JPH08336508A - Detection of respiration - Google Patents

Abstract

PURPOSE: To measure the period of respiration without feeling abnormality due to addition or trammels as performing an ordinary office job by detecting a sound or motion generated from the heart and taking out the information of respiration from the information of the envelope of a synchronized signal. CONSTITUTION: This method is equipped with a detector 1 consisting of an acceleration sensor which detects the sound or motion generated from the heart. The detector is loaded on one or more points on a body, and a signal on one side from the detector 1 is inputted to a heartbeat measuring part 2 and the one on the other side to a respiration measuring part 3. The respiration measuring part 3 finds out two maximum values that exist at an interval of around one second by a peak detecting part 4. Thence, a curve is obtained by using the height and time of a peak, for example, linear interpolation by a linear interpolation part 9. After such processing is completed, second data with respect to a heartbeat is substituted for first data with respect to the heartbeat, and the second data with respect to the heartbeat is found again. The curve of respiration is found by repeating such measurement.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a detection method capable of measuring respiration by a heart rate meter using an acceleration sensor.

[0002]

2. Description of the Related Art Recently, due to computerization of work and complication of operations, stress has been generated on human beings, causing problems. Therefore, studies have been conducted to measure the stress accumulated in humans and to feed back to the environment. As one of the parameters for the measurement, changes in heartbeat and respiratory cycle have been noted. Conventionally, an electrocardiogram is generally used to measure a heartbeat, and it is widely used because stable data can be obtained. However, this method
Since the electrodes must be attached on the body surface and a cable for measurement is required, a posture and environment for measurement are required. Not suitable.

Therefore, the present applicant has previously proposed a heart rate monitor using an acceleration detector. This heart rate monitor is 1 cm x 2
It is possible to use by fixing a small acceleration detector of about cm x 0.5 cm to a point on the body and wirelessly transmitting the acceleration of this portion to a measuring machine. Detecting the acceleration is to detect the vibration of the body caused by the movement of the valve of the heart, etc., which has the drawback of being greatly affected by the movement of the human body, vocalization, etc. On the other hand, the detector is small, Being wireless, it has the advantage of being very easy to use.

On the other hand, breathing is detected by putting a breathing belt around the chest and obtaining a breathing curve by stretching the breathing belt, or by attaching a mask-like object and measuring directly from the breathing (Majima Hidenobu "Sogaku" ( Bunkodo)), like the electrocardiogram, there is a problem that you can not measure while attending to normal work.

As an attempt to measure respiration using an acceleration sensor, for example, the one described in Japanese Patent Laid-Open No. 02-163283 is known. This is because the accelerometer is attached to the surface of the living body that reciprocates in relation to respiration, and the respiration of the living body is detected based on the signal output from the acceleration sensor, so that it is not affected by the mounting state of the sensor part. , Accurately detect breathing. The surface of the upper abdomen reciprocates in association with breathing, the leaf spring of the acceleration sensor is distorted due to the reciprocal movement of the surface, and the strain of the leaf spring is detected by the semiconductor strain gauge. The acceleration sensor outputs a signal corresponding to the reciprocal movement of the surface of the upper abdomen of the subject. Respiration is detected based on the signal supplied from the acceleration sensor, and the respiratory rate and respiratory waveform per unit time are computed by CT.
It is displayed on a display device such as an R display device. However, the body does not move only by breathing, but other movements are predominant. Therefore, the signal coming out of the detector is the movement of the body, and the movement caused by respiration is buried in it as a very small signal. There is a drawback that breathing cannot be taken out accurately.

There is also one that measures both heartbeat and respiration (Japanese Patent Laid-Open No. 03-4834). This is because by installing a required number of sound sensors for measurement in a position where the bather's biofunction sound propagates using hot water in the bathtub as a medium, and connecting an electrical output device that displays the biofunction sound to the sensor, Make it easy to measure biological function sounds while taking a bath. When a bather enters the bathtub, the biological function sound reaches the sound sensor for measurement from the human body through the hot and cold water in the bathtub.By processing the output signal of the sound sensor for measurement, heart sounds and pulmonary breathing sounds are processed. It is possible to measure such things naturally without labor. Above all, this method has a drawback that it cannot be measured unless it is put in a bathtub, so that it is impossible to perform measurement while working in an office as described here.

[0007]

The present invention has been made in view of the above problems, and its object is to:
It measures the cycle of breathing without feeling strangeness due to addition or restraint while performing normal office work, especially
An object of the present invention is to provide an extraction method by which a respiratory signal can be obtained from the signal of the accelerometer.

[0008]

In order to achieve the above object, a respiration detecting method according to a first aspect of the present invention includes a detector for detecting a sound or a motion generated by the heart at one or more points on the body. Envelope of the periodic signal by wearing it, examining the output signal from the detector corresponding to one or more cycles of the heart, and performing processing to connect a plurality of maximum values and / or minimum values of the initial signal emitted by the heart. The feature is that line information is created and respiration information is extracted from this envelope information.

[0009]

The present inventors attach the detectors to one or more points on the body and detect the sound or movement generated by the heart,
It was discovered that the amplitude of the pulsed waveform train was changed in the same cycle as breathing. FIG. 3 shows an example of an acceleration heartbeat signal, and FIG. 4 shows an example of a breathing curve when the heartbeat is measured. This breathing curve is obtained by stretching a belt around the chest by a conventional method. As is clear from comparing both the heartbeat and the respiration curve, the amplitude of the heartbeat signal is modulated in the opposite phase of the respiration curve. The cause is considered as follows. When the heart valve or the like is closed, a step-like movement is generated, which is transmitted through the body and reaches the detector 1 to form an impulse response-like waveform. Adjacent waveforms have the same valve closure but different waveforms due to the effects of respiration, which changes the damping characteristics of the organ from the heart to the detector, which in turn causes vibrations of the organ. It is considered that there was a change in the state of attenuation of the sound. Therefore, we devised a method to detect respiration from the heartbeat signal sequence using this fact. That is, in the present invention, a detector for detecting the sound or motion generated by the heart is
Wear on one or more points on the body. As an output signal of the detector, a signal of one or more cycles of the heart is examined, and by processing such that a plurality of maximum values or minimum values of the initial signal emitted by the heart are connected, the information of the envelope of the cycle signal is obtained. Create and extract breathing information from this envelope information.

[0010]

An embodiment of the present invention will be described below.
FIG. 1 is a schematic configuration diagram of a block diagram of a system capable of implementing the respiratory detection method according to the embodiment, FIG. 2 is a flowchart of a maximum value calculation process executed as initialization in the system, and FIG. 3 is detected in the system. FIG. 4 is a graph showing a detector signal, FIG. 4 is a graph showing a respiration curve obtained by a conventional method, and FIG. 5 is a graph showing a respiration curve obtained using the same system.

In FIG. 1, the present system is provided with a detector 1 which is an acceleration sensor for detecting a sound or movement generated by the heart. The detector 1 is attached to one or more points on the body. The signal from the detector 1 is divided into two, one is input to the heartbeat measuring unit 2 and the other is input to the respiration measuring unit 3. The heartbeat measuring section 2 may be a conventionally known one that measures a heartbeat using a signal from a conventionally known acceleration sensor. For example, those described in “R & D of human sensation measurement application technology in 1993” commissioned research result report, second edition, R & D of physiological effect measurement technology, page 529, etc. can be adopted.

In the respiration measuring unit 3, first, the peak detecting unit 4 roughly checks the intervals of heartbeats by a routine for finding a simple maximum value as shown in the flow chart of FIG. Unless there is a special environment, the normal heart rate is about 1 to 2 beats per second, so the data of about 1 second is first stored in the memory, and the maximum routine is used.
Find the two maximums that are close to one second apart. The one that is earlier in time will be called the maximum value of the first heartbeat, and the one that is later in time will be called the maximum value of the second heartbeat. At this time, the maximum value is stored in the memory 5, and this value is used as a threshold value for obtaining a peak in the subsequent search performed in real time.

It is known that there are roughly two large vibrations in one cycle of the heart. Strictly more, but
Since the amplitude is small and the noise is large, it is difficult to detect this. Therefore, two typical ones will be described here. The vibration caused by the closure of the tricuspid valve and mitral valve of the heart within one cycle is called the first wave, and the vibration caused by the closure of the meniscus valve is called the second wave. Generally, the first wave a is large as shown in FIG.
The second wave b is small. However, if only the maximum value is measured, the first wave a and the second wave b may be mistaken.
When the initial value of the interval of the first wave a is obtained from the data of more than 1 second in advance, it is preferable to check the magnitude of the first wave a as well. The best size is the height of the second wave + (height of the first wave-height of the second wave). With this value as a threshold, the next first wave is searched. How to find the first wave is 2
Depending on the type, it may be the first peak that exceeds the threshold value, or the maximum value within a predetermined time that exceeds the threshold value. Of course, when the peak on the negative side, that is, the minimum value is obtained, the minimum value may be found instead of the maximum value. This is because the first peak is not always larger than the second peak, and our experiments have shown that either one produces a breathing curve. There is.

The above-mentioned time interval is the time interval measuring unit 6
Is measured and stored in the time interval storage unit 7, and when the first heartbeat is found, the second heartbeat is searched for in the spare time storage unit 8 from the value stored in the time interval storage unit 7. The maximum value search is performed a little before the stored preliminary time. It is appropriate that the preliminary time is about 25 ms.
When the second heartbeat is found, the interval is stored again in the time interval storage unit 7 and used for the next peak search.

Next, the linear interpolation unit 9 uses the height and time of the peak thus obtained to obtain a curve by linear interpolation, for example. Specifically, the peak of the first heartbeat is time x1, and the size or height y1 is obtained.
Similarly, if x2 and y2 are obtained in the peak of the heartbeat, the following equation is applied and linear interpolation is performed to obtain x1 and x2.
Make data for two. y = (y1-y2) * x / (x1-x2) + y1- (y
1-y2) · x1 / (x1-x2) Of course, linear interpolation is not essential, and any kind of interpolation may be used, but since it is the easiest to implement, here,
It is explained by linear interpolation.

After the above processing is completed, the data relating to the second heartbeat is replaced with the data relating to the first heartbeat, and the data relating to the second heartbeat is obtained again. Repeat this to measure.
The signal thus output represents a breathing curve.
Although not essential, the resulting signal is added to the low-pass filter unit 10 as shown in FIG.
Smoothing with z further approximates the breathing curve. Of course, it doesn't stick to 0.5 Hz. In this way,
FIG. 5 is a graph showing the results calculated one by one according to the embodiment.
Then, a curve similar to the breathing curve of FIG. 4 is obtained.
In that example, the curve was obtained with the negative envelope of the heartbeat waveform,
It is needless to say that the curve is not limited to this, and a curve may be created from data on the positive side or both.

[0017]

According to the first aspect of the present invention, a detector for detecting a sound or movement generated by the heart is attached, and an output signal from the detector corresponding to one or more cycles of the heart is examined, and breathing is performed. Utilizing the fact that the attenuation characteristic of the organ from the heart to the detector changes due to the influence of respiration and the amplitude of the heartbeat signal is modulated with the opposite phase of the respiratory curve, and the maximum value and / or the minimum value of the initial signal emitted by the heart are used. Since information on the envelope of the periodic signal is created by processing such that multiple values are connected and respiratory information is extracted from this envelope information, detect respiratory information using the signal from the detector. You can Moreover, since the measurement can be performed only by mounting the detector on the body, it is possible to measure the breathing cycle without feeling any strangeness due to addition or restraint during normal office work.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a block diagram of a system capable of implementing a respiratory detection method according to an embodiment.

FIG. 2 is a flowchart of a maximum value calculation process executed as initialization in the system.

FIG. 3 is a graph showing a detector signal detected by the system.

FIG. 4 is a graph showing a respiratory curve obtained by a conventional method.

FIG. 5 is a graph showing a respiratory curve obtained using the same system.

[Explanation of symbols]

 1 Detector 2 Heartbeat measuring unit 3 Respiration measuring unit 4 Peak detecting unit 5 Maximum value memory 6 Time interval measuring unit 7 Time interval storing unit 8 Preliminary time storing unit 9 Linear interpolation unit 10 Low pass filter unit

Claims (1)

[Claims] 1. A detector for detecting sounds or movements generated by the heart is attached at one or more points on the body, and
Examining the output signal from the detector corresponding to a period or more, the maximum value of the initial signal emitted by the heart, and, or, to create information on the envelope of the periodic signal by performing a process such as connecting a plurality of minimum values, A respiratory detection method characterized in that respiratory information is extracted from the envelope information.