JPH0255035A - Acceleration pulse wave gauge - Google Patents

Abstract

PURPOSE:To easily evaluate the state of blood circulation clinically based on the shape of the secondary derivative curve of a finger tip end volume pulse wave curve by controlling the brightness of a light source with the output of a photoelectric converter so that the basic resistance of the photoelectric converter is invariably near the fixed value. CONSTITUTION:The detection section D of the pickup section of a volume pulse wave gauge contains a lamp L provided oppositely to a recess to be inserted with a finger tip end and a light detector made of a photoelectric element such as CdS, this photoelectric element R3 forms a bridge together with resistors R1, R2, R3' and R4. The output of a bridge circuit is amplified and outputted by a differential amplifier, the brightness of the lamp L is controlled by a switch S operated by a control circuit so that this bridge is almost balanced. The secondary differential of the output E1 of the pickup section is determined by a differentiation circuit and displayed, the evaluation of the state of blood circulation is facilitated by normalizing and comparing the voltage at points (b), (c) and (d) of the secondary derivative curve of the volume pulse wave.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an acceleroplethysmometer for clinically evaluating the state of blood circulation function from the shape of a second derivative curve of a volume pulse wave curve.

(Prior Art) Conventionally, volume pulse waves have been considered as one method for evaluating blood circulation, and various methods for evaluating the waveform of the volume pulse wave curve obtained by a volume pulse wave meter have been discussed. The evaluation method focuses on the height of the amplitude of the waveform of the plethysmographic curve, and in order to avoid the influence of peripheral skin temperature, the test subject is kept at a constant room temperature at appropriate times, and the temperature calibration circuit is was considered necessary. Furthermore, it was considered an absolute requirement that the light source of the photoelectric converter of the pulse wave meter used for this measurement maintain a constant brightness. This situation has not changed even in the case of an acceleroplethysmometer in which blood circulation is evaluated by obtaining the second derivative curve of the volume pulse wave curve. Therefore,
In these measuring instruments, when a variable resistance element is used on one side of the bridge circuit, the resistance opposite to it is changed to remove the direct current component of the electrical signal obtained from the bridge circuit.

(Problems to be Solved by the Invention) The present inventor has previously discovered that the waveform of the second derivative curve of the volume pulse wave curve, especially the relative size of its categorical value, has a decisive meaning in the evaluation of blood circulation. (Japanese Unexamined Patent Publication No. 57-93036).

Based on this discovery, the present invention provides a means for collecting an original fingertip plethysmography curve so that it can be efficiently and accurately differentiated in order to draw a second derivative curve of the fingertip plethysmography curve. The object of the present invention is to provide an acceleroplethysmometer equipped with means for clinically facilitating the evaluation of the state of blood circulation from the shape of the second derivative curve of the volume pulse wave curve.

(Structure of the Invention) The acceleroplethysmometer of the present invention includes a light source that illuminates a capillary bed portion of a fingertip or an ear lobe, and a light-resistance photoelectric converter that detects the intensity of light transmitted through the capillary bed portion. , an information processing device for calculating a second derivative curve of the output of the photoelectric converter,
The brightness of the light source is controlled by the output of the photoelectric converter so that the basic resistance of the photoelectric converter is always near a constant value.

The photoelectric converter includes a light-receiving element whose resistance value changes depending on the intensity of transmitted light whose intensity changes depending on the change in the amount of metal in the capillary bed, and most commonly, a bridge circuit using this element as a component. It consists of an amplifier that amplifies the electrical signal obtained from this light receiving element or a bridge circuit including it, a two-time differentiator circuit, an A/D converter, an information processing control device using a microcomputer, and a display recorder for displaying and recording information obtained from these. ,
It is equipped with peripheral devices that perform storage, etc.

In this invention, since the relative wave height of the extreme value of the second derivative curve of the volume pulse wave is a problem, the reference zero level is not the output when the input is zero, but when the DC signal is input. This is the output when the Further, the information processing device may include a circuit for determining which level the extreme value or inflection point of the measured waveform belongs to when the highest value of the negative level is detected and the highest value is divided into a plurality of voltages. This allows the waveform to be automatically evaluated and displayed.

Furthermore, it is easy to indicate that measurement is impossible based on the pulse wave height, ripple number, etc., and to numerically display the relative size of the extreme value or inflection point of the waveform.

(Function) The basic function of blood circulation is to supply nutrients and oxygen to human body cells and remove waste products, and this function is generally carried out by capillaries6. Therefore, the quality of blood circulation in capillaries depends on the quality of blood circulation. This is a problem, and blood pressure and other factors are only one of the indicators that indirectly indicate whether the condition is good or bad.

As mentioned above, the present inventors have found that the best way to know the state of the blood '#i ring is to look at the waveform of the second derivative of the volume pulse wave. In other words, as shown in Fig. 3, when the stroke volume is large, the trough falls significantly with respect to the wave height a, which indicates the start of blood vessel expansion. When blood is pooled and venous return becomes poor and blood cannot be returned sufficiently to the left heart, the stroke volume decreases and the drop in b becomes less. When venous contraction is moderate and venous return is good, peak C rises near or beyond the baseline, but as venous contraction worsens, peak C rises.
will no longer rise. The valley d indicates the degree of burden on the left heart, and if the burden is heavy, such as in a person involved in strenuous sports or a bedridden elderly person, the valley d will descend and the heart will also enlarge.

When using a photoelectric transducer that utilizes resistance changes caused by light that passes through the m-tip and changes in intensity depending on the amount of metal to measure fingertip plethysmography, a resistor bridge circuit is used. However, as mentioned above, in the past, emphasis was placed on the peak value, so the brightness of the light source was kept constant.

However, the light transmittance varies greatly for each specimen. For example, when the hands are cold, when a person has thin fingers, when a newborn baby, etc., the difference from the standard case becomes extremely large. Therefore, if the brightness of the light source is kept constant, the output level will vary depending on the sample. Conventionally, the DC component coming out of the bridge circuit is removed by changing the resistance corresponding to the resistor group in which the light receiving element is included.

In contrast, in the present invention, as described above, the absolute value of the wave height of the fingertip volume pulse wave curve is not evaluated, so there is no need to keep the brightness of the light source constant.

In addition, using an area with high resistance has the advantage of suppressing noise caused by heat to a low level, so by controlling the brightness of the light source with a microcomputer at the beginning of measurement, the value of the resistance group including the photodetector can be adjusted. By setting the bridge to a balanced state and then collecting the fingertip plethysmogram, it is possible to extract only the part of the waveform that contains the necessary information (depending on the brightness of the light source). However, the resistance value that changes in response to changes in blood content is usually around 2-3% of the resistance value when a finger is inserted.)

Moreover, this eliminates the need to strictly control the brightness of the light source, simplifies the device, and facilitates maintenance.

Furthermore, if a bridge is not constructed and the resistance value of the light receiving element is directly used as an output signal, this method is extremely effective since the DC component cannot be removed by the bridge circuit as described above.

In addition, in this invention, since the relative wave height of the extreme value or inflection point of the second derivative curve of the volume pulse wave is a problem,
In addition to displaying a line of zero acceleration as a standard for evaluation, this standard line and the maximum minus extreme value are divided into an appropriate number of equal parts, and an information processing device is used to create an office work evaluation circuit based on where the extreme value or inflection point is. Include in

(Example) Examples of this invention will be shown below.

FIG. 1 shows a volume pulse waveform pickup section of the present invention.

The detection section includes a photodetector consisting of a lamp L and a photoelectric element such as CdS, which is provided oppositely in the four parts into which the fingertip is inserted, and this photoelectric element R3 has resistors R, R2, R, ,R
4 and form a bridge.

The output of the bridge circuit is amplified and outputted by a differential amplifier, and the brightness of the lamp is controlled by a switch S operated by a control circuit (not shown) so that the bridge is approximately balanced.

The second derivative of the output E0 of the pickup section is obtained by a differentiating circuit and displayed, but the above-mentioned evaluation of the quality of the blood circulation can be done using the second derivative curve of the volume pulse wave shown in Figure 3. It will be easier to compare by normalizing the voltages at points No. 3, C, and D. For standardization, b, c,
For example, if the maximum value (looking in the negative direction) of points d is 3,
Checking in which region the values at points b, c, and d are located.

It becomes possible to categorize the waveform of the second derivative curve of the fingertip plethysmogram. An example of a specific configuration of the office work evaluation circuit will be explained with reference to FIG.

The output from FIG. 1 is introduced into the input terminal IP of the amplifier 1, and the waveform a is sufficiently amplified. Reference numeral 2 denotes a circuit that clips the voltage above the reference voltage E and performs waveform shaping, in which noise is removed and the waveform a is shaped into a rectangular wave. The output is differentiated by a differentiating circuit 3, and a negative differential pulse is obtained by a rectifying circuit 4. Therefore, the obtained differential pulse corresponds to the zero crossing point between point a and point b. 5 is a one-shot multi and is triggered by the output of the differentiating circuit 4. The output square wave is T. It has a time width of

T is used to obtain the time including the zero cross point, c, and d, but it is sufficient if the time is set to be longer. Therefore, one hour Tl1l may be constant, but it can be made variable in response to individual differences in pulse time, and can be set as appropriate. Reference numeral 6 denotes a gate circuit that allows a signal from the input terminal IP to pass through for a period of time T0. 7.8 is a differentiating circuit, which provides a second-order differentiated output of the input signal. The second derivative output detects a temporal change in the electrical output of the second derivative.

Therefore, the maximum point, minimum point, and inflection point in the input signal can be detected, and points b, c, and d can be known. In addition, in order to detect that point C of type F and G in Fig. 3 appears as an inflection point, a circuit that takes the third derivative may be added. 9 is a waveform shaping circuit, b, c, d The sampling pulse at the time point is output. 10 is a delay circuit τ, which will be described later. Reference numeral 11 denotes a sampling circuit, which samples the input signal using the output of the waveform shaping circuit 9 as a sampling pulse and stores it in the sequential storage circuit 12. Memory circuit 12 receives addressing by sampling pulses.

Three addresses can be specified from the zero cross point. Reference numeral 13 denotes a maximum value detection circuit which stores the maximum value among the voltages at points b, c, and d. The output of the maximum value detection circuit 13 is divided by a voltage dividing circuit 14. If each resistance of the voltage divider circuit is set to the same value, E2 will be 2/3 of the maximum value E1, E,
has a value of 1/3.

Reference numeral 15 denotes a pulse-hydraulic analyzer, into which the voltage E2, E of the voltage dividing circuit 14 is introduced into the comparison voltage. 16
is a control circuit that sequentially controls the voltages corresponding to points A, C, and D in the memory circuit 12 to the pulse hide analyzer 1.
This is for inputting data to 5. Therefore, the voltages at points c, d are normalized at the output terminal ○P of the pulse hide analyzer 15 (for example, c/b, d/b, or b/a, c/a, d/a, etc. as necessary). ) can be obtained. This standardized wave height can also be displayed numerically as it is.

Note that the above-mentioned delay circuit 10 has a sampling time difference due to the time lag in the differentiating circuit.c.

This is to correct the deviation from point d, but it is not necessarily necessary. The above circuit can also be digitized using an AD converter.

In this case, the delay circuit can be easily realized by using a shift register or the like.

A sine-pulling pulse is detected in one pulse without using a delay circuit, this is stored, and the signal of the second derivative curve of the next pulse is sampled based on the sampling pulse and stored in the storage circuit 12. You can.

When observing the second derivative curve of the fingertip plethysmogram, b, c,
The position of point d (white value or inflection point of the curve) has an important meaning, but when observing these points, the line with zero change acceleration and the evaluation partial pressure line obtained by the above voltage dividing circuit 14 are used. By writing them in parallel, it becomes easier to understand them all.

Normally, in information processing equipment, this zero position sets the level of the signal input O to potential 0, but if the offset adjustment of the system system is insufficient or the potential remains in the A/D converter, for example, In the case of an 8-bit A/D converter, the ideal position is 128 bits, but the position may be shifted up or down by several bits. Therefore, in the device of the present invention, the DC signal (change acceleration O
The potential when the signal) was input was set to 0. This can be obtained from input without inserting the fingertip into the pickup section prior to the start of measurement.

This output OP can be displayed by determining which pattern of A to G in FIG. 3 it belongs to using a microcomputer or the like. A flowchart of the determination procedure is shown in FIG. In the figure, P, Q, and R indicate to which evaluation partial pressure zone the standardized wave heights at points b, c, and d belong, respectively.

If (PR)>O, that is, point b is deeper than point d, the waveform belongs to either A to D. Among them, Q≦O, that is, C
If the point is greater than zero and has a different sign from point b, it is determined to be type A. Also.

If (P-Q)>O, that is, point C is sufficiently higher than point b, it is type B, and if (P-Q)=0, that is, they belong to the same partial pressure zone, it is type D.

If (P-R)=O, that is, point b and point d belong to the same partial pressure zone, and (P-Q)>O, it is determined to be type C, otherwise it is determined to be type D.

If (P-R)>O, then E type if (P-Q)>O, F type if (P-Q)=O, and (P-R)
<O, it is determined to be C type.

The chart of this judgment method corresponds to the pattern classification shown in FIG. 3, but it can be easily extended to the case where the classification is further subdivided.

In addition, it is difficult to collect a fingertip plethysmogram curve when the fingers are cold and the skin blood vessels are constricted, or when one finger is damaged and there is extremely little change in blood content in the capillary bed. ,
Therefore, it is difficult to collect the accelerated pulse wave, which is the second derivative curve. For this reason, in the apparatus of the present invention, if the wave height of the fingertip plethysmogram is below a certain value, it is determined that it is difficult to test the accelerated plethysmogram.

Along with that fact, instructions based on the instruction manual are displayed. In addition, the number of ripples is 2 per minute which is considered difficult to test.
When it is 5 or less, there is a case where the noise is large.

(Effects of the Invention) The accelerometer of the present invention superimposes and displays the reference line for judgment on the waveform of the accelerating pulse wave as described above, thereby detecting the extreme values or inflection points a and b of the waveform. The coordinates of points , c, and d are now clear, and the accelerated pulse waves A, B, C, D, E,
It is easy to determine which waveform (F or G) it belongs to, or even if it belongs to the same waveform, whether it is close to a waveform that indicates a good direction or a waveform that is close to a bad direction, and even those without specialized knowledge can understand blood circulation. It becomes possible to evaluate whether the condition is good or bad.

Furthermore, by converting the coordinates of points a, b, c, and d into numerical values and comparing them, it is possible not only to observe the changes in detail, but also to be automatically evaluated by the instrument.

Thereby, even a person with little specialized knowledge can operate this device and easily evaluate the quality of blood circulation.

[Brief explanation of the drawing]

Figure 1 shows a part of the pink-up part of the accelerometer of this invention.
2 is a circuit diagram showing an example of an evaluation circuit for the extreme value or inflection point value, FIG. 3 is a pattern diagram of the obtained acceleration pulse waveform, and FIG. 4 is a diagram of the pattern judgment. It is a flowchart showing a procedure. D: Detection section L: Lamp S: Suinochi 2: Waveform shaping circuit 3, 7, 8: Differential circuit 5: One shot multi 6: Gate circuit 9: Waveform shaping circuit 10: Delay circuit 11: Sampling circuit 12: Memory circuit 13 : Maximum value detection circuit 14: Voltage dividing circuit 15: Pulse height analyzer 16 Two control circuits

Claims (1)

[Scope of Claims] 1) A light source that illuminates a capillary bed portion of a fingertip or ear lobe, a light-resistance type photoelectric converter that detects the intensity of light transmitted through the capillary bed portion, and a photoresistance type photoelectric converter that detects the intensity of light transmitted through the capillary bed portion. It consists of an information processing device that calculates the second derivative curve of the output, and the brightness of the light source is controlled by the output of the photoelectric converter so that the basic resistance of the photoelectric converter is always near a constant value. Characteristic accelerometer plethysmometer 2) In displaying the second derivative curve of the blood content collected from the fingertip or ear tip, a line of zero change acceleration is drawn in parallel to facilitate clinical evaluation of the waveform. 3) The information processing device detects the negative maximum value of the second derivative of blood content, and divides the detected value into a plurality of equal parts. 4) Fingertip acceleroplethysmometer according to claim 1, comprising a circuit that automatically determines to which level the extreme value or inflection point of the second derivative belongs. Or, when clinically evaluating the state of blood circulation from the shape of the second derivative curve of the change in the blood content of the ear flap,
Detects whether the specimen is in a condition that can be tested correctly,
The acceleroplethysmometer according to claim 1, which displays instructions to the operator when the test is difficult.