JPH0347088B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a pulse wave signal processing device for removing noise from a pulse wave signal representing a pulse wave generated from an artery of a living body in synchronization with a heartbeat. .

BACKGROUND ART Devices are known that detect pulse waves generated from the arteries of a living body in synchronization with heartbeats and determine the state of the living body based on the pulse waves. For example, a blood pressure measuring device. This blood pressure measuring device generally measures a blood pressure value based on a pulse wave that changes in relation to a change in pressure of a cuff attached to compress a part of the human body. Generally, the methods are classified into microphone methods, oscillometric methods, ultrasonic methods, etc., depending on the target pulse wave. In other words, in the case of a microphone-type blood pressure measuring device, the Korotkoff sound generated in the arteries in synchronization with the heartbeat (hereinafter simply referred to as heartbeat) is used as a pulse wave, and the blood pressure value is measured based on this Korotkoff sound. In the case of an oscillometric blood pressure measuring device, the pressure vibrations generated within the cuff in synchronization with the heartbeat are detected as pulse waves, and the blood pressure value is measured based on this. In the case of a sound wave type blood pressure measuring device, the pulsation of the surface wall of the artery that occurs in synchronization with the heartbeat is used as a pulse wave, and the pulsation of the surface wall of the artery is detected by ultrasound, and the blood pressure is measured based on the detection signal. It is designed to measure the value.

By the way, in this type of blood pressure measuring device,
Because the frequency components are similar to pulse waves and are difficult to remove by ordinary means such as filters,
It is unavoidable that noise such as motion artifacts caused by the electric scalpel or the subject's body movements is mixed into the pulse wave, and this noise mixed into the pulse wave makes it difficult to measure blood pressure values. There was a problem that the accuracy decreased. Therefore, one of the challenges in this type of blood pressure measuring device is to prevent the measurement accuracy from decreasing due to the noise introduced above, and various methods have been proposed to solve this problem. There is.

For example, in a microphone-type blood pressure measuring device, when a predetermined number of signals or more appear within a certain period of time, a series of signals is recognized as each Korotkoff sound, or an oscillometric blood pressure measuring device is used. In a measuring device, the magnitude of each signal obtained as a pulse wave is compared with the magnitude of the signals before and after it, and any signal that deviates significantly from the magnitude relationship between the magnitudes of the signals before and after it is removed as noise. In an oscillometric blood pressure measuring device, a simple pattern recognition is performed on the signal detected as a pulse wave, and if the recognized pattern is significantly different from the standard pattern, it is removed as noise. .

However, the reality is that the conventional noise removal methods described above do not always effectively prevent noise, and therefore cannot necessarily sufficiently prevent a decrease in the measurement accuracy of blood pressure values. In other words, the method for recognizing Korotkoff sounds in the microphone-based blood pressure measuring device described above is effective against sporadic noise, but is completely ineffective against continuous noise to some extent. For each noise removal method in an oscillometric blood pressure measuring device, when noise of the same magnitude as the pulse wave signal or noise with a similar pattern is introduced, This noise could not be removed, and in particular, there were many cases in which noise of such size and shape that could not be removed was mixed into the pulse wave signal. In addition, in the noise removal method using pattern recognition in an oscillometric blood pressure measuring device, it is thought that noise can be removed effectively if the pattern recognition of each signal is performed strictly, but such strict pattern recognition is not possible. In order to do this, the circuit configuration has to be complicated and the execution time is also long, making it impractical for use as a blood pressure measuring device.

The present invention has been made against the background of the above circumstances, and its purpose is to provide a pulse wave signal processing device that can remove noise mixed in pulse waves more effectively than before. There is a particular thing.

Means for Solving the Problems The gist of the present invention for achieving the above object is to provide a method for removing noise contained in a pulse wave signal representing a pulse wave generated from an artery of a living body in synchronization with a heartbeat. A pulse wave signal processing device comprising: (a) a pulse wave sensor that detects the pulse wave and outputs a pulse wave signal; and (b)
(c) storage means for sequentially storing the pulse wave signals detected by the pulse wave sensor; A primary pulse wave signal sequence in which a series of primary pulse wave signal sequences are created, and the period of the fundamental frequency of the primary pulse wave signal sequence is determined by performing Fourier transform processing or autocorrelation processing on the primary pulse wave signal sequence. (d) selecting a signal having a period within a predetermined range centered on the period of the fundamental frequency from among the signals constituting the primary pulse wave signal sequence; secondary pulse wave signal train creation means for creating a set of secondary pulse wave signal train;
(e) determining the strength of autocorrelation in the period of the fundamental frequency of the plurality of sets of secondary pulse wave signal sequences, respectively;
(f) a secondary pulse wave signal sequence determining means for determining a set having the strongest autocorrelation among the plurality of sets of secondary pulse wave signal sequences; and pulse wave selection means for selecting pulse wave signals corresponding to the set of secondary pulse wave signal sequences determined by the pulse wave signal sequence determination means.

Operation and Effects of the Invention The present invention having the above configuration will be explained with reference to FIG. This noise is uniformly detected as a pulse wave signal, and this is sequentially stored in the storage means. Then, the primary pulse wave signal sequence basic period determining means creates a series of pulse wave signal sequences having a period corresponding to the peak value interval of the pulse wave signal stored in the storage means, and creates the primary pulse wave signal sequence. is subjected to Fourier transform processing or autocorrelation processing to determine the period of the fundamental frequency of the primary pulse wave signal sequence. In other words, the primary pulse wave signal sequence consists of signals based on a large number of regular periodic pulse waves and signals based on a relatively small number of completely randomly generated noises. By finding the fundamental period of the sequence, the fundamental period of the regular pulse wave can be found.

Then, based on the fundamental period of the fundamental frequency of this normal pulse pulse, the secondary pulse wave signal train generating means generates a predetermined signal centered on the fundamental frequency from among the signals constituting the first pulse wave signal train. A plurality of sets of secondary pulse wave signal sequences are created by selecting signals having periods within the specified range. As a result, a number of signal sequences that are considered to be regular pulse waves are created, and non-periodic signals among the signals that constitute the primary pulse wave signal sequence are removed at this stage.

For the multiple sets of secondary pulse wave signal sequences created in this way, the strength of autocorrelation in the period of the fundamental frequency is determined, and the set with the strongest autocorrelation among the multiple sets of secondary pulse wave signal sequences is determined. is determined. The pulse wave selection means selects a pulse wave signal corresponding to the set of secondary pulse wave signal sequences determined by the secondary pulse wave signal sequence determination means from among the pulse wave signals stored in the storage means. be done. This pulse wave signal has irregular noise removed, so
Based on this pulse wave signal, the condition of the living body can be determined with high accuracy. For example, if a blood pressure value is determined based on the pulse wave signal, an accurate blood pressure value can be obtained.

As described above, according to the present invention, extremely accurate blood pressure values can be stably determined regardless of the presence or absence of noise. Furthermore, since the secondary pulse wave signal sequence is created based on the fundamental period determined for the fundamental frequency of the primary pulse wave signal sequence, an extremely large number of sets of secondary pulse wave signal sequences are created based on completely random periods. Compared to the case where the secondary pulse wave signal sequence is used, there are fewer sets of secondary signal sequences, the necessary secondary pulse wave signal sequence can be obtained extremely quickly, and the capacity of the storage means for storing the secondary pulse wave signal sequence is also extremely small. You can get away with it.

Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

FIG. 2 is a block diagram showing an embodiment in which the present invention is applied to an oscillometric blood pressure measuring device. In the same figure, reference numeral 2 denotes a bag-shaped cuff attached to a part of the human body to compress that part, and a pressure signal SP is sent to the cuff 2 to detect the pressure inside the cuff 2 and express the pressure. A pressure sensor 4 that outputs is attached. This pressure signal SP is then supplied to the pulsation detector 6 and the A/D converter 8.

The pulsation detector 6 is composed of a bandpass filter and an A/D converter, and detects noise induced in the cuff 2 by pulse waves (vibration components) included in the pressure signal SP and motion artifacts. A pulse wave signal SM representing the magnitude of the pulse waves and noise and synchronized with the pulse waves and noise is supplied to the I/O port 10. That is, in this embodiment, a pressure sensor 4 that detects the pressure inside the cuff 2 and a pressure signal SP from the pressure sensor 4 are used.
A pulse wave sensor is constituted by the pulse wave detector 6 that detects the pulse wave as a vibration component contained therein and the noise.

On the other hand, the A/D converter 8 is configured with a low-pass filter, and generates a static pressure value signal PV from which pulse waves and noise are removed from the pressure signal SP.
is taken out and supplied to the I/O port 10.

Further, a start push button 12 for instructing the start of measurement is connected to the I/O port 10.
When this is pressed, a start signal SS is supplied to the I/O port 10.

I/O port 10 is connected via the data bus line.
CPU14 (arithmetic processing unit), RAM16 and ROM
18, and supplies a pressure value signal PV, a pulse wave signal (primary pulse wave signal train) SM, and a start signal SS to the data bus line according to instructions from the CPU 14. The CPU 14 executes signal processing using the temporary storage function of the RAM 16 according to the program stored in the ROM 18 in advance, and sends a pump drive signal SA and a discharge amount signal via the I/O port 10.
SE as pump drive device 20 and flow rate adjustment device 22
Similarly, via the I/O port 10, a predetermined blood pressure value determined by signal processing is supplied as a display signal DD to the display 24 for display.

That is, as is clear from the above description, in this embodiment, the pressure value signal PV and the pulse wave signal sequence
The SM is stored in the RAM 16 which has a temporary storage function, and thus this RAM 16 serves as a so-called storage means.

The pump drive device 20 is configured to drive an electric pump connected to the cuff 2 to forcefully feed air into the cuff 2 while receiving the pump drive signal SA, and also controls the flow rate adjustment device 22. is equipped with two exhaust valves, one for rapid exhaust and one for constant speed exhaust,
By controlling the opening and closing of these two exhaust valves according to the contents of the discharge amount signal SE, the amount of discharge from the inside of the cuff 2 can be adjusted.

The operation of this embodiment will be explained below.

When a power switch (not shown) is turned on, power is supplied to each part of the device, and the CPU 14 is preset to ROM1.
The control operation is performed according to the flowchart of FIG. 3 showing the main program stored in 8.

First, step S1 is executed, and the operating state of the start push button 12 is determined. Start push button 12
The execution of step S1 is repeated while the button is not operated, but the start button 12 is pressed to start blood pressure measurement.
When is pressed and the start signal SS is supplied via the I/O port 10, the next step S2
and S3 are executed.

In step S2, the content of the discharge amount signal SE to the flow rate adjustment device 22 is changed, the two exhaust valves that had been in the open state up until then are both closed, and the pump drive signal SA to the pump drive device 20 is changed. The supply of air to the cuff 2 is started, and the pumping of air to the cuff 2 is started. On the other hand, in step S3, it is determined whether the actual pressure P within the cuff 2 represented by the pressure value signal PV is greater than a preset target upper limit pressure PM. While the actual pressure P is still smaller than the target upper limit pressure PM, proceed to step S3.
However, if the actual pressure P exceeds the target upper limit pressure PM, steps S4 and S5 are immediately executed. That is, in step S4, the output of the pump drive signal SA is canceled, the pump drive device 20 stops pumping air into the cuff 2, and the output of the output amount signal SA is canceled.
The contents of SE are changed, the constant speed exhaust valve is opened, and the pressure P inside the cuff 2 is gradually decreased at a constant speed.In step S5, the pulse wave generated during the depressurization process of the cuff 2 is The pulse wave signal SM detected by the sensor and its various information, such as the peak value of each pulse wave signal SM, the interval between each peak value, and the time when the peak value of each pulse wave signal SM was obtained in relation to it. Information such as the pressure P inside the cuff 2 is stored.

Step S6 is executed following step S5, and in order to judge whether all the information necessary to calculate a predetermined blood pressure value has been collected, the actual pressure P in the cuff 2 is determined to be sufficiently small as determined in advance. A comparison is made to see if the pressure has become smaller than the target minimum pressure PO.
Then, unless sufficient information is available to determine whether the actual pressure P is greater than the target minimum pressure PO, proceed to step S.
Steps 5 and S6 are repeated, but when the pressure P becomes smaller than the target minimum pressure PO and it is determined that necessary and sufficient information has been obtained, step S7 is immediately executed and the content of the discharge amount signal SE is changed. The rapid exhaust valve is opened and the gas in the cuff 2 is rapidly exhausted.

Then, step S7 is followed by step S7.
8 and S9 are executed. That is, step S
In Step 8, a primary pulse wave signal train consisting of a series of pulse trains having a predetermined pulse width synchronized with the peak value of the pulse wave signal SM stored in step S5 is created, and an autolog of the primary pulse wave signal train is created. A correlation is taken. And step S9
In step S8, based on the periodicity of the autocorrelation number, the period of the fundamental frequency ₀ , which is the largest frequency component of the pulse train, is determined (fundamental period).
T ₀ is required.

Note that the autocorrelation function here represents the strength of the correlation between two points separated by τ, and is usually expressed as ψ(τ) = () (+) when it is a function s(t). When the function s(t) has hidden periodicity, the periodicity also appears in its autocorrelation function ψ(τ). In addition, the pulse train as the function s(t) for which such autocorrelation is taken in this embodiment includes irregularly occurring noise, but is basically composed of regular periodic pulse wave components. . Therefore, the fundamental period T ₀ found in steps S8 and S9 described above is almost equal to the fundamental period of the signal train consisting only of normal pulse wave components.

After step S9 is executed, step S10 is subsequently executed. That is, this step S10
In step _S9 , the secondary pulse wave signal sequence _s
(t) is created.

The primary pulse wave signal train detected by the pulse wave sensor includes a normal pulse wave component and a noise component caused by motion artifacts and the like. The noise component is included completely irregularly without any relation to the regular pulse wave component, and on the other hand, the interval of the pulse wave component varies somewhat due to the influence of breathing and the like. Therefore, among the signal components that appear in the first pulse wave signal train, the signal that appears every basic period T ₀ is not necessarily a regular pulse wave component, and the signal component does not necessarily appear every basic period T ₀ . do not have. That is, based on this reason, the secondary pulse wave signal sequence
si(t) is a predetermined range ( ₁ ±
0.25) By selecting signals having a period within T ₀ , multiple sets of secondary pulse wave signal sequences are created. Since it is unclear which time point in the primary pulse wave signal sequence, which is a time-series function, is the true peak time point (reference time point) of the pulse wave, the reference time point is successively shifted and determined within the above-mentioned base range. By selecting pulses, several sets of secondary pulse wave signal trains are created. Since one of the plurality of sets of secondary pulse wave signal sequences is a signal sequence synchronized with the regular pulse wave generation cycle, it is determined in the following steps.

Then, step S11 follows step S10.
Then, the secondary pulse wave signal train created in step S10
The autocorrelation ψi(t) for si(t) is determined,
The autocorrelation strength ψi (T ₀ ) at the fundamental period T ₀ is determined. That is, in step S11, the secondary pulse wave signal sequence created in step S10 is
An index of how many pulses synchronized with normal pulse wave components si(t) consists of is determined as a numerical value. The strength of autocorrelation ψi (T ₀ ) as this index is then compared with a predetermined target value ψ ₀ of the strength of autocorrelation in step S12, which is executed immediately after step S11, and the If the value ψ is greater than ₀ , step S13 is executed, and if it is still smaller than the target value ψ ₀ , step S13 is executed.
14 will be executed immediately.

That is, in step S12, the fundamental period
If the autocorrelation strength ψi (T ₀ ) at T ₀ is larger than the target value ψ ₀ and it is determined that the secondary pulse wave signal sequence si (t) contains almost no noise,
In step S13, the secondary pulse wave signal sequence si
(t) is selected as the signal sequence for blood pressure measurement, and in the blood pressure value calculation routine of step S15, which is subsequently executed, the primary pulse wave signal sequence corresponding to the selected secondary pulse wave signal sequence si(t). (Pulse wave signal
A predetermined blood pressure value will be calculated based on the SM).

On the other hand, in step S12, the fundamental period T ₀
If it is determined that the autocorrelation strength ψi(T ₀ ) is smaller than the target value ψ ₀ and that the secondary pulse wave signal sequence si(t) still contains a lot of noise, the step In S14, the secondary pulse wave signal sequence si
It is determined which signal sequence (t) was created. That is, the secondary pulse wave signal sequence si(t)
If is the i-th created secondary pulse wave signal sequence indicated by the subscript i, that i is compared with a predetermined value, for example 100, and if i is still 100.
Until the above step S10 to S1 is reached,
2 will be repeated. However, in this case,
Secondary pulse wave signal sequence si created in step S10
(t) is different from all the secondary pulse wave signal sequences si(t) created before it, and its subscript i is also expressed as being incremented by one. Secondary pulse wave signal sequence si(t) compared in step S14
is the 100th one, that is, s ₁₀₀ (t), step S16 will be executed.

In step S16, the autocorrelation strength ψi(T ₀ ) at the fundamental period T ₀ obtained in step S11 is compared for the 100 types of secondary pulse wave signal sequences si(t) created so far. , among which the secondary pulse wave signal sequence si(t) with the largest autocorrelation strength ψi(T ₀ ) is determined, and in step S5, the set of determined pulse wave signals SM is selected from among the pulse wave signals SM stored in advance. A pulse wave signal corresponding to the secondary pulse wave signal sequence si(t) is selected. Based on the selected pulse wave signal, a predetermined blood pressure value is calculated in the subsequently executed step S15.

That is, the above-mentioned steps S14 and 16 are as follows.
The first pulse wave signal sequence SM contains a lot of noise, and it is difficult to create a secondary pulse wave signal sequence si(t) with a sufficiently large autocorrelation strength ψi(T ₀ ) at the fundamental period T ₀ . If not, or step S1
The target value ψ ₀ in 2 is high and the target value ψ ₀ is easily
This is provided for the purpose of shortening the computation time when a secondary pulse wave signal sequence si(t) having an autocorrelation strength ψi(T ₀ ) reaching ψi(T 0 ) cannot be obtained. The number of secondary pulse wave signal sequences si(t) to be compared can be determined as long as the calculation time allows, and each storage content including the secondary pulse wave signal sequence si(t) can be
As long as it is within the storage capacity of 16, it is desirable that the number be as large as possible; for example, as in this embodiment, about 100 is practically desirable.

As mentioned above, in step S15 executed after the end of step S13 or S16, each pulse wave signal SM corresponding to each pulse constituting the secondary pulse wave signal train selected in those steps S13 or S16 is A predetermined blood pressure value, for example, the systolic and diastolic blood pressure values are calculated based on The actual pressure P inside the cuff 2 when it increases is taken as the systolic blood pressure value,
Further, the pressure P when the pressure suddenly decreases is determined as the diastolic blood pressure value.

After completing step S15, the main program is immediately terminated.

As is clear from the above description, in this embodiment, the primary pulse wave signal sequence fundamental period determining means is executed in steps S8 and S9, and the secondary pulse wave signal sequence creating means is executed in step S10. ,
Furthermore, steps S11, S12, S13, S14
In step S, the secondary pulse wave signal sequence determining means
16 constitute a pulse wave selection means, and the blood pressure calculation routine of step S15 constitutes a blood pressure measuring means. In addition, steps S1 to S4, S6 and S7, the pump driving device 20 and the flow rate adjusting device 22 constitute a pressure control means for regulating the pressure P within the cuff 2.

According to this embodiment described above, the pulse wave signal SM
Regardless of the presence or absence of noise contained therein, highly accurate blood pressure values can be obtained in an extremely stable manner, and the practical effects are also significant.

That is, in this embodiment, when selecting a secondary pulse wave signal sequence containing almost no noise from among multiple secondary pulse wave signal sequences si(t), the basic period is
The autocorrelation strength ψi(t) of the secondary pulse wave signal sequence si(t) at T ₀ is compared with the target value ψ ₀ , and the target value ψ ₀
If there is a secondary pulse wave signal sequence with an autocorrelation strength ψi(t) exceeding , that secondary pulse wave signal sequence is selected for blood pressure measurement, or If the signal sequence is not created easily and the number of secondary pulse wave signal sequences si(t) reaches a predetermined number,
Among the predetermined number of secondary pulse wave signal sequences si(t), the strength of autocorrelation at the fundamental period T ₀ ψi(t)
A two-stage secondary pulse wave signal sequence selection method is adopted in which the one with the largest value is selected as the secondary pulse wave signal sequence for blood pressure measurement, which eliminates noise, shortens calculation time, and uses RAM 16 as a storage means. The structure is such that a reduction in the capacity of the blood pressure measuring device can be achieved extremely efficiently, and it is possible to sufficiently deal with practical problems such as operational aspects and cost aspects of a blood pressure measuring device.

In addition, the strength of autocorrelation at fundamental period T ₀ ψi
Even if (t) does not reach the target value ψ ₀ and the selected secondary pulse wave signal sequence is not as noise-removed as initially expected, the secondary pulse wave signal sequence si(t)
Considering that most of the noise has been removed in advance, the strength of autocorrelation at the fundamental period T ₀ of the selected secondary pulse wave signal sequence is the target value ψ ₀
It is easily recognized that the noise is sufficiently large, close to , and that noise has been removed to the extent that there is no problem in improving the accuracy of blood pressure measurement in practice.
However, in this case, in order to set it to a level that does not cause any practical problems, it is necessary to sufficiently consider the target value ψ ₀ and the number of secondary pulse wave signal sequences to be created, and the target value ψ ₀ is set to 0.9. As mentioned above, it is practically desirable to have about 100 in terms of the number and number of copies.

Although one embodiment of the present invention has been described above, it goes without saying that the present invention is not limited to this embodiment in any way.

For example, in the above embodiment, when determining the period T ₀ of the fundamental frequency ₀ of the primary pulse wave signal sequence SM, for the pulse wave signal SM consisting of all the pulse wave components and noise included in the primary pulse wave signal sequence SM, Considering a pulse of a predetermined width, the autocorrelation function was calculated for a pulse train consisting of such pulses and determined from its periodicity, but it is not necessary to consider the pulse train as described above, and each of the above pulse wave signals SM
The fundamental period T ₀ may be determined by considering a series of sine waves whose period varies between each pulse wave signal SM, and determining the autocorrelation function of such sine waves. Find the Fourier transform (Fourier spectrum) of a pulse train or sine wave,
The fundamental frequency ₀ may be obtained from the Fourier transform and the fundamental period T ₀ may be calculated.

Note that here, the Fourier transform is expressed as F()=∫ ^∞ _-∞ s(t)ε ^-j 〓 ^t dt, where the primary pulse wave signal sequence is s(t), and its maximum value is Since the value of T indicates the fundamental frequency ₀ , the fundamental period T ₀
can be obtained by finding its reciprocal ( _1/0 ).

Furthermore, when calculating the above autocorrelation function and Fourier transform, it is not necessary to calculate them over all the measured primary pulse wave signal sequences SM, but within the range where the fundamental period T ₀ can be calculated statistically with almost no error. If there is, it is possible to find the fundamental period T ₀ by simply finding it for a part of the primary pulse wave signal train consisting of a smaller number of pulse wave signals SM, and it can be determined at any time after the necessary information has been memorized. Well, any time is fine.

In addition, when creating the secondary pulse wave signal sequence si(t), in the above embodiment, adjacent pulse wave signals SM
A series of pulse trains was selected and created based on the interval T ₀ ±0.25T ₀ , but the above range is not necessarily limited to this and can of course be changed as necessary. be.

Furthermore, in the embodiment, the secondary pulse wave signal train
When selecting one from si(t), as mentioned above,
The limit on the number of signal sequences to be created is determined by both the target value ψ ₀ and the number of signal sequences i, and one secondary pulse wave signal sequence is selected from among the number of created signal sequences. Even if only one of them is adopted as a means for limiting the number of products to be produced, the object of the present invention can be achieved to a certain extent. Note that when selecting one secondary pulse wave signal sequence from the secondary pulse wave signal sequence si(t), it is not necessary to consider the strength of autocorrelation in the fundamental period T ₀ of the secondary pulse wave signal sequence si(t). There is no need to choose based on
The cross-correlation between each secondary pulse wave signal sequence si(t) and the primary pulse wave signal sequence may be calculated, and the one with the strongest cross-correlation may be selected.

In addition, the present invention is applicable not only to oscillometric type blood pressure measuring apparatuses but also to microphone type blood pressure measuring apparatuses, ultrasonic type blood pressure measuring apparatuses, and the like.

Note that when the present invention is applied to a microphone-type blood pressure measuring device, the Korotkoff sound as a pulse wave will be detected by the microphone, and the pressure sensor 4 will detect a pressure value signal representing the actual pressure P in the cuff 2. Only PV will be detected. In this case, the primary pulse wave signal train is a mixture of Korotkoff sounds and noise, and the secondary pulse wave signal train is created and selected with less noise mixed in with the Korotkoff sounds. and,
Furthermore, in such a microphone type blood pressure measuring device, the blood pressure measuring means (step S of the above embodiment)
In step 15), based on the selected secondary pulse wave signal sequence consisting of Korotkoff sounds with less noise as described above, the internal pressure of cuff 2 at the time corresponding to the first Korotkoff sound is determined to be the systolic blood pressure, and the last The internal pressure at the time corresponding to the Korotkoff sound is determined as the diastolic blood pressure.

In addition, in ultrasonic blood pressure measurement devices,
Ultrasonic waves emitted against the artery wall compressed by cuff 2 are subjected to Doppler displacement due to the vibrations of the artery, and the amount of displacement of the ultrasound waves that undergoes Doppler displacement is the primary pulse wave. It forms a pulse wave signal train, which contains noise. Therefore, in this case, noise other than the amount of Doppler change based on the vibration of the artery is removed, and as a result, a highly accurate blood pressure value based on normal vibration of the artery without noise can be obtained from a predetermined known known value. This can be determined using the following method.

The above-mentioned embodiments are merely examples of the present invention, and various modifications may be made to the present invention without departing from the spirit thereof.

[Brief explanation of drawings]

Fig. 1 is a diagram corresponding to claims of the present invention, and Fig. 2 is a diagram corresponding to claims of the present invention.
The figure is a block diagram showing an embodiment of the present invention applied to an oscillometric blood pressure measuring device, and FIG. 3 is a flowchart showing a program for explaining the operation of the device shown in FIG. It's a chat. 2: Cuff, 4: Pressure sensor (pulse wave sensor),
6: Pulse detector (pulse wave sensor), 14: CPU (processing unit), 16: RAM (storage means), 18:
ROM.

Claims (1)

[Scope of Claims] 1. A pulse wave signal processing device for removing noise contained in a pulse wave signal representing a pulse wave generated from an artery of a living body in synchronization with a heartbeat, which detects the pulse wave, a pulse wave sensor that outputs a pulse wave signal; a storage unit that sequentially stores the pulse wave signals detected by the pulse wave sensor; and a memory unit that sequentially stores the pulse wave signals detected by the pulse wave sensor; A series of primary pulse wave signal sequences with a period corresponding to the peak value interval is created, and the primary pulse wave signal sequence is subjected to Fourier transform processing or autocorrelation processing to determine the period of the fundamental frequency of the primary pulse wave signal sequence. a primary pulse wave signal sequence fundamental period determining means for determining the primary pulse wave signal sequence; and of each signal forming the primary pulse wave signal sequence,
a secondary pulse wave signal sequence creating means for creating a plurality of sets of secondary pulse wave signal sequences by selecting a signal having a period within a predetermined range centered on the period of the fundamental frequency; Determine the strength of autocorrelation in the period of the fundamental frequency of the set of secondary pulse wave signal sequences, respectively,
a secondary pulse wave signal sequence determining means for determining a set with the strongest autocorrelation among the plurality of sets of secondary pulse wave signal sequences; and a secondary pulse wave signal among the pulse wave signals stored in the storage means. A pulse wave signal processing device comprising: pulse wave selection means for selecting pulse wave signals corresponding to the set of secondary pulse wave signal sequences determined by the sequence determination means. 2. The pulse wave is a Korotkoff sound that is generated in synchronization with the heartbeat due to compression by the cuff when measuring the blood pressure of a living body using the cuff, and the pulse wave sensor includes a microphone that detects the Korotkoff sound. A pulse wave signal processing device according to claim 1. 3. The pulse wave is a pressure vibration generated within the cuff in synchronization with the heartbeat when measuring the blood pressure of a living body using the cuff, and the pulse wave sensor is connected to the cuff and measures the pressure within the cuff. The pulse wave signal processing device according to claim 1, which includes a pressure sensor that detects vibration and converts it into an electrical signal. 4. Claims in which the pulse wave is a pulsation of an artery wall that occurs in synchronization with a heartbeat, and the pulse wave sensor includes an ultrasonic sensor that detects the pulsation of the artery wall using ultrasonic waves. The pulse wave signal processing device according to item 1.