JP4475480B2 - Electronic blood pressure monitor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sphygmomanometer that measures blood pressure based on a change in arterial wall vibration accompanying a change in cuff pressure, and particularly has a feature in determining whether or not the cuff winding state used for measurement is appropriate. Is.
[0002]
[Prior art]
As a device for measuring a subject's systolic blood pressure (maximum blood pressure), an arm band or cuff is wrapped around the subject's arm or wrist and the cuff is pressurized to a pressure value equal to or higher than the systolic blood pressure, thereby blocking the artery and reducing blood flow. An oscillometric method is known that detects vibration due to arterial pulsation by continuously observing pressure fluctuations inside the compression cuff after ischemia and measures systolic blood pressure from changes in the amplitude of this vibration. Yes. However, in the oscillometric method, vibration is detected even when the cuff pressure is equal to or higher than the systolic blood pressure, so that the moment of opening of the blocked artery serving as the systolic blood pressure point cannot be captured. For example, Japanese Patent Laid-Open No. 5-269089 The method of acquiring the vibration of only the position where the artery is blocked is disclosed.
[0003]
[Problems to be solved by the invention]
However, to measure accurately with these methods, it is necessary to pay attention to the wrapping of the armband and acquire the pulse wave accurately, equivalent to or better than the conventional oscillometric method. When the winding at the time is not appropriate, there is a drawback that sufficient performance cannot be maintained.
Conventionally, as shown in Japanese Patent Publication No. 56-43734, a method of detecting the armband by using the time required to pressurize the cuff to a predetermined pressure has been used.
[0004]
However, in clinical practice, blood pressure measurement is performed using several cuffs of different sizes in order to cope with infants to adult obese patients. For example, when a large cuff for obesity is used, it takes more time to pressurize than a normal cuff, so that it may be erroneously detected that the winding is poor. Moreover, when pressurizing manually using an air balloon, the method using the pressurization time described above cannot be used.
An object of the present invention is to provide a sphygmomanometer that can determine whether cuff winding is appropriate by detecting a peak state of a pulse wave detected from a cuff.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, the present invention comprises the following arrangement.
(1) An electronic sphygmomanometer that has a pressure cuff that compresses a blood pressure measurement site and a measurement cuff that measures vibration of the arterial wall, and measures blood pressure based on a change in the vibration of the arterial wall accompanying a change in the cuff pressure in the possess a peak detection means for detecting a peak from the vibration signal by the measuring cuff, and a state determining means wound determining the winding state of the cuff using a signal detected by the peak detecting means, the winding state The determining means is that the cuff winding is not appropriate when observing the peak of the pulse wave that is observed at the time of proper winding and the peak that is opposite in polarity, among the plurality of peaks detected by the peak detecting means. An electronic blood pressure monitor characterized by determining .
[0006]
(2) The electronic sphygmomanometer according to (1), wherein the measurement cuff measures the vibration of the arterial wall at an arbitrary position from the approximate center of the compression cuff to the downstream end in the blood flow direction.
(3) The electronic sphygmomanometer according to (1), wherein the measurement cuff measures the vibration of the arterial wall at a substantially central position of the compression cuff.
(4) The electronic sphygmomanometer according to (1), wherein the measurement cuff measures the vibration of the artery wall in the vicinity of the position of the artery to be closed with a pressure in the vicinity of the maximum blood pressure of the compression cuff.
[0007]
(5) The sphygmomanometer according to any one of (1) to (4), wherein the winding state determination unit includes a notification unit that notifies a determination result.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, in order to further clarify the gist of the sphygmomanometer according to the present invention, embodiments will be described with reference to the drawings.
[0009]
<Configuration example of blood pressure monitor of the present embodiment>
FIG. 1 is a diagram showing a schematic configuration example of the electronic sphygmomanometer according to the present embodiment.
In FIG. 1, 10 is a cuff band having the configuration of the present embodiment, and 20 is a measurement unit that recognizes a blood pressure value from vibration of the cuff internal pressure while controlling the pressure of the cuff band 10. Since the detailed configuration of the cuff belt 10 will be described below, a configuration example of the measurement unit 20 will be described here.
[0010]
21 is a pressure increasing unit including a pump, and 22 is a pressure reducing unit including a pressure reducing valve. For example, in a sphygmomanometer that measures only at the time of depressurization according to control of the control unit 24, the pressure increasing unit (pump) 21 sets the systolic blood pressure value. After the pressure is rapidly increased to a pressure exceeding the pressure and the pressure increase is stopped, the pressure reduction unit 22 performs pressure reduction at a constant speed of, for example, 2 to 3 mmHg / sec. Reference numeral 23 denotes a pressure measuring unit that receives a pressure signal superimposed with vibration from the pressure sensor with a built-in cuff of this example, performs A / D conversion, and outputs it to the control unit 24. Note that the pressure measurement unit 23 may include circuits such as a low-pass filter and a peak hold, and output an amplitude value of the vibration waveform.
[0011]
A control unit 24 includes a CPU for arithmetic control, a ROM for storing control programs and fixed parameters, and a work RAM for temporary storage. The control unit 24 separates the output value from the pressure measurement unit 23 into a vibration component and a cuff pressure component, stores the vibration amplitude in the RAM corresponding to the cuff pressure, and recognizes the blood pressure value from the pattern of the change. Are displayed on the display unit 25. The operation unit 26 includes operation buttons such as reset and start.
[0012]
<Configuration example of cuff belt of this embodiment>
FIG. 2 is a diagram illustrating a configuration example of the cuff belt 10 according to the present embodiment.
In FIG. 2, reference numeral 11 denotes a compression cuff for compressing a blood vessel, and it needs a size sufficient to apply a sufficient ischemic pressure to the measurement site.
12 is a measurement cuff for detecting the vibration of the pulse wave provided in the substantially central portion of the compression cuff 11, in order to reduce the phenomenon of the wave height due to the diffusion of the vascular vibration in the central portion of the compression cuff. Make it as small as possible.
[0013]
The central portion of the compression cuff 11 provided with the measurement cuff 12 is a portion having the largest crushing force at which the blood vessel is capped. The fluid resistance 14 and the pouch 15 act as a mechanical filter for reducing or blocking vibration noise applied to the measurement cuff 12. In this example, the fluid resistance (orifice) 14 is, for example, a metal thin tube having an outer diameter of 0.45 mm and an inner diameter of 0.20 mm, and is preferably as close to the measurement cuff 12 as possible. The pouch 15 is a pouch as an air chamber that acts as a compliance of the mechanical filter.
[0014]
Reference numeral 16 denotes a pressure sensor that detects the internal pressure of the measurement cuff 12, and it is desirable that the measurement cuff 12 and the pressure sensor 16 be connected by a highly rigid pipe. Alternatively, a sensor can be placed in the cuff.
[0015]
FIG. 3 is a longitudinal sectional view (a cross section in the direction in which the upper arm extends) viewed from the direction A in FIG. 1 when the cuff belt 10 of the present embodiment is wound around the upper arm 31. In FIG. 3, the compression cuff 11 is pressurized, the blood vessel 32 is blocked at point C, and blood flow from the upstream side 32 a to the downstream side 32 b is suppressed. Reference numeral 43 denotes a backing for covering and fixing the outer side so that the pressure of the cuff 11 for compression effectively becomes the pressure of ischemia. In order to reduce the dead volume between the upper arm and the backing, this outer backing has a degree of freedom in the circumferential direction of the arm but restricts the degree of freedom in the longitudinal direction so that it can adhere to the upper arm regardless of the shape of the arm. It is desirable to make a cut substantially perpendicular to the longitudinal direction of the cuff strip 10.
[0016]
Here, as shown in FIG. 3, when the blood vessel at point C is blocked, vibration due to the pulsation of the artery is not transmitted due to ischemia on the downstream side of point C, but on the upstream side of point C, Vibration due to pulsation is transmitted to the measurement cuff 12, and this vibration is detected by the pressure sensor 16.
[0017]
When the pressure cuff 11 is gradually depressurized from the ischemic state shown in FIG. 3, the blood vessel at the point C is opened and the blood flow begins to flow to the peripheral side. FIG. 4a) shows the vibration waveform detected by the pressure sensor 16 at the time when blood flow begins to flow. The first peak A and the second peak B in FIG. 4 a) are peaks caused by changes in blood flow passing through the cuff part as the heart beats captured by the measurement cuff 12.
[0018]
In the sphygmomanometer in which the vibration detecting means is provided inside the compression cuff as described above, there is a phenomenon in which two peaks due to blood flow waves passing through the cuff portion appear as the heart beats. Is recognized. The third peak C is a peak due to reflection of the pressure pulse wave transmitted to the periphery. In the present invention, since the third peak C is not used, the third peak C may be processed so as not to be detected by a filtering process or the like. D is the rising start point of pulsation.
[0019]
FIG. 5c) shows the vibration waveform detected by the pressure sensor 16 where the blood flow begins to flow to the distal side as in FIG. 4a), but the measurement is performed by gently wrapping the cuff upstream side compared to the case of FIG. 4a). I'm doing it. At this time, it is recognized that the first peak A ′ in FIG. 5c) has a peak in the opposite direction to the first peak A in FIG. 4a). This is because, when the upstream side of the compression cuff 11 shown in FIG. 3 is pushed by the vibration of blood flow (above the paper surface), the tightening is weak, so that the measurement cuff 12 and the compression cuff 11 are above the paper surface. It is considered that the pressure value inside the measurement cuff 12 is lowered by being lifted up and separated from the living body, resulting in a negative peak as shown in FIG. 5c).
[0020]
On the other hand, when the cuff is sufficiently tightened, even when the upstream side of the compression cuff 11 is pushed by the blood flow vibration (above the paper surface), the backing cuff 11 and the measurement cuff 11 Since the cuff 12 is restrained from being lifted, it is considered that the close contact with the living body is maintained and a negative peak due to a pressure drop does not occur.
[0021]
FIG. 6 is a block diagram of a part for determining whether or not winding is appropriate in the present embodiment. In FIG. 6, the signal output from the pressure sensor 16 is amplified and noise-discriminated by a filter, an amplifier, etc., A / D converted by an A / D converter, and then output as a digital signal to a differentiator. . The differentiation unit differentiates the digital signal and outputs it to the rising edge detection unit.
[0022]
The rising / falling start point detecting unit sets a threshold value for the signal obtained from the differentiating unit, and detects the starting point D shown in FIG. The falling start point D ′ shown in FIG. When the rising start point D is detected by the rising / falling start point detection unit, a first peak detection unit that detects the first peak A shown in FIG. Two peaks A and B are respectively detected by the second peak detection unit for detecting the peak B of the first, and the comparison unit for comparing the peak height and direction of the two peaks and the determination unit based on the data of the comparison unit Whether or not the winding is appropriate is determined.
[0023]
On the other hand, when the falling start point D ′ is detected, the first peak detecting unit for detecting the first peak A shown in FIG. 4B) and the second peak B shown in FIG. The two peaks A and B are respectively detected by the second peak detector, and the comparison unit for comparing the peak height and the peak direction of the two peaks and whether the winding is appropriate or not by the judging means based on the data of the comparison unit It is determined whether or not. When the winding is loose, the polarity of the first peak may be opposite to that of the second peak. Therefore, when the first peak A ′ as shown in FIG. 5c) is detected, the winding is bad. Judge.
[0024]
When it is determined that the winding is not accurate, it is sent to a notification means for notifying the measurer such as a buzzer or a screen display. Alternatively, it is possible to take appropriate measures such as stopping measurement and performing re-measurement by being sent to a control system such as an MPU. It is also possible to store in a memory or print by a printer so that a history remains when time passes.
[0025]
When the winding is appropriate, blood pressure is continuously measured, and values such as systolic period, diastolic period, average blood pressure, and pulse are determined.
Further, not only the two-step determination of whether the winding is correct or incorrect, but also the winding accuracy can be displayed in several steps. For example, by using an expression such as “slightly loose” as an intermediate stage between correct and inaccurate, the measurer can confirm the high credibility of the measurement value.
In addition, even if the same upward peak as shown in FIG. 5c) is detected, if the winding is loose, the peak value of the first peak may be low, so a threshold value is provided for the peak value of the peak, It is also possible to determine that the winding is bad when it is below the threshold.
[0026]
FIG. 7 explains each part of FIG. 6 using a flowchart. After pressurizing to the vicinity of the average blood pressure with the pump, first, in step S1, it is checked whether the differential value calculated by the differential unit in FIG. 6 is equal to or greater than a threshold value. Data is stored with the point as the rising start point. On the other hand, if it is equal to or less than the negative threshold, the data is stored in step S2 with that point as the falling start point.
[0027]
In step S3, the point at which the differential value becomes 0 is detected after detecting the rising start point, and when confirmed, this point is stored as the first peak in step S4, and the pulse height of the pulse wave of the first peak is calculated from the original waveform. To do. In step S5, after detecting the first peak, the zero cross point where the differential value becomes positive to negative is checked, and in step S6, this point is set as the second peak, and the pulse wave height at this time is calculated from the original waveform.
[0028]
If no peak is detected for a certain period of time after the first peak is detected, the second peak is not detected in step S7, and there is a high possibility of noise instead of a pulse. Move on to vibration waveform detection. If both the first and second peaks are detected, the second peak is stored in step S8, the peak values of the two peaks are compared in step S9, and if the ratio is positive, The blood pressure measurement is continued, and if the ratio is negative, it is determined that the winding is loose, and the process proceeds to a process when winding is inappropriate.
[0029]
The upper diagram of FIG. 8 shows changes in the pressure of the measurement cuff 12 in the process of pressurizing the compression cuff 11 and the measurement cuff 12. The lower diagram in FIG. 8 is an enlarged waveform in the horizontal axis (time axis) direction near the region A ′ in the waveform after passing through a filter with a time constant of 0.1 sec in order to extract the AC component of the pressure change in the upper diagram. It is.
In the lower diagram of FIG. 8, two peaks a′1 and b′1 in the same direction are seen at the rising portion of the vibration waveform for each beat.
[0030]
The upper diagram in FIG. 9 shows changes in the pressure of the measurement cuff 12 in the process of pressurizing the compression cuff 11 and the measurement cuff 12. The lower diagram in FIG. 9 is an enlarged waveform in the horizontal axis (time axis) direction near the region A in the waveform after passing through a filter having a time constant of 0.1 sec in order to extract the AC component of the pressure change in the upper diagram. is there.
In the lower diagram of FIG. 9, after a negative peak a is seen at the rising portion of the vibration waveform for each beat, the second peak is b.
In this way, it is possible to determine whether winding is appropriate by comparing the polarities of the first peak and the second peak.
[0031]
In the present embodiment, the peak value of the peak is calculated as the height up to the peak with the point that is the reference of the peak value as the rising start point, but the method of calculating the peak is arbitrary as long as it does not contradict the gist of the present invention. is there. The peak detection method is also arbitrary. In the present embodiment, the ratio between the peak height of the first peak and the peak height of the second peak is used, but other comparison methods (for example, using a difference) can also be used.
[0032]
【The invention's effect】
As described above, according to the present invention, whether or not the cuff winding state used for the measurement is appropriate regardless of the cuff size by detecting the shape of the pulse wave that is characteristically detected at the time of winding failure. Can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a sphygmomanometer according to an embodiment of the present invention.
FIG. 2 is a diagram showing a configuration example of a cuff belt according to an embodiment of the present invention.
FIG. 3 is a longitudinal sectional view showing a state where the cuff belt according to the embodiment of the present invention is wound around the upper arm of a subject.
FIG. 4 shows an example of a vibration waveform detected by a pressure sensor 16;
FIG. 5 shows an example of a vibration waveform detected by a pressure sensor 16;
FIG. 6 is a block diagram of a portion for determining systolic blood pressure according to the present embodiment.
FIG. 7 is a flowchart for explaining the operation of the blood pressure monitor according to the present embodiment.
FIG. 8 is a diagram illustrating a change in pressure of the measurement cuff 12 when the cuff winding according to the present embodiment is appropriate.
FIG. 9 is a diagram showing a change in pressure of the measurement cuff 12 when the cuff winding of the second embodiment is too loose.
[Explanation of symbols]
10 cuff belt 11 compression cuff 12 measurement cuff 13 arterial compression part 14 capillary 15 sachet 16 pressure sensor 20 measurement part 21 pressure increase part 22 pressure reduction part 23 pressure measurement part 24 control part 25 display part

Claims (5)

A measurement cuff that measures the vibration of the compression cuff and the arterial wall compressing the blood pressure measurement site, based on a change in the vibration of the arterial wall due to the change of the cuff pressure, an electronic sphygmomanometer for measuring blood pressure, said a peak detection means for detecting a peak from the vibration signal by the measuring cuff, using the detected signal possess a state determining means wound determining the winding state of the cuff by said peak detecting means, the winding state determining means Determining that the cuff winding is not appropriate when observing the peak of the pulse wave observed at the proper winding and the peak having the opposite polarity from the plurality of peaks detected by the peak detection means Electronic blood pressure monitor characterized by. The electronic sphygmomanometer according to claim 1, wherein the measurement cuff measures the vibration of the arterial wall at an arbitrary position from the approximate center of the compression cuff to the downstream end in the blood flow direction. The electronic sphygmomanometer according to claim 1, wherein the measurement cuff measures the vibration of the artery wall at a substantially central position of the compression cuff. The electronic sphygmomanometer according to claim 1, wherein the measurement cuff measures the vibration of the artery wall in the vicinity of the position of the artery that is closed by the pressure in the vicinity of the maximum blood pressure of the compression cuff. The sphygmomanometer according to any one of claims 1 to 4, wherein the winding state determination unit includes a notification unit that notifies a determination result.

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