JP2000107139A - Continuous hemomanometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent effect of noise from a power source in a continuous hemomanometer for measuring a blood pressure of a subject by vibrating a blood vessel to analyze vibration transmitted through the blood vessel. SOLUTION: This apparatus is provided with a vibrator 102 which is mounted on a subject 101 to vibrate a blood vessel by a signal from an oscillator 103, aa vibration sensor 104 to detect vibration propagated through the blood vessel and a processor 107 which detects the phase of a signal from the vibration sensor to calculate changes in the phase. A control is performed so that the oscillation frequency of the oscillator 103 gives a frequency other than an avoiding frequency with respect to a frequency, an integer multiple of a power source frequency, from a frequency minus the band width of a phase detection filter to that plus the band width of the phase detection filter in a processor 107.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for continuously measuring blood pressure by applying weak vibration to a blood vessel in a living body, detecting and analyzing the vibration propagated in the blood vessel in the field of medical instruments. About.

[0002]

2. Description of the Related Art Conventionally, for this type of continuous sphygmomanometer, a method for continuously measuring blood pressure non-invasively has been proposed, for example, as disclosed in Japanese Patent Application Publication No. 9-506024. This method focuses on the fact that the elasticity of a blood vessel changes in response to a change in blood pressure, and furthermore, the elasticity change of a blood vessel changes the propagation speed of the vibration transmitted through the blood vessel, so that the speed of the vibration propagating through the blood vessel is detected. To estimate the blood pressure.

[0003] This blood pressure measurement method will be described in more detail with reference to FIG. An exciter 102 attached to the forearm of the subject 101 vibrates the radial artery inside the forearm at a frequency f. Oscillator 103 generates frequency f, which ranges from approximately 100 Hz to 2000 Hz. Vibration sensor 104 also attached to the forearm of subject 101
Detects vibration transmitted through the radial artery and converts it into an electric signal. The electric signal from the vibration sensor 104 is
After being amplified by 5, the signal is converted into a digital signal by the A / D converter 106 and input to the processor 107. The processor 107 performs a phase detection process and calculates a phase change as viewed from the center of the arc distribution. This phase change is a change in vibration propagation speed, and corresponds to a change in blood pressure. The amount of change is used for the calibration cuff 108 and the cuff-type blood pressure monitor 10 attached to another position of the same subject 101.
The blood pressure is continuously calculated by calibrating with the measured values of the systolic blood pressure and the diastolic blood pressure according to No. 9, and the waveform is displayed on the display unit 110. Although the connection is not shown, the DC power supply 111 generates a constant DC voltage necessary for the operation of each block from an AC power supply from a power outlet 112 and supplies it to each block.

[0004]

In order to detect blood pressure with high accuracy in the above-mentioned method, it is important to detect a weak vibration transmitted through a blood vessel with high sensitivity. The signal from the vibration sensor 104 is output to the amplifier 1 without operating the vibrator 103.
FIG. 4 shows the power spectrum of the signal amplified at 05 and converted to digital data by the A / D converter 106. This indicates the noise spectrum of the system. The frequency component in the region b is a pulse wave component of the subject. As shown in FIG. 4, the noise power is strong at a frequency that is an integral multiple of the power supply frequency fs. Here, fs is the frequency of the AC power supplied to the power supply 111, for example, 50 Hz in eastern Japan and 60 Hz in western Japan.
It is. In these, the fundamental wave and harmonics of the AC power supply are mixed as noise into the input system of the apparatus via the power supply 111 or the subject, and significantly deteriorate the vibration detection sensitivity.

The present invention has been made in view of the above problems, and has been made to reduce harmonic noise from an AC power supply.
It is an object of the present invention to provide a continuous blood pressure monitor capable of detecting vibration with high sensitivity.

[0006]

According to the present invention, in order to achieve the above object, a frequency other than an avoidance frequency determined from a power supply frequency and a phase detection filter band is used as an excitation frequency. The harmonic noise of the AC power supply can be removed without specially devising circuit components, circuit configuration, and the like, and a highly sensitive sphygmomanometer can be realized in a small size and at low cost.

According to a first aspect of the present invention, there is provided a vibration applying means for attaching a subject to a blood vessel to vibrate a blood vessel, a vibration detecting means for detecting a vibration transmitted through the blood vessel, and the vibration detecting means. A continuous blood pressure monitor that continuously and non-invasively measures the blood pressure of the human body by measuring the propagation velocity of vascular vibration, comprising: The vibration frequency of the vibration means is
A continuous blood pressure, which is a frequency other than the avoidance frequency from a frequency obtained by subtracting the band of the phase detection filter in the processor from a frequency which is an integral multiple of the power supply frequency and a frequency obtained by adding the band of the phase detection filter. It can shift the harmonic noise of the AC power supply to the stop band of the phase detection filter, and can detect the signal without being affected by the harmonic noise of the AC power supply.

[0010] According to a second aspect of the present invention, there is provided a vibration detecting device mounted on a subject to vibrate a blood vessel, a vibration detecting means for detecting a vibration transmitted through the blood vessel, and the vibration detecting means. A continuous blood pressure monitor that continuously and non-invasively measures the blood pressure of the human body by measuring the propagation velocity of vascular vibration, comprising: The vibration frequency of the vibration means is
A continuous blood pressure, which is a frequency other than the avoidance frequency from a frequency obtained by subtracting the band of the phase detection filter in the processor means from a frequency which is an odd multiple of the power supply frequency and a frequency obtained by adding the band of the phase detection filter. If the harmonic noise of the odd number is larger than the harmonic of the even number, and the harmonic noise of the even number is negligible, the harmonic of the odd number will be used. By selecting only the excitation frequency while avoiding only the above, a device configuration in which the frequency selection range is wider without being affected by the harmonic noise of the AC power supply becomes possible.

According to a third aspect of the present invention, there is provided an oscillator for oscillating a signal of a certain frequency, a vibrator mounted on a subject and oscillating a blood vessel by a signal from the oscillator,
A vibration sensor that is attached to the subject and detects a vibration transmitted through a blood vessel, an A / D converter that converts a signal from the vibration sensor into a digital signal, and a phase detector that detects a signal from the A / D converter And a display unit for displaying a waveform of a signal from the processor, wherein the oscillation frequency of the oscillator is set to the phase detection in the processor unit for a frequency that is an integral multiple of the power supply frequency. A continuous sphygmomanometer characterized by a frequency other than the avoidance frequency from the frequency obtained by subtracting the filter band to the frequency obtained by adding the band of the phase detection filter. It is possible to shift to the cutoff band and detect signals without being affected by the harmonic noise of the AC power supply. Without Rukoto, it is possible to inexpensively realize the sphygmomanometer sensitive small.

According to a fourth aspect of the present invention, the oscillator outputs a sine wave s having a frequency other than the avoidance frequency and a sine wave c having a phase difference of 90 degrees from the sine wave s, A processor determines the sine wave s from the oscillator and the A / D
A first multiplier for inputting and multiplying a signal from a converter; a second multiplier for inputting and multiplying a sine wave c from the oscillator and a signal from the A / D converter; The continuous sphygmomanometer according to claim 3, further comprising first and second phase detection filters that perform phase detection of an output of the multiplier, and a calculation unit that calculates a phase change from an output of each of the phase detection filters. The harmonic noise of the AC power supply can be shifted to the stop band of the phase detection filter, and the signal can be detected without being affected by the harmonic noise of the AC power supply. Special measures are taken for circuit components and circuit configuration. Without this, a highly sensitive blood pressure monitor can be realized at a small size and at low cost.

The invention according to claim 5 of the present invention is characterized in that the processing result in the processor is calibrated with the measured values of the systolic blood pressure and the diastolic blood pressure by the cuff sphygmomanometer attached to the same subject. Item 5. The continuous sphygmomanometer according to any one of items 1 to 4, wherein the harmonic noise of the AC power supply can be shifted to a stop band of the phase detection filter, and the signal is not affected by the harmonic noise of the AC power supply. Detection becomes possible, and a small and inexpensive high-sensitivity and high-precision sphygmomanometer can be realized without specially devising circuit components and circuit configuration.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. (Embodiment) The basic configuration of a continuous blood pressure monitor according to an embodiment of the present invention is the same as that of the conventional example shown in FIG. The present embodiment differs from the conventional example in the configuration and operation of the oscillator 103 and the processor 107. The embodiment of the present invention will be described below with reference to FIG. In FIG. 1, the processor includes multipliers 1 and 2, phase detection filters 3 and 4, a blood pressure calculation unit 5, and a control unit 6.

The oscillator 103 outputs a sine wave s (sin) having a frequency designated by the control unit 6 and a sine wave c (cos) having a phase shifted by 90 degrees from the sine wave s. The sine wave s is sent to the vibrator 102 and the multiplier 1
Is input to one of the inputs. The sine wave c is input to one input of the multiplier 2. The remaining input lines of the multipliers 1 and 2 are connected to the output of the A / D converter 106, and perform multiplication of the sine waves s and c and the output of the A / D converter 106, respectively. Outputs of the multipliers 1 and 2 are input to phase detection filters 3 and 4, respectively. Phase detection filter 3,
A low-pass filter 4 has the same frequency characteristics, and its cut-off characteristics are controlled by the control unit 6. The blood pressure calculation unit 5 regards the inputs from the phase detection filters 3 and 4 as complex vectors having a real component and an imaginary component, respectively, and calculates the phase change of the complex vector. The blood pressure is calculated by calibrating with the measured value of the blood pressure.

Here, the characteristics of the multipliers 1 and 2 and the phase detection filters 3 and 4 constituting the sphygmomanometer will be described. The output signal of the A / D converter 106 is frequency-shifted by multiplying the excitation frequency by the multipliers 1 and 2 so that the excitation frequency component becomes a DC component. After that, only signals around the DC component are output to the blood pressure calculation unit 5 by the phase detection filters 3 and 4. Therefore, the frequency band output to the blood pressure calculation unit 5 is the A / D converter 1
When converted to the band of the output signal of 06, (excitation frequency −
The frequency ranges from (phase detection filter cutoff frequency) to (excitation frequency + phase detection filter cutoff frequency). From the above, if the excitation frequency is appropriately selected in the above-mentioned frequency band, and the frequency band output to the blood pressure calculation unit 5 does not include the harmonic noise of the power supply, the harmonic noise of the power supply is not affected. This makes it possible to measure vibration.

From the above, the control unit 6 controls the oscillator 10
3 and the frequency characteristics of the phase detection filters 3 and 4 are controlled as follows. The control unit 6 sets the cutoff frequency of the phase detection filters 3 and 4 to fc Hz.
Usually, fc is set to about 15 Hz. However, the cutoff frequency here means a frequency at which the gain becomes -10 db. FIG. 2 shows the frequency characteristics of the phase detection filters 3 and 4 at that time. The power supply frequency here is fp Hz. The control unit 6 sets fp * n-fc ≦ f ≦ fp * n + fc, where n is a frequency that satisfies the inequality of a natural number as an avoidance frequency, and selects a frequency other than the avoidance frequency as the excitation frequency f Hz. For example, if fc = 15 Hz and fp = 50 Hz, the avoidance frequencies are 35 Hz to 65 Hz, 85 Hz to 115 Hz, 135 Hz to 1
65 Hz, 185 Hz to 215 Hz ..... The frequency range that can be set to the excitation frequency f Hz is 65 Hz to 85 Hz, 1
15 Hz to 135 Hz, 165 Hz to 185 Hz, etc.

By setting the excitation frequency to a frequency other than the above-described avoidance frequency, even if a harmonic of the power supply frequency exists as noise, the cut-off frequency band of the phase detection filters 3 and 4 is output from the multipliers 1 and 2. Therefore, the output of the phase detection filters 3 and 4 is sufficiently attenuated, and a device in which harmonics of the power supply frequency are not affected by noise can be obtained.

As described above, according to the configuration of the continuous sphygmomanometer according to the embodiment of the present invention, a highly sensitive continuous sphygmomanometer can be used without taking measures against power supply noise to the DC power supply 111 and the subject. Can be configured.

[0018]

As is apparent from the above description, according to the present invention, circuit components and circuit configurations are set by setting a frequency other than the avoidance frequency determined from the power supply frequency and the phase detection filter band as the excitation frequency. It is possible to remove the harmonic noise of the AC power supply without special measures, and to realize a highly sensitive and accurate blood pressure monitor in a small size and at a low cost.

[Brief description of the drawings]

FIG. 1 is a detailed block diagram of a vibrator and a processor of a sphygmomanometer according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing frequency characteristics of a phase detection filter of the sphygmomanometer according to the embodiment.

FIG. 3 is a schematic block diagram of a sphygmomanometer common to the embodiment and the conventional example.

FIG. 4 is a characteristic diagram illustrating a noise spectrum input to the embodiment and the conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Multiplier 2 Multiplier 3 Phase detection filter 4 Phase detection filter 5 Blood pressure calculation unit 6 Control unit 101 Subject 102 Exciter 103 Transmitter 104 Vibration sensor 105 Amplifier 106 A / D converter 107 Processor 108 Cuff 109 Cuff type blood pressure Measuring instrument 110 Display section 111 DC power supply 112 Power outlet

Claims (5)

[Claims] A vibrating means mounted on a subject for vibrating a blood vessel; a vibration detecting means for detecting a vibration transmitted through the blood vessel; and a phase detector for detecting an electric signal from the vibration detecting means to detect a phase. With a processor means for analyzing the change, in a continuous blood pressure monitor continuously and non-invasively measure the blood pressure of the human body by measuring the propagation speed of the vascular vibration, the excitation frequency of the excitation means, A continuous blood pressure, which is a frequency other than the avoidance frequency from a frequency obtained by subtracting the band of the phase detection filter in the processor from a frequency which is an integral multiple of the power supply frequency and a frequency obtained by adding the band of the phase detection filter. Total. 2. Vibration means for attaching a subject to vibrate a blood vessel, vibration detecting means for detecting a vibration transmitted through the blood vessel, and detecting a phase of an electric signal from the vibration detecting means by performing phase detection. With a processor means for analyzing the change, in a continuous blood pressure monitor continuously and non-invasively measure the blood pressure of the human body by measuring the propagation speed of the vascular vibration, the excitation frequency of the excitation means, A continuous blood pressure, which is a frequency other than the avoidance frequency from a frequency obtained by subtracting the band of the phase detection filter in the processor means from a frequency which is an odd multiple of the power supply frequency and a frequency obtained by adding the band of the phase detection filter. Total. 3. An oscillator for oscillating a signal of a certain frequency;
A vibrator attached to the subject to vibrate a blood vessel by a signal from the oscillator, a vibration sensor attached to the subject to detect a vibration transmitted through the blood vessel, and a signal from the vibration sensor to a digital signal An A / D converter for conversion;
A processor for detecting a phase of the signal from the A / D converter to calculate a change in phase; and a display unit for displaying a waveform of the signal from the processor, wherein the oscillation frequency of the oscillator is an integer of a power supply frequency. A continuous sphygmomanometer wherein the frequency is a frequency other than the avoidance frequency from the frequency obtained by subtracting the band of the phase detection filter in the processor means to the doubled frequency, from the frequency obtained by adding the band of the phase detection filter. 4. An oscillator outputs a sine wave s having a frequency other than the avoidance frequency and a sine wave c out of phase with the sine wave s by 90 degrees, and the processor outputs a sine wave s from the oscillator. Multiplier for inputting and multiplying a signal from the A / D converter and a second multiplier for inputting and multiplying a sine wave c from the oscillator and a signal from the A / D converter 4. The continuous blood pressure system according to claim 3, comprising: a first and a second phase detection filter for phase-detecting an output of each of said multipliers; and a calculating unit for calculating a phase change from an output of each of said phase-detection filters. Total. 5. The method according to claim 1, wherein the processing result in the processor is calibrated by the measured values of the systolic blood pressure and the diastolic blood pressure by the cuff type sphygmomanometer attached to the same subject. Continuous sphygmomanometer.