JP2002017695A - Pulse wave sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pulse wave sensor reduced in necessary memory capacity or calculation quantity and capable of well discriminating between noise and pulsation. SOLUTION: In the pulse wave sensor wherein an ultrasonic wave is transmitted from a transmission part 10 and the reflected wave obtained by a receiver is converted to a pulse wave in a detection part, a pulsation sensing part specifying pulsation from the pulse wave estimates the timing of next pulsation from an already obtained pulsating pulse wave interval (S11) and the peaks not less than a predetermined value of the pulse waves in the zones Z before and behind the pulsation sensing part are detected and the peak of timing nearest to the estimated timing among those peaks is specified as one caused by pulsation (S13-S15).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse wave detecting device, and more particularly, to a pulse wave detecting device which requires a small storage capacity and a small amount of calculation and is capable of discriminating between noise and pulsation.

[0002]

2. Description of the Related Art Detecting a pulse wave due to a blood flow flowing through an artery is widely used in medical practice and health care. This pulse wave detection is performed not only by palpation but also by electronically automatically detecting a pulse rate and the like using a pulse wave detection device. As a device for electronically detecting a pulse wave and obtaining a pulse rate, a piezo-type piezoelectric element is arranged on an artery as a sensor, and a pulse is detected from a pressure change of the epidermis (a displacement of the epidermis due to pressure) due to a pressure change inside the artery. There are those that detect the pulse rate and those that detect the pulse rate using ultrasonic waves.

In such a pulse wave detection device, it is necessary to distinguish between a pulse wave signal and noise. As a technique for discriminating a pulse wave signal from noise, conventionally, as described in JP-A-7-227383,
A technique using frequency analysis is known. In this method, data including noise is accumulated for a predetermined time, and frequency analysis such as FFT is performed to obtain an average pulse within a predetermined time.

[0004]

However, in a pulse wave detection device that discriminates a pulse wave signal from noise by using frequency analysis, a large amount of data needs to be accumulated for frequency analysis, and a large capacity is required. A storage unit is required, the amount of calculation is large and the calculation takes a long time, only the average pulse rate within a predetermined time interval is detected, and changes for each pulse, fluctuations of the pulse, etc. can be obtained. Only regular noise that cannot be obtained is recognized as noise, and noise generated irregularly is not identified as a pulse wave signal. Therefore, further improvement of the pulse wave detection device is required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the prior art pulse wave detecting device.
It is an object of the present invention to provide a pulse wave detection device which requires a small storage capacity and a small amount of calculation, and is capable of satisfactorily discriminating between noise and beat.

[0006]

According to the present invention, there is provided a pulse wave detecting means for detecting a pulse wave, and a pulsation estimating means for predicting a pulsation timing based on the pulse wave detected by the pulse wave detecting means. ,
Range determining means for determining a predetermined width before and after the timing of the pulsation predicted by the pulsation predicting means, and a pulse wave detected by the pulse wave detecting means at the predetermined width determined by the range determining means. A pulse wave detecting device (1st pulse wave extracting device), comprising: a pulse candidate extracting unit for detecting a pulse candidate; and a pulse specifying unit for specifying a pulse from among the candidates extracted by the pulse candidate extracting unit. The above object is achieved by providing (Configuration).

In the pulse wave detecting apparatus according to the present invention, since the pulsation is detected from the pulse wave having a predetermined width before and after the expected pulsation timing, the data for detecting the pulsation can be reduced. A large-capacity storage unit is not required for motion detection, and the amount of calculation is small.

According to the present invention, in the pulse wave detecting apparatus having the first configuration, the pulsation predicting means determines the timing of the next pulsation based on the already acquired pulsation interval or pulse rate. An anticipated pulse wave detection device (second configuration) is provided. According to the present invention, in the pulse wave detection device according to the first configuration or the second configuration, the pulsation identification unit extracts the timing predicted by the pulsation prediction unit and the pulsation candidate extraction unit. A pulse wave detection device (third configuration) for determining a pulse based on the timing of the beat candidate.

According to the present invention, in the pulse wave detecting device of the third configuration, the range determining means sets the predetermined width before and after the predicted pulsation timing to a predetermined width before and after the predicted pulsating timing. A plurality of zones including a first zone and a second zone including the expected pulsation timing and following the first zone are divided and determined, and the pulsation identification unit includes:
A pulse wave detection device (fourth configuration) is provided which immediately identifies a beat candidate first detected in the second zone as a beat.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the pulse wave detecting device according to the present invention will be described below in detail with reference to FIGS. (1) Overview of the present embodiment In the pulse wave detecting device of the present embodiment, an ultrasonic wave f0 having a frequency of 10 MHz is transmitted from the transmitter 11 toward the artery 2 from the body surface (transmitting means), and a reflection target (measurement target) The receiver 21 receives the reflected wave f1 frequency-modulated by the Doppler effect of the blood flow as an object (receiving means). And this received wave is F
A pulse wave is extracted by performing M detection. The pulsation is detected as the peak of this pulse wave. In the present embodiment, the timing of the next pulsation P1 is predicted from the interval from the already detected pulsations P00 and P0 and the timing of the pulsation P0, and is detected within a predetermined range before and after the predicted P1 timing. The obtained peak is specified as a beat P1. As described above, in the present embodiment, based on data that has already been acquired, peaks that are not included in the predetermined range are treated as noise,
The pulsation is determined only from the peaks included in the predetermined range. Therefore, the memory capacity and the amount of calculation are small.

(2) Details of the present embodiment FIG. 1 shows the configuration of the pulse wave detecting device according to the first embodiment. As shown in FIG. 1, the pulse wave detecting device includes a transmitting unit 10, a receiver 21, a detecting unit 30, a pulse wave information acquiring unit 40, and an output unit 50. Also, a control unit (not shown) having a timer and controlling each of the above-mentioned units and a storage unit (not shown) are provided. Transmitter 1
The receiver 0, the receiver 21, and the detection unit 30 function as a pulse wave detecting unit that transmits an ultrasonic wave to an artery and detects a pulse wave from a reflected wave. The pulse wave information acquisition unit 40 receives the detected pulse wave from the detection unit 30 and, based on the pulse wave, a pulsation prediction unit that predicts the timing of pulsation, and a pulsation predicted by the pulsation prediction unit. Range determining means for determining a predetermined width (Zone Z) before and after the timing of (i), pulsation candidate extraction means for detecting a peak as a pulsation candidate from a pulse wave detected in the determined predetermined width (Zone Z) , And functions as a pulse specifying means for specifying a pulse from the extracted candidates.

The transmitting section 10 includes a transmitter 11 disposed on the body surface and a driving circuit 12 for driving the transmitter 11 to transmit an ultrasonic wave. Ultrasound is transmitted to it. The receiver 21 is arranged on a body surface artery near the transmitter 11. The receiver 21 receives the ultrasonic wave transmitted from the transmitter 11 and propagated in the body including the artery, and supplies the received signal to the detector 30.

The detection section 30 includes a high-frequency amplification circuit 31 and
An F / V conversion circuit 32 and a detection circuit 33 are provided.
The high-frequency amplifier circuit 31 is a circuit that amplifies the reflected wave f1 and supplies it to the F / V conversion circuit 32. F / V conversion circuit 32
Is a circuit that outputs a voltage according to a frequency value by using a change in a voltage gain according to a frequency value. Detection circuit 3
Reference numeral 3 denotes a circuit that outputs a voltage (a voltage waveform that changes according to a pulse waveform) corresponding to the envelope by amplitude detection.

The pulse wave information acquiring section 40 includes a pulsation detecting section 41
And a pulse rate calculation unit 42. Beat detector 41
Outputs the voltage waveform supplied from the detection circuit 33 to the output unit 50.
Output, and the pulsation is detected from this voltage waveform,
The detected beat and its timing are output to the pulse rate calculating unit 42. The pulse rate calculator 42 calculates the pulse rate N per minute based on the pulse from the pulse detector 41 and its timing. The pulse rate N calculated by the pulse rate calculation unit 42 is supplied to the output unit 50. The pulse rate calculation unit 42 also supplies a pulse waveform (voltage waveform) to the output unit 50.

The output unit 50 includes a display unit 51, and digitally displays the pulse waveform and the pulse rate N supplied from the pulse rate calculation unit 42. The display unit 51
The pulse rate may be displayed as an image by using a liquid crystal display unit, or the pulse rate may be displayed electronically on a panel.

Next, the operation of the present embodiment configured as described above will be described. FIG. 2 is a flowchart illustrating the flow of the pulse wave detection process according to the present embodiment. When the pulse wave detection process is started in the present embodiment,
As shown in FIG. 2, the control unit turns on the drive signal to the drive circuit 41, starts the transmission of the ultrasonic wave from the transmitter 11, and detects the peak of the pulse wave waveform acquired from the reflected wave as the pulsation detection unit. 41 (step 1). FIG. 3 shows output waveforms at each component of the pulse wave detection device.
When the pulse wave detection processing is started, as shown in FIG. 3A, the transmitter 11 emits an ultrasonic wave f0 having a predetermined frequency toward the artery. This ultrasonic wave f0 is reflected by the blood flowing through the artery 2, and as shown in FIG. 3B, frequency modulation (FM modulation) is performed by the Doppler effect when reflected.
The received reflected wave f1 is received by the receiver 21. After the signal based on the reflected wave f1 from the receiver 21 is amplified by the high frequency amplifier circuit 31, the F / V conversion circuit 32 changes the frequency as shown in FIG. In the detection circuit 33, the change in amplitude is amplitude-detected and converted into a pulse wave waveform that changes in voltage according to the envelope as shown in FIG. This pulse wave waveform is supplied to the pulse detection unit 41. Further, the pulse wave waveform is further supplied to the display unit 51 via the pulse rate calculation unit 42 and is displayed as an image.

Then, the pulsation detecting section 41 converts the pulse waveform shown in FIG.
The peak P is detected, and a peak exceeding a predetermined threshold among the detected peaks P is specified as a peak corresponding to the pulsation. When the peak P corresponding to the beat is specified, the detection timing of the peak P is stored in the storage unit.
Note that the voltage waveform output from the detection circuit 33 may be differentiated, and the peak of the differentiated waveform that exceeds a predetermined threshold may correspond to the pulsation.

The control unit detects the elapsed time after the start of the pulse wave detection processing by using a timer (step 3).
If two peaks equal to or greater than the predetermined value are not detected even after the predetermined time has elapsed (Step 3; Y) (Step 5; N), the control unit, as a warning process, displaces the position of the sensor to the display unit 41. To warn the wearer by displaying an indication that there is a possibility of
1). At the same time as the warning processing, a button for an end command is displayed, or an inquiry as to whether to stop the measurement is displayed, and the end command can be input. If there is an end command (step 23; Y), the pulse wave detection process is immediately terminated. If there is no end command (step 23; N), the timer is returned to 0 and the process returns to step 3. The peak detection process is performed again within a predetermined time from the point of return.

If two peaks equal to or more than a predetermined value are detected within a predetermined time (step 3; Y and step 5; Y), the timing of the two detected peaks is stored in the pulse rate calculation unit 42 from the storage unit. And the pulse rate N is calculated.
The calculated pulse rate N is output to the display unit 51 and displayed. In addition, after the two peaks equal to or more than the predetermined threshold value, the pulse wave waveform is continuously input to the pulsation detection unit 41, and the control unit causes the pulsation detection unit 41 to output the two detected peaks. The timing of the next beat is predicted from the timing of (step 11), and it is determined that the peak detected following the two detected peaks is likely to be due to the beat based on this prediction. Set the zone (step 1
3).

FIG. 4 is an explanatory diagram showing the prediction of the timing of the next beat and the setting of the zone in the beat detector 41. As shown in FIG. 4, in the present embodiment, the newest (last) specified as a pulsation
Time interval R between peak P0 and preceding peak P00
Assuming that R0 is the same as the time interval t from the timing of the most recent peak P0 specified as a beat to the next beat P1, the timing of the next beat P1 is predicted. That is, t (= RR) from the timing of beat P0
After 0), it is predicted as the timing of the next beat. As described above, in the present embodiment, the next beat is predicted using the pulse interval RR of the two beats acquired before the previous beat, and the amount of calculation for predicting the next beat is small. And the required storage capacity can be reduced.

In the zone setting process (step 13), the zone Z is set so as to be Y% of the pulsation interval RR0 (= t) before and after the expected timing of the next pulse. . That is, in the zone Z, the start point is t × (100−Y) / 100 after the peak P0 of the immediately preceding beat, and the end point is t × (100 + Y) / 100 after P0.

FIG. 5 shows that the pulsation P is detected at the time of rest / relaxation, the interval RR from the previous pulsation P, the pulse rate N,
9 is a table showing a result of calculating a rate of change of a beat interval RR. FIG. 6 is a graph of the table of FIG. 5, wherein (a) represents a temporal change in the pulse rate N, (b) represents a temporal change in the beat interval RR,
(C) shows the rate of change of the beat interval RR. As shown in FIGS. 5 and 6, at the time of rest and relaxation, the beat interval RR and the pulse rate N are approximately ± 10% of the beat interval RR and the pulse rate N of the previous beat. In range. That is, with respect to the timing after the same interval as the previous beat interval RR (the expected timing of the next beat), the actual next beat is changed from 10% before to 10% after the beat interval RR. Is detected. Therefore, in the pulse wave detection at the time of rest and relaxation, the zone Z can be almost detected by setting each to 10% of the predetermined time t, and can be almost completely detected by setting it to 20% of t. it can. In addition, if it exceeds 20%, the detection accuracy can be further improved. But,
If the ratio with respect to t is increased, power consumption is increased. Therefore, the ratio is preferably about 20% to 50%. Although not shown in these figures, the pulse wave fluctuation during exercise or tension is smaller than at rest / relaxation, so that the zone Z is set to 20% or less of t, for example, 10% to 15%. Even if it is set to the degree, the pulsation can be detected almost accurately.

The length of the zone Z (the value of Y) is determined based on the interval between the two peaks detected in step 11 to determine whether the subject is at rest / relaxation or at tension / exercise. Alternatively, it may be determined by an input from the operator side. For example, when resting or relaxing, set the length of zone Z to 20 of t.
%, And may be set to 10% of t during tension and exercise. As described above, by increasing or decreasing the zone Z according to the state of the subject, the power consumption can be further reduced.
Pulses can be reliably detected. Further, the length of the zone Z (the value of Y) may be increased during the period close to the start of driving, and may be decreased according to the pulse rate and the pulse interval thereafter. As a result, it is possible to reduce erroneous detection shortly after the start of the measurement and to set the zone Z in accordance with the actual pulse wave state of the subject, thereby suppressing power consumption. After the two peaks equal to or larger than the predetermined threshold, the pulse wave waveform based on the reflected wave f1 is continuously input to the pulsation detecting unit 41. Then, the control unit causes the pulsation detecting unit 41 to detect a peak based on the new pulse wave waveform, and based on the timing of this peak and the zone set by the zone setting process (step 13), a new pulse is detected. A pulsation determination process is performed to determine whether the peak of the wave is due to pulsation (step 15).

In the pulsation specifying process, when only one peak is detected in the zone Z, it is determined that this peak is a pulsation. If there are a plurality of peaks, the peak detected at the timing closest to the predicted pulsation timing among the peaks is determined to be the pulsation. When the peak due to the pulsation is determined, the control unit reads the generation timing of the peak corresponding to the pulsation from the timing recorded corresponding to the pulse wave waveform, and stores the read timing in the storage unit. When a plurality of peaks are detected in the zone Z, the one with the larger peak value can be specified as a beat. When the peak corresponding to the pulsation is specified (Step 17; Y), the pulse rate calculation unit 42 determines the timing of the peak specified as the pulsation and the immediately preceding peak stored in the storage unit. The pulse rate N is calculated from the peak timing of the pulsation. The display section 41 digitally displays the supplied pulse rate N together with the pulse waveform on a liquid crystal display screen. Further, the presence of a pulse is indicated by performing a green blinking display according to the supplied pulse signal. The user can visually recognize his or her pulse wave by seeing this green blinking. Note that a pulse sound may be output according to the supplied pulse signal so that the presence of a pulse can be recognized by hearing.

If no peak exceeding a predetermined value is detected in the zone Z in the pulsation determination process (step 15) (when the pulsation timing is not acquired) (step 17; N), the control unit Performs a timeout process (step 25). As the time-out process, a peak corresponding to a pulsation is detected, for example, by setting the value of the variation ratio Y to be large and setting the zone Z wide or setting a predetermined value for detecting a peak in the zone Z to be large. A process of changing the setting to make it easier, a process of displaying on the display unit 41 that there is a possibility that the position of the sensor may be shifted, a process of generating a beep to call attention to the wearer, and a process of predicting Assuming that a pulse is detected at the given beat timing, the peak timing of the beat is stored in a memory, and the pulse rate N is calculated and displayed.

If there is a peak identified by the pulsation detecting section 41 as a pulsation in step 15 (step 1)
7; Y) and after the timeout process (step 25)
Later), the control unit checks whether there is an end command (step 3).
1) If there is no end command (step 31; N),
Returning to step 11, the timing of the next beat is predicted from the timing of the most recent beat and the two peak timings corresponding to the preceding beat, and the same processing is repeated thereafter. When there is an end command after the warning process (after step 21) (step 23; Y) and after the timeout process (step 2)
5) When an end command is detected (step 31; Y)
Then, the drive circuit 12 is stopped to stop the transmission of the ultrasonic wave from the transmitter 11, or the end processing such as the stop of the peak detection processing by the pulsation detection unit is performed, and the pulse wave detection processing is ended.

As described above, in the present embodiment, peaks not included in the predetermined time range (zone Z) are treated as noise, and the pulsation is determined only from the peaks generated in zone Z. The capacity of the storage unit and the amount of calculation are small. Further, since frequency analysis is not used, noise that does not occur regularly can be recognized as noise. Further, since the peak corresponding to each beat is detected, it is possible to detect the change in the pulse rate and the fluctuation of the beat for each beat.

Next, a second embodiment of the pulse wave detecting device of the present invention will be described. The configuration of the pulse wave detection device according to the second embodiment is the same as the configuration of the first embodiment except that the functions, operations, and output signals of each unit are partially different. Will be described, and the description of the same portions will be omitted as appropriate.

In this embodiment, the zone Z is divided into a plurality of zones, and based on which zone the peak timing of the detected pulse waveform is a peak corresponding to the pulsation. Is determined. Zone Z
Sets a zone I (first zone) prior to the predicted beat timing and a zone II (second zone) following the first zone including the zone predicted beat timing. Contains. In the present embodiment, the zone Z includes only these two zones. With respect to the peak detected in the I-th zone, the determination as to whether or not the peak corresponds to the pulse is reserved, and the peak detected in the II-th zone is reserved. The determined peak is immediately identified as corresponding to the pulsation, the pulsation determination processing is terminated, and timing prediction and zone setting of the next pulsation are started. In this way, different processing is performed depending on which of the zones includes the timing of the detected peak, and when the probability that the peak corresponds to the pulsation is high, the peak signal is immediately pulsated. And the pulsation determination process is terminated. Therefore, with less calculation amount and storage capacity,
The pulsation can be specified.

The main flow of the pulse wave detection processing according to this embodiment is the same as that of the above-described first embodiment shown in FIG.
First we get the timing of the two peaks, and from these,
Predict the timing of the next beat (Steps 1 to 2 in FIG. 2)
Step 11). After predicting the timing of the next beat, a zone setting process is performed. FIG. 7 is an explanatory diagram illustrating the prediction of the timing of the next beat and the setting of the zone in the present embodiment. In the zone setting process according to the present embodiment, as shown in FIG. 7, a zone Z similar to the above-described first embodiment, and an I-th zone and a II-th zone are determined. The I-th zone is set in the zone Z, in which the time is closer to the timing of the predicted beat P1. The zone II is set so as to cover a range other than the zone I in the zone Z, includes the predicted timing of the beat P1, and is set to a time after the zone I.

The range of the zone Z is the same as that of the first embodiment, and is set so as to be Y% before and after the expected timing of the next beat. The starting point of the zone Z is set to the peak of the immediately preceding beat. From P0, after t × (100−Y) / 100,
The end point is t × (100 + Y) / 100 after P0. The start of the zone I is the same as that of the zone Z, and the end of the zone I and the start of the zone II are both t × (100
−M) / 100, where Y>M> 0. I
The end point of the I zone is the same time as the end point of the zone Z.
The start point of zone Z and zone I, the end point of zone I and the start point of zone II, and the end point of zone Z and zone II are the pulsation interval RR from peak PO, respectively.
It is possible to determine in advance the ratios (referred to as A%, B%, and C%) that are equal to 0, and obtain the ratios.
A = 100−Y, B = 100−M, C = 100 + Y
It is.

Then, a beat detection process is performed after the zone setting process. In the pulsation detection process according to the present embodiment, it is assumed that the peak of the pulse wave waveform that occurs at a timing outside the range of the zone Z is caused by noise, not pulsation. Regarding a peak generated at a timing within the range of the zone Z, it is determined that the detected timing is the I-th zone or the II-th zone, assuming that the peak close to the expected timing is due to the pulsation. Perform processing based on

FIG. 8 is a flowchart showing the flow of the pulsation determination process by the pulsation detecting section 41 of the present embodiment.
When the zone setting process ends and the beat determination process starts,
As shown in FIG. 8, the pulsation detecting unit 41 monitors whether a peak of the pulse waveform is detected (step 151). Then, when a peak is detected (Step 151; Y), it is checked whether or not the timing of the acquired peak is in the I-th zone (Step 153). The zone I is set before the timing of the next expected beat, and a peak closer to the expected timing may be detected later. Then, the data of the detection timing is stored in the memory (step 155). At this time, if the peak data is already stored in the memory, the stored data is discarded because the peak detected later in the I-th zone is closer to the expected timing. Then, the new peak signal data is overwritten and stored. Therefore,
In the area where the data of the detected peak signal is stored, the data of the latest detected peak in the I-th zone is always stored. Then, the process returns to step 151, and the presence or absence of a peak is monitored again.

A peak is detected (step 151;
Y) If the timing of the peak falls within the zone II (step 153; N), it is checked whether or not the storage unit has data of the reserved and stored peak timing (reserved data). (Step 157) If there is no pending data, since the peak is more likely to be closer to the predicted timing than the peak detected later, the pulsation is specified by regarding this peak as the pulsation (step 157). Step 159). When the reserved data is stored, the reserved data is detected in the I-th zone. Then, for each of the detected data and the hold data, a difference between the predicted beat timing and the peak is compared, and a peak close to the predicted beat timing is specified as a beat (step 161).

If no peak is detected at step 151 (step 151; N), it is checked whether or not the current time is within the zone (step 163).
3; Y), it is checked whether or not the storage data is stored in the storage unit (step 165). When data is stored in the storage unit, the reserved data is the data of the peak detected most recently in the I-th zone.
Then, the peak of the reserved data is identified as corresponding to the beat. If the peak has not been detected and the timeout has not occurred, the process returns to step 151 to continue monitoring whether or not a peak has been detected. After the peak corresponding to the beat is determined (after step 159, step 161)
After that, and when the timeout occurs without detecting the peak (step 165; N), the pulsation determination processing is ended.

After the pulsation determination process, the processes after step 17 in FIG. 2 are performed as in the first embodiment. That is, a time-out process is performed as necessary depending on whether or not a peak corresponding to a beat is determined in the beat determination process (FIG. 8), and the timing of the next beat is predicted until there is a termination command by an operator's input or the like. (Step 11 in FIG. 2) and subsequent steps are repeated. If there is a termination instruction, the pulse wave detection processing is terminated.

As described above, in the present embodiment, the zone Z in the predetermined range before and after the predicted beat is defined as including the I-th zone whose time is before the predicted beat timing and the predicted beat. The peak of the pulse wave waveform detected in the I-th zone is set to be divided into the II-th zone following the I-th zone, and since only the latest data is stored in the storage unit, the storage capacity is small. I'm done. In addition, the pulse waveform is
When the peak is detected for the first time in zone II without being detected in the zone, the peak is immediately identified as being due to the pulsation, so that the storage capacity and the amount of calculation are small. If the peak of the pulse waveform is detected in Zone II while the peak of the pulse waveform is detected in Zone I and the data is stored in the storage unit, the data is immediately stored in the storage unit. Since the peak corresponding to the pulsation is determined by comparing only the peak that is present and the peak detected in the zone II (the first peak in the zone II), the storage capacity and the amount of calculation are small and the time is short. Determines the peak corresponding to the beat. In this case, the comparison between the two peaks is performed by a simple calculation of comparing the time interval with the expected pulsation timing. Is determined. As described above, in the present embodiment, the pulsation may be determined before the entire range of the zone Z has elapsed. can do.

Also, since frequency analysis is not used,
Noise that does not occur regularly can be recognized as noise. Further, since the peak corresponding to each beat is detected, it is possible to detect the change in the pulse rate and the fluctuation of the beat for each beat.

Next, a third embodiment of the present invention will be described. The configuration of the pulse wave detection device according to the third embodiment is the same as that of the above-described first embodiment except that the functions, operations, and output signals of each unit are partially different.
Only different parts such as functions will be described, and description of the same parts will be omitted.

Also in this embodiment, the zone Z is set by being divided into a plurality of zones, and based on which zone the peak timing of the detected pulse waveform is in,
It is determined whether the peak corresponds to the beat. Zone Z
Sets a zone I (first zone) prior to the predicted beat timing and a zone II (second zone) following the first zone including the zone predicted beat timing. Contains. In the present embodiment, the zone Z includes an I-th zone and a II-th zone, and an I-th zone following the II-th zone.
It consists of three zones, zone II. The determination of whether or not the peak detected in zone I corresponds to the pulse is reserved, and the peak detected in zone II is immediately identified as corresponding to the pulsation and the pulse is determined. The motion determination processing ends, and timing prediction and zone setting of the next beat are started. In this way, different processing is performed depending on which of the zones includes the timing of the detected peak, and when the probability that the peak corresponds to the pulsation is high, the peak signal is immediately pulsated. And the pulsation determination process is terminated. Therefore, it is possible to specify a pulsation with a smaller amount of calculation and a smaller storage capacity.

The main flow of the pulse wave detection processing according to the present embodiment is the same as that of the first embodiment shown in FIG.
First we get the timing of the two peaks, and from these,
Predict the timing of the next beat (Steps 1 to 2 in FIG. 2)
Step 11). After predicting the timing of the next beat, a zone setting process is performed. FIG. 9 is an explanatory diagram showing the prediction of the timing of the next beat and the setting of the zone in the beat detecting unit 41. In the present embodiment, in the zone setting process, as shown in FIG. 9, the same zone Z as in the above-described embodiment is determined.
A zone II and a zone III are determined. I
The zone is set in a zone of zone Z in which the time is closer to the predicted timing of beat P1. I
The I zone is a zone that is the time after the I zone in the zone Z and includes the timing of the predicted beat P1.
The third zone is set so as to cover the range from the second zone onward. In the present embodiment, the zone II is set at D% (Y>D> 0) of the beat interval RR0 before and after the predicted beat P1 timing. Further, the elapsed time of the zone I and the elapsed time of the zone III are set to be equal.

The range of the zone Z is the same as that of the first embodiment, and is set so as to be Y% before and after the expected timing of the next beat, and the starting point of the zone Z is set to the peak of the immediately preceding beat. From P0, after t × (100−Y) / 100,
The end point is t × (100 + Y) / 100 after P0. The I-th zone starts at the same time as the start point of the zone Z, and the end point of the I-th zone and the start point of the II-th zone are both txt (100−
D) / 100, where Y>M> 0. I
The end point of zone I and the start point of zone III are set as t × (100 + D) / 100 from the peak P0 of the immediately preceding beat. The end point of zone III is the same time as the end point of zone Z. In addition, the starting point of zone Z and zone I, the ending point of zone I, the starting point of zone II,
The end point of zone I and the start point of zone III, the end point of zone Z and the end point of zone III are the ratios (A%, D, respectively) corresponding to the beat interval RR0 from the peak PO.
%, E%, and C%) can be determined in advance and determined. A = 100−Y, D = 1
00-D, E = 100 + D, C = 100 + Y.

After the zone setting process, a beat detection process is performed. In the pulsation detection process according to the present embodiment, it is assumed that the peak of the pulse wave waveform that occurs at a timing outside the range of the zone Z is caused by noise, not pulsation. Regarding a peak generated at a timing within the range of the zone Z, it is assumed that the peak closest to the expected timing is due to the pulsation, and the detected timing is determined by any one of the zone I to the zone III. Is performed based on whether

FIG. 10 is a flowchart showing the flow of the pulsation determination process of the present embodiment. As shown in FIG. 10, in the pulsation determination process, the pulsation detection unit 41 detects a peak from the pulse waveform (step 251). Then, when a peak is detected (Step 251: Y), it is checked whether or not the timing of the acquired peak is the I-th zone (Step 253). When the vehicle is in zone I (step 253; Y), the determination of whether or not the peak corresponds to the pulsation is suspended because a peak closer to the predicted timing may be detected later. Then, the data of the detection timing is stored in a memory (step 255). If there is already reserved data at this time, the existing data is of the peak detected earlier in zone I. Among the peak signals detected in the I-th zone, since the later detected signal is close to the predicted timing, the stored data is discarded, and the data of the new peak signal is overwritten and stored. Then, the process returns to step 251.

When a peak is detected (step 251; Y), the peak is in zone II (step 25).
3; N and 261; Y), zone II is the other zone I.
Because it is closer to the expected beat timing than the zone or the zone III, regardless of the presence or absence of the data held in the storage unit, and without losing the peak detection result in the zone III, this II The peak detected in the zone is determined as corresponding to the beat (step 263),
The pulsation determination processing ends.

When a pulse waveform peak is detected in the third zone (step 251; Y and 25)
3; N and 261; N), if the peak of the pulse waveform has been detected in zone II, the pulsation determination must have been completed, so that the peak of the pulse waveform has not been detected in zone II. Become. Then, the beat detecting unit 41 checks whether or not the storage data is stored in the storage unit (step 265). If there is no pending data (step 26
5; N), a peak was detected for the first time in zone III. Since the zone III is in a range after the predicted beat timing, the peak detected in the zone III is closer to the predicted beat timing than the peak detected later. Therefore, the pulsation detection unit 41 determines this peak as corresponding to the pulsation (step 269), and ends the pulsation determination process. If a peak signal is detected in the zone III and there is data already stored in the storage unit (step 265; Y), the stored data is the last of the peaks in the zone I, that is, the peak is predicted. The timing is close to the beat. Then, for each of the peak timing of the zone I and the peak timing of the newly detected zone III, the difference between the predicted pulsation timing is compared. Then, the peak closer to the predicted pulsation timing is determined to correspond to the pulsation (step 267), and the pulsation determination processing ends. As a result, the peak closest to the predicted beat timing among the peaks detected in zone I,
Among the peaks detected in the I zone, the one closer to the predicted pulsation timing is specified as the pulsation peak.

If it is determined in step 251 that a peak has not been detected (step 251; N) and the time has elapsed after passing zone Z (step 257; Y), it is checked whether or not there is any pending data. The data reserved at this time is the data of the peak detected in the zone I and the latest peak. If there is pending data (step 258; Y), this peak is determined to correspond to the pulsation, and this data is stored in a predetermined area of the storage unit (step 259), and the pulsation determination processing ends. I do. No peak is detected (step 251;
N) Time-out (step 257; Y), when there is no pending data (step 258; N), it means that the time-out has occurred without the peak being detected since the start of the beat determination process. At this time, the ending process is performed without specifying the pulsation, and the pulsation determining process ends.

After the pulsation determination processing, the processing after step 17 in FIG. 2 is performed as in the first embodiment. That is, depending on whether or not the peak corresponding to the pulsation is determined in the pulsation determination process (FIG. 10), a time-out process is performed as necessary, and the timing of the next pulsation is issued until there is an end command by an input from the operator or the like. The processing after the prediction (step 11 in FIG. 2) is repeated. If there is a termination instruction, the pulse wave detection processing is terminated.

As described above, in the present embodiment, the zone Z in the predetermined range before and after the predicted beat is defined as the zone I including the predicted beat in the I-th zone whose time is before the predicted beat timing. The zone is divided into a zone II following the zone I and a zone III following the zone II, and the peak of the pulse wave waveform detected in the zone I stores only the data of the latest one in the storage unit. Therefore, the storage capacity is small. In addition, when the pulse wave waveform is not detected in the zone I and is detected in the zone II for the first time, the peak is immediately identified as being caused by the pulsation, so that the storage capacity and the amount of calculation are small. If the peak of the pulse waveform is detected in zone III while the peak of the pulse waveform is detected in zone I and the data is stored in the storage unit, the data is immediately stored in the storage unit. The peak corresponding to the pulsation is determined by comparing only the peak that is present and the peak detected in zone III (the first peak in zone III), so that the storage capacity and the amount of calculation are small and the time is short. Determines the peak corresponding to the beat. In this case, the comparison between the two peaks is performed by a simple calculation of comparing the time interval with the expected pulsation timing. Is determined. As described above, in the present embodiment, the pulsation may be determined before the entire range of the zone Z has passed, and the peak corresponding to the pulsation can be detected in a short time by reducing the amount of calculation and the necessary storage capacity. can do.

Also, since frequency analysis is not used,
Noise that does not occur regularly can be recognized as noise. Further, since the peak corresponding to each beat is detected, it is possible to detect the change in the pulse rate and the fluctuation of the beat for each beat.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to such embodiments, and other embodiments can be adopted and modified within the scope of the present invention. It is. For example, in each of the above-described embodiments, immediately after the start of the pulse wave detection process, two peaks equal to or more than a predetermined threshold are detected from the pulse wave, and these are used as peaks due to the pulse to predict the next pulse. (Step 5
Step 11), obtaining a predetermined number of peaks that are equal to or more than a predetermined value from the pulse wave, obtaining an average peak interval from the time and the number of peaks during the interval, and predicting the next beat from the peak interval. It may be. Immediately after the start, assuming a resting time, the beat interval is set to a predetermined interval of 1000 msec (6
(0 beats / sec) or 857 msec (70 beats / sec), the next beat may be predicted. Further, a plurality of values such as an interval at rest and an interval at tension / exercise may be stored, and the next pulsation may be predicted from the interval selected by the operator.

Further, a change in the interval between a plurality of continuous beats within a predetermined time interval and a change in the pulse rate of the continuous pulse are obtained, and a predetermined time t is determined from any of these changes, and the next time t is determined. The pulsation may be predicted. For example, as shown in FIG. 11, when the pulse rate is reduced by approximately 7% in the continuous pulse interval, the next pulse interval is also in a range RR (min) before and after a value that is further reduced by 7% from the previous pulse interval. ) To RR (max), and the next beat interval RR0 (= predetermined time t) is predicted based on this beat interval. In this way, by predicting the next pulse taking into account the change in the pulse interval and the pulse rate, even when the pulse interval is changed due to the start and end of exercise, tension, etc., with high accuracy. The next pulse is predicted, and an appropriate peak can be specified as a pulse due to the pulse wave waveform.

In each of the above-described embodiments, the timing of the next beat is predicted from the peak timing (beat timing) corresponding to the already obtained beat except immediately after the start of the pulse wave detection process. Although the beat timing already obtained is used to identify the peak due to the next beat, in addition to this, for example, ultrasonic waves are emitted only at predetermined intervals before and after the expected beat. It may be used in common for other purposes such as transmission. In each of the above-described embodiments, the pulse wave is detected by utilizing the fact that the frequency of the reflected wave fluctuates due to the pulse wave by transmitting the ultrasonic wave, but the pulse wave detection method is not limited to this. Not a thing,
For example, a pulse wave may be detected by using the fact that an ultrasonic wave is transmitted and the amplitude of the reflected wave fluctuates due to the pulse wave. Alternatively, a piezo-type piezoelectric element may be used as a sensor to detect a pulse wave from a change in epidermal pressure (a displacement of the epidermis due to pressure) accompanying a change in pressure inside the artery.

The pulse wave detecting device of the present invention can be incorporated into a watch to transmit ultrasonic waves to the radial artery and the ulnar artery using a transmitter having a transmission frequency of 32 KHz used in the watch. In each of the above embodiments,
Ultrasound is continuously output during pulse wave detection, and a continuous pulse wave waveform is detected. However, two or more peaks of the pulse wave waveform are detected, and the timing of the next pulse is predicted. Thereafter, an ultrasonic wave may be transmitted only for a time within the zone Z, or a pulse waveform or peak may be obtained only for a time within the zone Z.

[0055]

According to the pulse wave detecting apparatus of the present invention, the next pulse is predicted, and the next pulse is detected from the pulse wave information within a predetermined time before and after the predicted pulse including the next pulse. In addition, the storage capacity and the amount of calculation of the pulse wave information for detecting the next pulsation can be reduced, and the pulsation can be detected in a short time to obtain information about each pulsation.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a pulse wave detection device according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing a processing flow of a pulse wave detection process by the pulse wave detection device of FIG.

FIG. 3 is an explanatory diagram showing an output waveform in each component of the pulse wave detection device of FIG. 1;

FIG. 4 is an explanatory diagram showing prediction of a timing of a next beat set by a beat detecting unit and setting of a zone in the pulse wave detecting device of FIG. 1;

FIG. 5 shows a pulse signal P detected at the time of rest / relaxation, a pulse rate N, an interval RR between the pulse signal P and the pulse rate N,
9 is a table showing the results of calculating the rate of change of the pulsation interval RR.

FIG. 6 is a graph of the table of FIG. 5;
Represents the temporal change of the pulsation interval RR, (b) represents the temporal change of the pulse rate N, and (c) represents the pulsation interval RR
It shows the rate of change.

FIG. 7 is an explanatory diagram showing prediction of a timing of a next beat set by a beat detecting unit and setting of a zone in the pulse wave detecting device according to the second embodiment of the present invention.

FIG. 8 is a flowchart showing the flow of a beat determination process according to the embodiment of FIG. 7;

FIG. 9 is an explanatory diagram showing prediction of the timing of the next beat set by a beat detector and setting of a zone in the pulse wave detector according to the third embodiment of the present invention.

FIG. 10 is a flowchart showing a flow of a beat determination process according to the embodiment of FIG. 9;

FIG. 11 is an explanatory diagram showing a method of determining a predetermined time t in another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Transmitting part 11 Transmitter 12 Drive circuit 21 Receiver 30 Detection part 31 High frequency amplification circuit 32 F / V conversion circuit 33 Detection circuit 40 Pulse wave information acquisition part 41 Pulse detection part 42 Pulse rate calculation part 50 Output part 51 Display part

Claims (4)

[Claims] 1. A pulse wave detecting means for detecting a pulse wave, a pulse estimating means for estimating a pulsation timing based on a pulse wave detected by the pulse wave detecting means, Range determining means for determining a predetermined width before and after the timing of the beat to be performed; and detecting a pulse candidate from the pulse wave detected by the pulse wave detecting means at the predetermined width determined by the range determining means. A pulse wave detecting apparatus, comprising: a pulsation candidate extracting unit that performs a pulsating process; and a pulsation specifying unit that specifies a pulse from the candidates extracted by the pulsating candidate extracting unit. 2. The pulse wave detection device according to claim 1, wherein the pulse predicting unit predicts the timing of the next pulse based on a pulse interval or a pulse rate that has been acquired. apparatus. 3. The pulsation identification unit, based on the timing predicted by the pulsation prediction unit and the timing of the pulsation candidate extracted by the pulsation candidate extraction unit,
The pulse wave detecting device according to claim 1 or 2, wherein the pulse is determined. 4. The range determining means sets a predetermined width before and after the expected beat timing to a first zone before the expected beat timing and the expected beat timing. And a plurality of zones including a second zone following the first zone are determined. The pulsation identification unit immediately pulsates a pulsation candidate detected first in the second zone. The pulse wave detection device according to claim 3, wherein the pulse wave is specified as: