JP5798226B2 - Pulse wave analyzer - Google Patents

Description

  The present invention relates to a pulse wave analyzing apparatus that analyzes a frequency component including a Korotkoff sound and generates a spectrogram corresponding to a compressed pulse wave.

  Conventionally, a subject's pulse wave is used for blood pressure measurement and the like. As a method of measuring blood pressure based on the pulse wave, Korotkoff sounds generated when the cuff pressure is gradually reduced after the cuff is attached to the upper arm and then the blood vessel is compressed with the cuff pressure generated by the air supplied to the cuff. There is known an auscultation method in which the pressure at the time of generating the Korotkoff sound is measured as the maximum blood pressure and the pressure at the time of the disappearance of the Korotkoff sound is measured as the minimum blood pressure.

  Similarly to the auscultation method described above, when the artery is compressed with cuff pressure, the vibration phenomenon of the cuff internal pressure caused by the pulsation of the artery is detected by the pressure sensor. An oscillometric method is also known that detects when the blood pressure has occurred as a minimum blood pressure.

  However, in the auscultation method and the oscillometry method, individual differences are likely to occur in the measurement results due to the experience and the habits of the doctors and nurses to be measured, and skill is required to accurately measure the blood pressure.

  As a countermeasure for this, for example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2010-17299), a strain sensor is inserted between the upper arm of the subject and a cuff attached to the upper arm, and a pressure pulse wave is compressed by the strain sensor. A technique for measuring and measuring systolic blood pressure and diastolic blood pressure from the occurrence and disappearance of protrusions appearing in the compressed pulse wave is disclosed. According to this technique, the pressure (beat) from the blood vessel can be accurately detected as distortion.

JP 2010-17299 A

  Although Patent Document 1 describes detecting the occurrence and disappearance of protrusions appearing in a compressed pulse wave measured by a strain sensor, it is not sufficient as a method for determining the occurrence and disappearance of Korotkoff sounds. It was.

  Accordingly, an object of the present invention is to provide a pulse wave analysis device that can determine the occurrence and disappearance of Korotkoff sound based on the compressed pulse wave measured by a strain sensor and obtain the maximum blood pressure and the minimum blood pressure. It is to provide.

  In order to achieve the above object, the present invention provides a cuff attached to a portion to be examined through which a living artery of a subject passes, a pressure-increasing / decreasing means for increasing / decreasing the cuff, and the subject to which the cuff and the cuff are attached. A pressure pulse wave detecting means comprising a strain sensor for detecting a pressure pulse wave interposed between the person to be inspected, and when the pressure is reduced after pressurizing the cuff with the pressure increasing / decreasing means, A spectrogram for generating a spectrogram corresponding to the compressed pulse wave by analyzing the frequency component including the Korotkoff sound from the time-series data of the compressed pulse wave detected by the compressed pulse wave detecting means by short-time fast Fourier transform The center position of one pulse wave is determined from the generation means and the time series data of the compressed pulse wave, the energy in the frequency band specific to the Korotkoff sound is extracted from each frequency characteristic in the one pulse wave, and the energy Based on Provided is a pulse wave analyzing apparatus comprising: means for detecting occurrence and disappearance of a Tokoku sound and determining a systolic blood pressure and a diastolic blood pressure; and a display means for displaying the systolic blood pressure and the diastolic blood pressure. Is.

In a preferred aspect of the present invention, the means for determining the systolic blood pressure and the diastolic blood pressure is a sum of frequency bands specific to Korotkoff sounds set within a range of 10 to 100 Hz from each frequency characteristic in one pulse wave. The energy RMS is calculated based on the following formula, and the blood pressure when the RMS first exceeds a preset threshold value is set as the maximum blood pressure, and then the blood pressure when the RMS first falls below the threshold value is set as the maximum blood pressure. Determined as minimum blood pressure.

  Here, Xi is the sound energy level of each frequency within the frequency band including the Korotkoff sound extracted from the frequency analysis result of each pulse wave, and n is the number of Xi.

  According to the present invention, when the pressure is reduced after the cuff is pressurized by the pressurizing and depressurizing means, the frequency component including the Korotkoff sound is obtained from the time-series data of the compressed pulse wave detected by the compressed pulse wave detecting means including the strain sensor. Analyzed by a short-time fast Fourier transform, the center position of one pulse wave is determined from the time-series data of the compressed pulse wave, and the energy in the frequency band specific to the Korotkoff sound is determined from the frequency characteristics within one pulse wave. Extraction and detection of the occurrence and disappearance of Korotkoff sounds based on the energy to determine the systolic blood pressure and the minimum blood pressure. Therefore, the occurrence and disappearance of Korotkoff sounds are accurately detected to detect the systolic blood pressure and the minimum blood pressure. Blood pressure can be determined.

It is a block diagram of the pulse wave analyzer by 1st Embodiment. It is a system block diagram of a pulse wave analysis device. 3 is a flowchart showing a flow of pulse wave analysis. It is explanatory drawing of the screen which displays a pulse wave analysis result similarly. It is explanatory drawing of the color showing the intensity | strength (amplitude) of a frequency similarly. It is a block diagram of the pulse wave analyzer by 2nd Embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[First Embodiment]
1 to 5 show a first embodiment of the present invention. As shown in FIG. 1, the pulse wave analysis device according to the present embodiment includes a cuff unit 1, a pump unit 2, and a computer terminal device (hereinafter simply referred to as “terminal device”) 3.

  As shown in FIG. 2, the cuff unit 1 includes a cuff band 6 that is a representative of a cuff that is wound around and mounted on an upper arm that is a portion to be inspected through a living artery, and a strain sensor 7 that serves as a pressure pulse wave detection unit. Have. The cuff belt 6 has an air bag that compresses the upper arm, and this air bag is communicated with the pressurizing / depressurizing means 8 provided in the pump unit 2 described later via an air tube 10. The strain sensor 7 is disposed inside the cuff band 6 and is interposed between the cuff band 6 and the upper arm by wrapping the cuff band 6 around the upper arm of the subject. Pressed against the upper arm. Then, the pressure pulse wave to be detected is detected from the vibrations that occur when the blood vessels of the subject are compressed by tightening the cuff band 6.

  Further, the pump unit 2 is provided with pressure increasing / decreasing means 8 and a pressure sensor 9. The pressurizing / depressurizing means 8 has a pressurizing pump and an exhaust valve, and the pressurizing pump supplies air to an air bag provided in the cuff belt 6 to inflate the air bag. The exhaust valve adjusts the pressure supplied to the cuff belt 6 side (hereinafter referred to as “cuff pressure”) according to the drive signal from the terminal device 3 and exhausts the air supplied to the air bag. Shrink the air bag. The pressure sensor 9 is connected to the air tube 10, detects the cuff pressure supplied to the air bag via the air tube 10, and transmits data of the detected cuff pressure to the terminal device 3.

  FIG. 1 shows a notebook personal computer as an example of the terminal device 3. The terminal device 3 includes an input unit 3a including a keyboard and the like, and a display unit 3b as a display unit such as a liquid crystal monitor, and an arithmetic processing unit 3c is accommodated therein. The input unit 3a includes a mouse. The arithmetic processing unit 3c is mainly composed of a microcomputer having a CPU, ROM, RAM, HDD (hard disk drive), SDD (silicon disk drive), etc., and ROM, HDD (hard disk drive) and / or SDD (silicon). The arithmetic processing is performed by the CPU in accordance with a program stored in the disk drive.

  The arithmetic processing unit 3c controls the operation of the pressurizing pump based on the cuff pressure detected by the pressure sensor 9, and also controls the opening / closing operation of the exhaust valve. Further, the arithmetic processing unit 3c analyzes the compressed pulse wave detected by the strain sensor 7, calculates the maximum blood pressure and the minimum blood pressure, and calculates the heart rate from the average of the intervals of one pulse wave. For example, the pulse interval is obtained by geometrically averaging the intervals of each pulse wave from the time of the highest blood pressure to the time of the lowest blood pressure, and the heart rate is calculated by dividing 1 minute by that time. Further, the arithmetic processing unit 3c includes spectrogram generating means (so-called sonogram or sonagram) for generating a spectrogram Sp for each pulse wave in time series from the frequency analysis of the compressed pulse wave. Then, these calculation results are output to the display unit 3b and displayed. The output of the strain sensor 7 is converted into a digital signal by an amplifier and an A / D converter mounted on the pump unit 2 and sent to the terminal device 3.

  FIG. 4 shows a display example of the display unit 3b. In the lower part of the display unit 3b, display windows such as a systolic blood pressure display unit 11, a diastolic blood pressure display unit 12, and a pulse rate display unit 13 are provided. Further, a pulse waveform display unit 14 is provided above the spectrogram display unit 15, and a spectrogram display unit 15 is formed thereabove. Furthermore, a blood flow pattern display unit 16 is provided at the top of the display unit 3b.

  The spectrogram display unit 15 represents the frequency on the vertical axis and the time on the horizontal axis, analyzes the frequency component of the pulse wave, and displays the intensity (amplitude) of the specific frequency as a gradation in brightness or color (spectrogram drawing). Based on this, the result processed by the arithmetic processing unit 3c is displayed as a spectrogram Sp. The blood flow pattern display unit 16 displays a power level (KSG) pattern (blood flow pattern) in the frequency range for detecting Korotkoff sounds for each pulse wave.

  Next, the flow of pulse wave analysis executed by the arithmetic processing unit 3c described above will be described with reference to the flowchart shown in FIG.

  When the terminal device 3 is turned on, the CPU provided in the arithmetic processing unit 3c reads the pulse wave analysis program stored in the ROM, HDD (hard disk drive) and / or SDD (silicon disk drive), and initializes the system. Then, the pulse wave analysis processing routine is set in a standby state.

  On the other hand, when executing the pulse wave analysis process, first, the cuff band 6 is wound around the upper arm of the subject in a predetermined manner. Next, a pulse wave analysis processing routine is started by operating a keyboard, a mouse, or the like provided in the input unit 3a of the terminal device 3.

  Then, a pressurization process is first started by step S1. In this pressurizing step, the exhaust valve provided in the pressurizing and depressurizing means 8 is closed and the pressurizing pump is operated to supply air to the air bag built in the cuff belt 6. Inflate the bag. As a result, the upper arm of the subject is tightened by the cuff belt 6 and the internal pressure of the air bag is relatively increased. The arithmetic processing unit 3c monitors based on the cuff pressure data detected by the pressure sensor 9 until the cuff pressure reaches a predetermined pressure sufficient for measuring the maximum blood pressure. Then, when the cuff pressure reaches a predetermined pressure sufficient for measuring the maximum blood pressure, the operation of the pressurizing pump is stopped.

  Next, the compressed pulse wave measurement step is executed in steps S2 and S3. In step S2, the exhaust valve is opened to start reducing the cuff pressure. Next, in step S3, the cuff pressure data detected by the pressure sensor 9 and the compressed pulse wave data detected by the strain sensor 7 are captured. When the exhaust valve is opened, the air pressure in the air bag is gradually reduced, and the cuff pressure detected by the pressure sensor 9 is substantially linear while detecting the pulse wave as shown in the cuff pressure waveform P1 shown in FIG. Decrease.

  Then, a frequency analysis display process is performed by step S4. In this frequency analysis display step, the time series data of the compressed pulse wave detected by the strain sensor 7 is designated with a certain time width (time width for performing short-time fast Fourier transform, that is, short-time FFT), and shorter than this time width. While moving at intervals, frequency analysis by short-time FFT is performed. Then, the result of the frequency analysis is drawn on the spectrogram display unit 15 of the display unit 3b in accordance with the time series. As shown in FIG. 4, the spectrogram Sp is drawn on the spectrogram display unit 15 as time-series changes of frequency components corresponding to pulse waves, with the vertical axis representing frequency and the horizontal axis representing time.

  In the present embodiment, the intensity (amplitude) of the frequency component of the time-series data of the compressed pulse wave is displayed in gradation in color, and as shown in FIG. The strong intensity is set to white, and the saturation is gradually set to become lower, for example, blue, light blue, pink, orange, and green as the intensity shifts from weaker to stronger. Incidentally, the spectrogram Sp drawn on the spectrogram display unit 15 shown in FIG. 4 is displayed with the lowest frequency and the highest intensity in the vicinity of the center of the pulse in white, and conversely, the higher the frequency and the outward the purple color. A pattern (pattern) displaying the lowest intensity is formed.

Next, a blood pressure determination step is executed in steps S5-11. In this step, first, in step S5, the center position of one pulse wave is determined from the time-series data of the compressed pulse wave detected by the strain sensor 7. Specifically, each frequency characteristic in one pulse wave is extracted so that the + peak position of the time-series data of the compressed pulse wave is centered. Then, in step S6, in order to identify the arterial squeezing waveform of the compressed pulse wave corresponding to the Korotkoff sound from each frequency characteristic in the extracted one pulse wave, the energy of the frequency band specific to the Korotkoff sound is set to each frequency characteristic. Extract from each. Specifically, as the frequency band specific to the Korotkoff sound, the total RMS of energy in the band of 10 to 100 [Hz] (preferably 17 to 30 [Hz]) in the frequency analysis result is obtained from the following equation. calculate. Then, the largest RMS of the energy in the frequency band specific to the Kolkov sound is extracted as KSG in each pulse wave.

  Here, Xi is the sound energy level of each frequency within the frequency band including the Korotkoff sound extracted from the frequency analysis result of each pulse wave, and n is the number of Xi.

  Then, the process proceeds to step S7, and it is checked whether or not the occurrence of Korotkoff sound has been detected based on the RMS obtained by Equation 1. That is, when the change in RMS for each pulse wave is examined, it has been clarified from experiments that Korotkoff sounds are generated in a range where the RMS value is large. Therefore, in this step, if the first pulse wave whose RMS changes greatly is detected, the process proceeds to step S8. If not detected, the process proceeds to step S9. In this step, a value lower by a predetermined level statistically obtained from the maximum RMS value of each pulse wave is set as a threshold value. When an RMS exceeding the threshold value is detected for the first time, the pulse is detected. You may make it set a wave as the head of Korotkoff sound generation.

  When it is determined that the first pulse wave in which the RMS greatly changes is detected and the process proceeds to step S8, the systolic blood pressure is determined. That is, in the above-described step S7, when the first pulse wave with a large change in RMS is detected, this is the head of the Korotkoff sound generation, so the middle between the pulse wave and the pulse wave immediately before is the systolic blood pressure point P2. Thus, the cuff pressure P1 detected by the pressure sensor 9 at the detection time is determined as the maximum blood pressure P4 (see FIG. 4), and the process proceeds to step S9.

  In step S9, the process proceeds to step S3 before the Korotkoff sound is generated, and after the Korotkoff sound is generated, that is, after passing through Step S8 once, it is checked whether or not the disappearance of the Korotkoff sound is detected based on the RMS obtained by the equation 1. . That is, when the change in RMS for each pulse wave is examined, it is clear from experiments that contrary to the above, the Korotkoff sound disappears at the point where the RMS suddenly decreases. Therefore, in this step, if the first pulse wave in which the RMS has rapidly decreased is detected, it is determined that it has disappeared, and the process proceeds to step S10. On the other hand, if the first pulse wave in which the RMS has rapidly decreased is not detected, the process returns to step S3 and new data is captured.

  In step S10, the minimum blood pressure is determined. That is, when the first pulse wave in which the RMS is greatly reduced is detected in step S9 described above, this is the end of the Korotkoff sound generation, so the middle between the pulse wave and the pulse wave immediately before is the lowest blood pressure point P3. Thus, the cuff pressure waveform P1 detected by the pressure sensor 9 at the detection time is determined as the minimum blood pressure P5 (see FIG. 4), and the process proceeds to step S11. In this case, a value lower than a certain level statistically obtained from the maximum RMS value of each pulse wave is set as a threshold value, and the pulse wave when the pulse wave first falls below this threshold value is the pulse wave at the end of the Korotkoff sound. You may make it set as.

  When the process proceeds to step S11, the heart rate is calculated from the average of the intervals of one pulse wave, and the process proceeds to step S12. In this case, the pulse rate per unit may be calculated based on the number of each pulse wave extracted between the systolic blood pressure point P2 and the diastolic blood pressure point P3 and the measurement time. Alternatively, the pulse interval may be obtained by geometrically averaging the intervals of the respective pulse waves from the maximum blood pressure point P2 to the minimum blood pressure point P3, and 1 minute may be divided into the time to obtain the pulse rate.

  In step S12, the blood pressure and pulse rate display step is executed, and the RMS for each pulse wave calculated in step S6, that is, KSG, the maximum blood pressure determined in step S8, the minimum blood pressure determined in step S10, and the calculation in step S11. The displayed pulse rates are respectively displayed on the blood flow pattern display unit 16, the systolic blood pressure display unit 11, the diastolic blood pressure display unit 12, and the pulse rate display unit 13 of the display unit 3b, and the routine is terminated. In this case, it is also possible to print out the contents displayed on the display unit 3b or numerical data by connecting a printer to the terminal device 3. Furthermore, by connecting this terminal device 3 to a communication line such as the Internet, it is possible to transmit the data calculated this time to other terminal devices and use them for various analyzes in other terminal devices. .

  As described above, according to the present embodiment, the hemodynamics (maximum blood pressure, minimum blood pressure, pulse rate, spectrogram Sp of frequency analysis, blood analysis obtained based on the pressure pulse wave detected from the subject is displayed on the display unit 3b. Flow pattern) is displayed, the index related to the hemodynamics can be visually grasped, diagnosis is easy, and user-friendliness is good.

  Moreover, the physical condition (anemia, hypotension, arteriosclerosis, arrhythmia, heart disease, etc.) of the subject can be easily grasped from the pattern (pattern) of the spectrogram Sp of the frequency analysis.

[Second Embodiment]
FIG. 6 shows a second embodiment of the present invention. In the first embodiment described above, a general-purpose personal computer is used as the terminal device 3, but in this embodiment, the terminal device 3 is dedicated. Therefore, the pump unit 2 shown in the first embodiment is built in the terminal device 3. Note that the display content of the display unit 3b and the arithmetic processing executed by the arithmetic processing unit 3c are the same as those in the first embodiment, and thus description thereof is omitted.

  In the present embodiment, since the terminal device 3 is dedicated, the entire system can be reduced in size.

  The present invention is not limited to the above-described embodiment. For example, an acoustic sensor such as a microphone may be used in place of the strain sensor 7, and the compressed pulse wave may be detected by the acoustic sensor.

DESCRIPTION OF SYMBOLS 1 ... Cuff unit 2 ... Pump unit 3 ... Terminal device 3b ... Display part 3c ... Arithmetic processing part 6 ... Cuff belt 7 ... Strain sensor 8 ... Pressure increasing / decreasing means 9 ... Pressure sensor 15 ... Spectrogram display part P1 ... Cuff pressure waveform P2 ... Systolic blood pressure P3 ... systolic blood pressure P4 ... systolic blood pressure P5 ... systolic blood pressure Sp ... spectrogram

Claims (2)

A cuff attached to a part to be inspected through which a subject's living artery passes,
Pressurizing / depressurizing means for increasing / decreasing the cuff;
A compressed pulse wave detecting means comprising a strain sensor, which detects the compressed pulse wave interposed between the cuff and the inspected portion of the subject to which the cuff is attached;
When the cuff is pressurized by the pressurizing and depressurizing means and then depressurized, a frequency component including Korotkoff sound is quickly extracted from the time series data of the compressed pulse wave detected by the compressed pulse wave detecting means by fast Fourier transform. A spectrogram generating means for analyzing and generating a spectrogram corresponding to the compressed pulse wave;
In order to identify the arterial squeezing waveform of the compressed pulse wave corresponding to the Korotkoff sound from each frequency characteristic in one pulse wave, one pulse so that the + peak position is centered from the time-series data of the compressed pulse wave. Determine the center position of the wave, calculate the RMS of energy in the frequency band specific to Korotkoff sounds from the frequency analysis by short-time fast Fourier transform in one pulse wave, and the RMS is preset. Means for determining the highest blood pressure and the lowest blood pressure with the blood pressure when the first threshold value is exceeded as the highest blood pressure, and the blood pressure when the RMS first falls below the threshold value as the lowest blood pressure;
A pulse wave analysis device comprising: display means for displaying the maximum blood pressure and the minimum blood pressure.
(Where Xi is the sound energy level of each frequency within the frequency band extracted from the frequency analysis result of each pulse wave, and n is the number of Xi.) The pulse wave analyzer according to claim 1, wherein a frequency band specific to the Korotkoff sound is 10 to 100 Hz.