JPH0357428A - Pulsimeter - Google Patents

Abstract

PURPOSE:To remarkably improve the stability of a pulse display by providing a pulse wave pulse width evaluating means, valuating a pulse wave signal outputted from a pulse wave detecting circuit, and transmitting only a signal decided to be a normal pulse wave signal to a pulse arithmetic means. CONSTITUTION:A pulse wave signal detected by a pulse wave detecting circuit 1 is outputted to a pulse wave signal pulse width evaluating means 2. The pulse wave signal pulse width evaluating means 2 evaluates the pulse wave signal outputted from the pulse wave detecting circuit 1 with an evaluation reference determined by the number of pulses which a pulse arithmetic means 3 allows a display means 4 to display in the previous time and a reference frequency signal from a reference signal generating circuit 5. As a result of evaluation, in the case of the pulse wave signal having pulse width exceeding the reference, the pulse wave signal pulse evaluating means 2 transmits the input of the pulse wave signal to the pulse arithmetic means 3. The pulse wave arithmetic means 3 calculates the number of pulses per one minute from a period of the pulse wave signal transmitted from the pulse signal pulse width evaluating means 2, and outputs its result to the display means 4. Unless the signal exceeds some width, it is not decided to be the pulse wave signal, therefore, the display of the number of pulses by the display means 4 is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a photoplethysmometer. In particular, it concerns improving the stability of the pulse rate display. [Summary of the Invention] The present invention is directed to a pulse wave lance for detecting pulse waves in a photoplethysmography pulsometer that irradiates light to the capillaries of a fingertip or the like and detects the intensity of reflected light that changes depending on the pulsation as a pulse. The stability of the pulse rate display is improved by providing a pulse wave pulse width evaluation means between the output circuit and the pulse calculation means that measures the period of the pulse wave No. 3 and calculates the number of pulses per minute. This is what I did. [Prior Art] Various attempts have been made to stabilize the pulse display of portable pulse meters. However, most of them are
1-106130, JP-A-61106131, JP-A-6
As disclosed in No. 1-209634, etc., this was a method for processing calculated values when calculating the pulse rate per minute from the period of a pulse wave signal obtained by a pulse wave detection circuit. Here, as an example, a processing method called 4 data selection movement method will be explained. 4
The data selection movement method is to remove two from the maximum value and one from the minimum value among the four pulse rate conversion data, and display the remaining one data. A specific example is shown in FIG.

Figure 2 shows the operation when noise is present in the output of the pulse wave detection circuit. a, b, c, d, a in the diagram
, f are values converted into the number of pulses per minute from the average of the cycles of two consecutive pulse wave signals. As shown in FIG. 2, it can be seen that the displayed value is stable in response to discrete noises.

[Problem #s that the invention attempts to solve]

As mentioned above, it is effective against discrete noise. However, it is not effective against continuous noise. Third
The figure shows the operation when there is continuous noise. The output waveform of the pulse wave detection circuit in FIG. 3 is the same as that in FIG. 2 described above, but it appears to have no effect on continuous noise. This method of removing noise through data processing recognizes the noise as a pulse wave signal and performs arithmetic processing on it.
There are limits to the stability and accuracy of pulse rate displays.

[Means for solving intelligence problems]

In order to solve the above problems, the present invention focuses on the fact that pulses caused by noise are relatively narrow pulses, and the pulse wave detection circuit outputs an output signal between the pulse wave detection circuit and the pulse wave calculation means. A pulse wave pulse width evaluation means for evaluating the pulse width of pulse wave No. 3 was provided.

[Effect]

As described above, by providing a pulse wave pulse width evaluation means, evaluating the pulse wave signal output from the pulse wave detection circuit, and transmitting only the signal recognized as a regular pulse wave signal to the pulse calculation means, continuous Input noise can also be deleted, and the stability of pulse rate display can be greatly improved.

〔Example〕

Figure 1 shows a block diagram showing an embodiment of the present invention, and its operation will be explained. The pulse wave signal detected by the pulse wave detection circuit 1 is output to a pulse wave signal pulse width evaluation stage 2. The pulse wave signal pulse width evaluation means 2 uses the evaluation standard determined by the pulse rate previously displayed on the display 4 by the pulse calculation means 3 and the reference frequency signal from the reference signal generation circuit 5 to evaluate the pulse wave detection circuit l. Evaluate the output pulse wave signal. As a result of the evaluation, if the pulse wave signal has a pulse width greater than the reference, the pulse wave signal pulse width evaluation stage 2 transmits the input of the pulse wave signal to the pulse calculation means 3. The pulse calculation means 3 calculates the number of pulses per minute from the period of the pulse wave signal transmitted from the pulse wave signal pulse width evaluation means 2, and outputs the result to the display means 4. As mentioned above, by providing 1,000 stages of pulse wave signal pulse width evaluation, the pulse wave signal cannot be recognized as a pulse wave signal unless the signal has a certain width or more.
The pulse rate display on the display means 4 is stabilized. Next, the reason why a plurality of evaluation criteria for the pulse wave signal pulse width evaluation means 2 are prepared depending on the contents of the pulse calculation means 3 will be explained. In the case of photoplethysmogram detection, if the pulse wave detection circuit I is composed of an amplifier circuit, a filter, and a simple waveform shaping circuit, the results shown in FIGS.
As shown in the figure, the pulse width of the pulse wave signal changes depending on the pulse rate. When the pulse rate is high, the pulse width of the pulse wave signal is narrow, and when the pulse rate is low, the pulse width is wide. Therefore, if there is one type of evaluation standard for pulse wave signal pulse width evaluation 1,000 stages 2, it is necessary to set the evaluation standard to match the pulse width when the pulse rate is high. This will reduce the noise removal performance when the pulse rate is low. Therefore, in the present invention, the evaluation standard of the pulse wave signal pulse width evaluation means 2 is configured to change according to the level of the pulse rate.

Next, a first embodiment of the present invention is shown in FIG. 6, and its operation will be explained. FIG. 6 shows a detailed embodiment of the pulse wave signal pulse width evaluation means. Since the pulse wave detection circuit 1 and the pulse rate calculation means are commonly used, detailed diagrams are omitted. While the pulse wave signal pulse output from the pulse wave detection circuit 1 is "1", the reference frequency from the reference signal generation circuit 5, for example 128 Hz, is output from the AND gate 21. While the pulse wave signal pulse is “1”, inverter 2
Since the number of pinary counters consisting of T-type flimbu flops (hereinafter abbreviated as TFF) 23 to 27 is divided by M through 2, 128 of AND gate 21
TFFs 23 to 27 count the 11z output. AN
When the 128 11z output of the D game 21 is counted eight times, the Q output of the TFF 26 rises to "I". TFF2
The Q output of TFF 26 is connected to a differentiating circuit consisting of a D-type flimp flop C (abbreviated as DFF below) 30 and an AND gate 31, so at the moment the Q output of TFF 26 becomes "L", a certain width is generated. A pulse signal is generated at the output of AND gate 31. The pulse width of this pulse signal is DFF3
The reference signal generation circuit 5 to 256 is connected to the clock terminal C of 0.
Since llz is connected, No. 13 with a pulse width of 1.95 jo is generated. The time until a pulse is generated at the output of this division circuit is approximately 62.51I13 after the pulse wave signal is output at the output of the pulse wave detection circuit 1. The reason why this time is about 20 minutes is because the pulse wave signal output from the pulse wave detection circuit 1 and the signal from the reference signal generation circuit 5 are not synchronized. The error in the pulse rate that occurs due to the asynchrony is approximately ±6 when the pulse rate is around 210. One way to reduce this error is to increase the frequency of 128 Hz used by the AND gate 21 to a higher frequency. There are other methods, but since they are not directly related to the explanation of the present invention, this error will be ignored and the explanation will continue. After about 62.5n, a pulse is generated at the output of AND gate 31, and when the 128 Hz output of AND gate 21 is counted 8 times, the Q output of TFF 27 becomes "1".
Since the Q output of the TFF 27 is connected to a differentiating circuit consisting of the DFF 28 and the AND gate 29, the moment the Q output of the TFF 27 reaches "11", the A
A signal with a pulse width of 1.95 aa is generated at the output of the ND gate 29. The time until a pulse is generated at the output of this differentiating circuit is approximately 125 at after the pulse wave signal is output at the output of the pulse wave detection circuit l. Approximately 62.5 as mentioned above
The output of the AND gate 3I after m and the output of the AND gate 29 after about 125 ms are connected to a multiplexer connected to an ANDOR gate 33 and an inverter 32. The multiplexer outputs the output of the AND game }31 or 29 to the pulse rate calculating means 4 according to the control signal from the pulse rate calculating means 4. If the previous calculation result of the pulse rate calculation means 4 is a pulse rate of 100 or less, the control signal is "l", 10
If the pulse rate calculation means 4 is configured so that the pulse rate is "O" when the pulse rate is 0 or more, the pulse rate calculation means 4 will be configured so that when the pulse rate is 100 or less,
Pulse calculation is performed when a pulse wave signal with a pulse width of approximately 125 m or more is input. Further, when the pulse rate is 100 or more, pulse calculation is performed when a pulse wave signal having a pulse width of about 62.5ffi or more is input. As described above, by providing the pulse wave pulse width evaluation means 2 between the pulse wave detection circuit l and the pulse calculation means 4, it is possible to calculate the pulse using a pulse wave signal having a certain pulse width or more. Become. As a result, noise with a narrow pulse width is ignored, making it possible to stabilize the pulse rate display. In addition, in this example, there are two types of pulse width evaluation reference values for the pulse wave signal, but
It is easy to increase this further. By doing so, the noise removal performance can be further improved. or,
There is a concern that if a long evaluation criterion is applied when the pulse rate is high, that is, when the pulse width of the pulse signal pulse is relatively narrow, measurement may become impossible. However, this problem can be easily solved by selecting the evaluation reference value and the reference value, and is not a drawback of the present invention at all.

For example, when it becomes difficult to obtain a pulse, there is a method in which the minimum evaluation reference value is automatically selected.

Next, another embodiment of the present invention will be shown and its operation will be explained. A case will be described in which the above-mentioned pulse wave signal pulse width evaluation means and pulse rate calculation means are attempted to be realized by software processing of a microprocessor. Figure 7 shows a flowchart when the pulse wave signal pulse width evaluation means and pulse calculation means are implemented using software. An interrupt occurs when the pulse wave signal rises, and the software starts. First process STEP 1
Now, change the signal level of the pulse wave signal pulse and set it to “H”.
If so, proceed to STEP 2. In STEP 2, it is checked whether the previous pulse rate display was 100 or more or 100 or less. As a result of checking, if it is less than 100,
Let the pulse wave signal pulse width evaluation value be a. If it is 100 or more, the pulse wave signal pulse width evaluation value is set as b. In the next STEP 4, add +l to the H counter. Next STEP 5
Then, compare whether the contents of the H counter are equal to the predetermined pulse wave signal pulse width evaluation value, and if they are equal, ST
In EP6, call the pulse calculation subroutine and calculate the pulse rate i.
*Do x. If they are not equal, the process returns to STEPI and the loop from STEPI to STEP5 is repeated until the value of the H counter becomes equal to the predetermined pulse wave signal pulse width evaluation value. During this time, when the pulse wave signal pulse falls and becomes "L", the H count is cleared and LHALT is performed in STEP7.

With the processing described above, pulse calculation cannot be performed unless the pulse wave signal has a certain width or more. As a result, noise with a narrow pulse width is ignored, making it possible to stabilize the pulse rate display.

〔Effect of the invention〕

As described above, according to the present invention, the pulse wave No. 4g pulse width evaluation means for evaluating the pulse wave signal output from the pulse wave detection circuit removes noise and transmits only the original pulse wave signal to the pulse calculation means. This makes it possible to greatly improve the stability of pulse rate display.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing an embodiment of the present invention.
Figure 3 is a diagram showing the operation of the data selection movement method. Figure 3 is a diagram showing the operation of the 4-data selection movement method when there is continuous noise. Figure 4 is the waveform of the pulse wave detection circuit when the pulse rate is low. , FIG. 5 is a diagram showing the waveform of the pulse wave detection circuit when the pulse rate is high, FIG. 6 is a diagram showing the first embodiment of the present invention, and FIG. 7 is a diagram showing the second embodiment of the present invention. It is a flowchart explaining an example. Pulse wave detection circuit Pulse wave signal pulse width evaluation means Pulse calculation means Display means Reference signal generation circuit or higher

Claims (1)

[Claims] A photoplethysmogram type pulsometer includes a pulse wave detection circuit for detecting a pulse wave, a pulse wave signal pulse width evaluation means for evaluating a pulse width of a pulse wave signal output from the pulse wave detection circuit, and the pulse wave signal. At least a pulse calculation means for measuring the time interval of pulse wave signal pulses evaluated by the pulse width evaluation means and recognized as a pulse wave signal, and calculating the number of pulses per minute,
A pulse meter characterized in that the evaluation reference value of the pulse wave signal pulse width evaluation means changes according to the pulse rate calculated by the pulse rate calculation means.