff pressure is extracted (ST9). Then, first, peak information is detected from the extracted pulse wave component, and the systolic blood pressure value is determined based on the peak information (ST10). next,
Further, the cuff pressure is continuously read in the process of reducing the cuff pressure (ST11), and the pulse wave component is extracted (S1).
2) The pulse wave component is extracted to determine the minimum blood pressure value (S
13).

After the determination of the minimum blood pressure value, the pressure reducing control valve is fully opened (fully "opened") to return the cuff pressure to the atmospheric pressure (ST14). Then, the stored maximum blood pressure value and minimum blood pressure value are displayed on the LCD 10 under the control of the CPU 9 (S
T15).

FIG. 10 is a CPU for determining the diastolic blood pressure value in the portion surrounded by the broken line from S11 to S13 in FIG.
The processing operation of is shown in a more detailed flowchart.

The cuff pressure P is detected at predetermined time intervals (every sampling time) even after the systolic blood pressure value is determined (S
(T100), the pulse wave component superimposed on the cuff pressure (see the pulse wave component diagram in FIG. 7) is extracted (ST101). From the pulse wave component, continuous bottom points B1 and B2 and peak points Pe between them are detected (ST102, ST103, ST
104) between the bottom point B1 (bottom point occurring before the peak point) and the peak point Pe, that is, the first half of the pulse wave component, the point having the maximum gradient (maximum gradient point) Um.
Is detected (ST105). The time difference t between the bottom point B1 and the point having the maximum gradient (maximum gradient point) Um is t.
Is calculated (ST106). Further, the time interval T between the appearance of the bottom point B1 and the bottom point B2 is calculated (ST107),
The phase difference (t / T) is calculated (ST108). here,
Since the bottom point B2 becomes the bottom point B1 of the next pulse wave component, the time interval T is a pulse wave interval and also a pulse cycle.

When this phase difference (t / T) becomes smaller than a predetermined threshold value k, the cuff pressure P at that time is determined as the minimum blood pressure value (ST110). When the phase difference (t / T) is equal to or greater than the predetermined threshold value k, similar processing is sequentially performed for the next pulse wave component superimposed on the further reduced cuff pressure to determine the minimum blood pressure value. .

FIG. 11 is a more detailed flowchart showing the processing operation of the CPU for determining the systolic blood pressure value in another embodiment for the part surrounded by the broken line from S11 to S13 in FIG. .

The part different from the flowchart of FIG.
The point is that steps ST200 and ST201 surrounded by a broken line are provided between ST109 and ST110, and other points are the same as those in the flowchart of FIG.

ST200 and ST201 are based on the measuring method of the minimum blood pressure value of [2] described in <Measurement of minimum blood pressure value>. That is, the displacement H of the bottom point B2 from the steep rising portion (maximum gradient point) Um of the pulse wave component is calculated (ST200). Then, when the displacement H becomes smaller than a predetermined threshold value h (ST201), the cuff pressure at that time is determined as the minimum blood pressure value (ST110).

When the displacement H is equal to or greater than the predetermined threshold value h, the process returns to ST100 to extract the next pulse wave component superimposed on the further reduced cuff pressure (ST101), and ST1.
The series of processing from 02 to ST109, ST200, and ST201 is sequentially performed to determine the minimum blood pressure value.

As described above, since the displacements of the bottom point B1 and the bottom point B2 are almost the same, S
T200 can be replaced with the step of calculating the displacement H'of the bottom point B1 from the maximum gradient point Um, and ST201 can be replaced with the step of comparing the displacement H'with the threshold value h.

In the embodiment shown in the flowchart of FIG. 11, there are two methods of measuring the minimum blood pressure value, [1] and [2] described in <Measurement of minimum blood pressure value>.
Confirmed to be the lowest blood pressure value by one measurement method (ST10
9, ST201), the lowest blood pressure value (ST1
Since 10) is determined, the accuracy of determination of the minimum blood pressure value is further improved.

The preferred embodiments of the electronic blood pressure monitor of the present invention have been described above, but the present invention is not limited to these.

[0080]

As described above, in the electronic sphygmomanometer of the present invention, the change profile of the pulse wave amplitude value of the pulse wave component superposed on the cuff pressure during the depressurization process of the cuff pressure is not used, and Since the minimum blood pressure value is determined based on the phase difference (time difference) between the maximum slope point and the peak point between the bottom point and the peak point that occur prior to the peak point, the extensibility of blood vessels, The magnitude of pulse pressure (= systolic blood pressure − diastolic blood pressure),
It is possible to reduce variations in measured values due to individual differences such as pulse rate and measurement conditions such as decompression rate, and it is possible to accurately measure the minimum blood pressure value.

Further, since the diastolic blood pressure value is determined by using the displacement of the bottom point of the pulse wave component from the maximum gradient point, the diastolic blood pressure value can be measured more accurately.

Further, since the cuff is composed of a large cuff for blood vessel ischemia and a small cuff for pulse wave detection, and the large cuff and the small cuff are connected via a fluid resistance, it is possible to accurately detect the pulse wave component. Therefore, the minimum blood pressure value can be stably and accurately measured.

[Brief description of drawings]

FIG. 1 is a diagram showing a state in which a pulse wave component is superimposed on a cuff pressure during a process of reducing the cuff pressure.

FIG. 2 is a diagram showing how the amplitude value of the pulse wave superimposed on the cuff pressure changes during the process of reducing the cuff pressure.

3A and 3B schematically show a pulse wave component near the point where the maximum pulse wave amplitude value appears in FIG. 2 and a pulse wave component near the point where the cuff pressure is equal to the diastolic blood pressure value, respectively. FIG.

FIG. 4 is a longitudinal sectional view of the arm when the cuff according to the embodiment of the present invention is wrapped around the upper arm and the cuff is pressed.

FIG. 5 is a diagram schematically showing that a pulse wave component is composed of several waveforms.

FIG. 6 is a diagram schematically showing how a waveform derived from a change in blood vessel volume under the central portion of the cuff is generated and changed during the process of reducing the cuff pressure.

FIG. 7 is a diagram showing pulse wave components superposed on actually detected cuff pressures at times when the cuff pressure is between the systolic blood pressure value and the diastolic blood pressure value and at the time when the diastolic blood pressure value is present.

FIG. 8 is a block diagram showing an air system and a measurement system of the electronic sphygmomanometer according to the embodiment of the present invention.

FIG. 9 is a flowchart showing an outline of processing operation of the electronic blood pressure monitor according to the embodiment of the present invention.

FIG. 10 is a flowchart showing an outline of determination of the minimum blood pressure value of the electronic blood pressure monitor according to the embodiment of the present invention.

FIG. 11 is a flowchart showing an outline of determination of the minimum blood pressure value of the electronic sphygmomanometer according to another embodiment of the present invention.

[Explanation of symbols]

1 ... Large cuff 2 ... small cuff 3 ... Pressure pump 4 Decompression control valve 5 ... Pressure sensor 6 ... Amplifier 7 ... Low-pass filter 8 ... A / D converter 9 ... CPU 10 ... LCD 11, 12 ... tube 13 ... Fluid resistance 100 ... blood vessels 100a ... upstream side of blood vessel (heart side) 100b ... Downstream of blood vessel (peripheral side) 101 ... arm

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takahiro Soma             1500 Inoguchi, Nakai-cho, Ashigarakami-gun, Kanagawa Prefecture             Terumo Corporation F-term (reference) 4C017 AA08 AC01 BC23 FF05

Claims (4)

[Claims] 1. A peak of a pulse wave component in an electronic sphygmomanometer having a cuff for compressing a blood vessel, wherein a minimum blood pressure value is determined based on a pulse wave component superposed on the cuff pressure in a depressurization process of the cuff pressure. Between the point and the bottom point that precedes the peak point, detects the maximum gradient point of the pulse wave component, based on the phase difference between the appearance of the bottom point and the maximum gradient point, the minimum blood pressure value. An electronic sphygmomanometer characterized by making a decision. 2. A peak of a pulse wave component in an electronic sphygmomanometer having a cuff for compressing a blood vessel, wherein a minimum blood pressure value is determined based on a pulse wave component superimposed on the cuff pressure in the process of reducing the cuff pressure. Between the point and the bottom point that precedes the peak point, the maximum gradient point of the pulse wave component is detected, and the minimum blood pressure value is determined based on the time difference between the appearance of the bottom point and the maximum gradient point. An electronic blood pressure monitor characterized by: 3. The minimum blood pressure value is determined by using the displacement of the bottom point occurring prior to the peak point or the bottom point occurring after the peak point from the maximum gradient point. The electronic blood pressure monitor according to claim 1 or claim 2. 4. The cuff comprises a large cuff for blood vessel ischemia and a small cuff for pulse wave detection, and the large cuff and the small cuff are connected via a fluid resistance. 1
The electronic blood pressure monitor according to claim 3.