Biological signal measurement device, biological signal measurement system, biological signal measurement method, biological signal measurement program, and recording medium

Abstract

To solve the problems with a conventional biological signal measurement device that even when attempting to compress a biological tissue and measure a capillary re-filling time, there can be a case where sufficient compression is not applied to the biological tissue and blood is not removed, a case where positional relationships of sensor elements and compression directions are not aligned, and the like, that in a change in transmission light intensity obtained in such cases, there is a possibility of the obtained capillary re-filling time being inaccurate, and that a user of the biological signal measurement device needs to determine whether or not the measurement of a capillary re-filling time is performed appropriately from measurement results and the like.SOLUTION: A biological signal measurement device includes an information processing part for calculating a capillary re-filling time after a compressing period in which a biological tissue is compressed on the basis of a variation in the intensity of received light received by a light reception part for receiving light that is emitted from a light emission part and transmitted through the biological tissue. The information processing part determines whether or not the variation in the intensity of received light is appropriate for the calculation of the capillary re-filling time using the intensity of received light.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a biological signal measurement device, a biological signal measurement system, a biological signal measurement method, a biological signal measurement program, and a recording medium.

Background Art

[0002] As a method for observing a patient's condition, there is a method of measuring capillary refilling time. Capillary refilling time is the time until the redness recovers after compressing and then releasing the nail bed, and it becomes longer when there is a problem with blood circulation. The judgment regarding circulation based on capillary refilling time is also used in triage.

[0003] Patent Document 1 describes a biological signal measurement device capable of selecting a pulse oximeter mode for calculating oxygen saturation and the like, and a capillary refilling time measurement mode for calculating capillary refilling time. The biological signal measurement device is attached to a subject's living tissue. And it includes a light emitting unit that irradiates light on a sensor attachment part such as a fingertip which is the subject's living tissue, and a light receiving unit that outputs an electrical signal according to the received light intensity of the light.

[0004] The light from the light emitting unit in the above-described biological signal measurement device passes through the living tissue having blood in the capillaries and enters the light receiving unit. And when the living tissue is compressed, blood is excluded from the capillaries of the living tissue, the light absorption by the blood decreases, and the transmitted light intensity increases. Then, as the blood reflows into the living tissue of the sensor attachment part after the compression is released, the light absorption by the blood increases and the transmitted light intensity decreases. The time from when the compression is released until the transmitted light intensity reaches a predetermined value is the refill time.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, even when attempting to measure the capillary refill time by compressing the living tissue, there may be cases where sufficient compression is not applied to the living tissue and blood is not expelled, or cases where the positional relationship and compression direction of the sensor element are not aligned. In such cases, the capillary refill time obtained from the change in the transmitted light intensity may be inaccurate. And whether the measurement of the capillary refill time is appropriately performed has to be judged by the user of the biological signal measuring device based on the measurement results and the like.

Means for Solving the Problems

[0007] A biological signal measuring device according to an embodiment of the present invention includes an information processing unit that calculates a capillary refill time after a compression period during which the living tissue is compressed, based on fluctuations in the received light intensity received by a light receiving unit that receives light irradiated from a light emitting unit and transmitted through the living tissue. The information processing unit is characterized in that it uses the received light intensity to determine whether the fluctuations in the received light intensity are appropriate for calculating the capillary refill time.

Advantages of the Invention

[0008] It is possible to determine whether the wearing state is appropriate for calculating the capillary refill time without burdening the user of the device.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0010] Fig. 1 shows a biological signal measurement system according to an embodiment of the present invention. The biological signal measurement system includes a biological signal acquirer 2 for acquiring a biological signal, and a biological signal measurement device 1 connected to the biological signal acquirer 2 for measuring the capillary refill time CRT and the like.

[0011] The biological signal acquirer 2 of the embodiment includes a sensor device 21 and a support tool 22 for applying pressure to the biological tissue. The sensor device 21 includes a light emitting part 211, a light receiving part 213, and wirings 212 and 214 respectively connected thereto. In Fig. 1, the light emitting part 211 is attached to the nail N of the finger F, and the light receiving part 213 is attached to the finger pad B. The light emitting part 211 and the light receiving part 213 are wound around the finger F with a tape (not shown) and fixed thereto. The support tool 22 covers from the outside of the light emitting part 211 and the light receiving part 213 to compress or release the compression of the biological tissue. Note that the biological tissue can also be manually compressed without using the support tool 22.

[0012] The support device 22 has a lid 221 attached to a support 224 via a hinge portion 225 so as to be openable and closable. The support device 22 is provided with a bag film 222 on the side of the finger F in a pressure chamber 221a of the lid 221 to which a tube 223 is connected. The lid 221 and the bag film 222 of the support device 22 form a bag body surrounding the pressure chamber 221a. Further, the support device 22 has a support 224 extending from the tip side of the finger F to the lower side of the finger pad B. The support 224 also extends to the side portion of the finger F. The outside of the finger F is surrounded by the support 224, the bag film 222, the lid 221, and the hinge portion 225. FIG. 1 shows a cross section of the support device 22 in a mounted state in which the finger F is inserted into a recess surrounded by the support 224, the bag film 222, etc. The support device 22 compresses the finger F, which is a living tissue, from the outside.

[0013] On the other hand, the biological signal measurement device 1 includes a processing unit 11, a storage unit 12, a pressure generation unit 13, a light emission output unit 14, a light reception input unit 15, a switch input unit 16, and a result output unit 17. The pressure generation unit 13 generates air pressure and supplies it to the tube 223. Further, the light emission output unit 14 causes the light emission unit 211 to emit light by supplying current to the wiring 212. The light irradiated from the light emission unit 211 passes through the living tissue and is received by the light reception unit 213. When the light passes through the living tissue, absorption, reflection, etc. of the light occur in the living tissue, and finally a part of the transmitted light reaches the light reception unit 213. Then, the light reception input unit 15 receives the voltage corresponding to the light reception amount received by the light reception unit 213, digitizes it, and sends it to the processing unit 11. The switch input unit 16 has an inspection switch 161. When the inspection switch 161 is operated, the biological signal measurement device 1 calculates the capillary refill time CRT. Note that the inspection switch 161 in the embodiment is a physical switch, but it may be something like a button displayed on a display device having an input function by contact. The processing unit 11 calculates the capillary refill time CRT after the compression period during which the living tissue is compressed from the outside based on the fluctuation of the light reception intensity received by the light reception unit 213. When it is determined that there is a blood circulation abnormality based on the calculation result, the circulation abnormality information is output from the result output unit 17 and notified to the user by a voice generation device, a display device (not shown), etc. The control of these biological signal measurement devices 1 is performed by the processing unit 11 which is an information processing unit.

[0014] When evaluating the blood circulation state, the air generated by the pressure generating unit 13 of the biological signal measuring device 1 is supplied to the pressure chamber 221a of the support tool 22 via the tube 223. The pressure generating unit 13 and the processing unit 11 that controls the pressure generating unit 13 function as an automatic compression device that automatically compresses to form a compression period. The pressurization target value and the compression time are stored in the storage unit 12, and the pressure in the pressure chamber 221a is adjusted by the air pressure generated from the pressure generating unit 13 according to the stored pressurization target value and compression time. Then, as the air pressure in the pressure chamber 221a of the support tool 22 increases, the bag film 222 expands in the direction of the claw N to compress the finger F from the outside. Due to the compression, the blood volume in the capillaries of the finger F, which is a biological tissue, decreases. The light used by the sensor device 21 uses a wavelength with a high absorption rate by blood. Therefore, when the blood volume of the biological tissue through which the light passes decreases, the absorption of light by the blood decreases and the transmitted light intensity I increases. The transmitted light intensity I is the received light intensity that is sent out from the light emitting unit 211 and obtained by the light receiving unit 213 for the light transmitted or reflected by the biological tissue, and varies depending on the increase or decrease in the blood volume of the biological tissue.

[0015] Then, after a predetermined compression period has elapsed, the pressure is released by the pressure generating unit 13 of the biological signal measuring device 1. Then, the expansion of the bag film 222 in the direction of the claw N disappears, and the compression of the finger F is released. As a result, blood returns to the capillaries of the biological tissue, the absorption of light by the blood increases, and the transmitted light intensity I decreases. In the biological signal measuring device 1, the transmitted light intensity I is digitized by the light receiving input unit 15, and the processing unit 11 calculates the capillary refill time CRT at which the transmitted light intensity I becomes smaller than a predetermined value Ir. When the capillary refill time CRT is longer than a predetermined time, circulation abnormality information indicating that there is a blood circulation abnormality is transmitted from the result output unit 17, and it is notified that there is a blood circulation abnormality.

[0016] Using the graph of the transmitted light intensity change, which is the change in the transmitted light intensity I in Fig. 2, the measurement of the capillary refill time CRT will be described. The vertical axis in Fig. 2 indicates the amount of light received by the light receiving unit 213, which is the transmitted light intensity I, the light intensity after the light emitted by the light emitting unit 211 passes through the biological tissue of the finger F and is the received light intensity. The horizontal axis indicates the elapsed time. The compression of the finger F starts at the compression start time Ps and is released at the compression release time Pr. Before the compression start time Ps of the finger F, since the blood volume of the biological tissue is large, the transmitted light intensity I is small. During this period, pulsations can be seen in the transmitted light intensity I.

[0017] At the compression start time Ps, when the air pressure in the pressure chamber 221a is increased by the air sent from the biological signal measuring device 1 and the finger F is compressed by the assisting tool 22, the blood volume of the biological tissue decreases and the light absorption decreases. Therefore, the transmitted light intensity I received by the light receiving unit 213 increases. In Fig. 2, the compression starts at the compression start time Ps, and the compression is released at the compression release time Pr about 6 seconds after that. The period from the compression start time Ps to the compression release time Pr is the compression period Ps-Pr. During the compression period Ps-Pr, unlike before the compression start time Ps, the pulsation of the transmitted light intensity I is almost absent.

[0018] After Pr at the time of pressure release, the transmitted light intensity I decreases and becomes the same transmitted light intensity I as that at Ps at the start of pressure. In the embodiment, the time for the transmitted light intensity I to decrease to a predetermined value Ir after Pr at the time of pressure release is defined as the capillary refill time CRT. The fact that the transmitted light intensity I has decreased to the predetermined value Ir indicates that the redness has recovered in the biological tissue of the finger F. When the capillary refill time CRT is equal to or more than a predetermined number of seconds, circulation abnormality information is transmitted from the result output unit 17, and it is notified that there is a blood circulation abnormality. Note that the predetermined value Ir may be stored in the storage unit 12 of the biological signal measurement device 1 as a fixed value set in advance, or may be calculated using the transmitted light intensity I before Ps at the start of pressure or immediately before Pr at the time of pressure release. Further, the predetermined value Ir may be calculated using the amount of change in the transmitted light intensity I due to pressure. For example, the predetermined value Ir may be a value obtained by adding a predetermined rate (e.g., 10%) of the transmitted light intensity change amount Ic, which is the difference between the transmitted light intensity I at Ps at the start of pressure and the transmitted light intensity I at Pr at the time of pressure release, to the transmitted light intensity I at Ps at the start of pressure. Further, the predetermined value Ir may be a value at which the rate of change of the transmitted light intensity I after Pr at the time of pressure release becomes a certain value or less.

[0019] However, even when trying to calculate the capillary refill time CRT by compressing the biological tissue, there may be cases where sufficient pressure is not applied to the biological tissue and blood is not expelled, or the positional relationship and compression direction between the light emitting unit 211 and the light receiving unit 213 do not match. In such cases, in the change in the transmitted light intensity I obtained, the obtained capillary refill time CRT may be inaccurate.

[0020] <When pressure is insufficient> When the finger F is small or the lid 221 of the support tool 22 is not fixed in the closed state, etc., and the pressure on the finger F is insufficient, it is not possible to detect an abnormality in blood circulation based on the capillary refill time CRT. If the change in the transmitted light intensity I has any of the following two characteristics, there may be insufficient pressure on the biological tissue. (1) Pulsation is observed during the compression period Ps-Pr from Ps at the start of compression to Pr at the time of pressure release. (2) The change amount Ic of the transmitted light intensity, which is the change amount of the transmitted light intensity I due to compression, is small. Fig. 3 shows a graph of the change in the transmitted light intensity, which is the change in the transmitted light intensity I when the compression on the finger F is insufficient. Fig. 2 shows the change in the transmitted light intensity I when the compression is sufficient. The determination of insufficient compression will be described with reference to Figs. 2 and 3.

[0021] (1) Determination of insufficient compression due to residual pulsation When pulsation is observed during the compression period Ps - Pr, it is determined that the compression is insufficient. Specifically, the waveform of the transmitted light intensity I during the compression period Ps - Pr from the start of compression Ps to the end of compression Pr shown in Figs. 2 and 3 is passed through a band - pass filter. If the output is equal to or greater than a predetermined value, it is determined that it is inappropriate for calculating the capillary refill time CRT. The pass - band of the band - pass filter is set to the frequency at which the heartbeat can occur. In the waveform of the transmitted light intensity I during the compression period Ps - Pr in Fig. 2, no pulsation of the frequency component of the heartbeat is observed, so the output does not reach the predetermined value and no pulsation is detected. On the other hand, in the waveform of the transmitted light intensity I during the compression period Ps - Pr in Fig. 3, pulsation of the frequency component of the heartbeat is observed. Therefore, when the output reaches the predetermined value, pulsation is detected and it is determined that the compression is insufficient.

[0022] The band - pass filter in this embodiment is provided as software in the biological signal measurement device 1, and the output is calculated by the processing unit 11. However, it may be provided circuitously in a part of the light - receiving input unit 15 or the like. Also, it may be used as a high - pass filter instead of the band - pass filter. The determination waveform of the transmitted light intensity I used for determination may be from a predetermined time after the start of compression Ps. For example, in the waveforms shown in Figs. 2 and 3, excluding the period when the transmitted light intensity I changes greatly immediately after the start of compression Ps, a determination waveform starting 1 second after the start of compression Ps and ending at the end of compression Pr can be used. Note that when determining whether pulsation is observed during the compression period Ps - Pr, other frequency analyses may be used in addition to the above - mentioned filter. Also, image recognition of the waveform, feature recognition of the waveform (such as preset template matching), AI recognition, etc. can be used.

[0023] (2) Determination of insufficient compression based on the change amount Ic of the transmitted light intensity I of the transmitted light As shown in FIGS. 2 and 3, the change amount Ic of the transmitted light intensity in the present embodiment is obtained as the difference between the transmitted light intensity I at the start of compression Ps and the transmitted light intensity I at the end of compression Pr. And when the change amount Ic of the transmitted light intensity is smaller than the determination threshold Ith, it is determined that it is inappropriate for calculating the capillary refill time CRT. In the transmitted light intensity change in FIG. 2, since the change amount Ic of the transmitted light intensity > the determination threshold Ith, it is determined that it is appropriate for calculating the capillary refill time CRT. On the other hand, in the transmitted light intensity change in FIG. 3, since the change amount Ic of the transmitted light intensity < the determination threshold Ith, it is determined that it is inappropriate for calculating the capillary refill time CRT.

[0024] The change amount Ic of the transmitted light intensity in the present embodiment is the difference between the transmitted light intensity I at the start of compression Ps and the transmitted light intensity I at the end of compression Pr. However, the change amount Ic of the transmitted light intensity may be other quantities, such as the difference between the average value of the transmitted light intensity I of the baseline BL in the predetermined period tf before the start, which is the period immediately before the start of compression Ps, and the transmitted light intensity I at the end of compression Pr. For example, the change amount Ic of the transmitted light intensity may be the difference between a predetermined value Ir for calculating the aforementioned capillary refill time CRT and the transmitted light intensity I at the end of compression Pr. Also, it may be the difference between the average value of the transmitted light intensity I in a predetermined period after the change amount of the transmitted light intensity I becomes less than or equal to a certain value after the end of compression Pr and the transmitted light intensity I at the end of compression Pr.

[0025] Regarding how to set the determination threshold Ith, the following two examples can be given. (2a) Setting the determination threshold Ith as a fixed value The determination threshold Ith is set as a preset fixed value. The determination threshold Ith is stored in the storage unit 12 of the biological signal measuring device 1 as a fixed value.

[0026] (2b) Calculating the determination threshold Ith based on the waveform (baseline BL) before the start of compression Ps Using at least one of the pulsation rate P, transmitted light intensity I, and light emission unit light emission intensity L of the waveform (baseline BL) before Ps at the start of compression, the calculated value is set as the determination threshold Ith. In FIGS. 2 and 3, the waveform of the pre-specified period tf (about 2.5 seconds) immediately before the start of compression Ps is used as the baseline BL. For the calculation, data of the baseline BL of the transmitted light intensity I measured by a large number of subjects is used.

[0027] (2b1) Determination of the determination threshold Ith by a function obtained from data of the pulsation rate P before compression and the change amount Ic of the transmitted light intensity due to compression FIG. 4 is a plot with the pulsation rate P before compression on the horizontal axis and the change amount Ic of the transmitted light intensity due to compression on the vertical axis, based on data of the change in the transmitted light intensity I measured by a large number of subjects. In the present embodiment, the pulsation rate P is obtained by (maximum value - minimum value) / average value of the transmitted light intensity I in the pre-specified period tf before the start.

[0028] Each point in FIG. 4 is distributed from the lower left to the upper right as a whole, and it can be seen that the pulsation rate P and the change amount Ic of the transmitted light intensity of the baseline BL in the pre-specified period tf before the start have a certain correlation. This correlation is considered to be due to the fact that when the blood volume in the measurement unit is large, the pulsation rate P is large, and since the blood volume excluded by compression is also large, the change amount Ic of the transmitted light intensity also becomes large. (A1) is the regression line of this data. And using the regression line (A1) which is a linear function, the determination threshold Ith can be obtained from the pulsation rate P before compression. For example, as shown in FIG. 4, when the pulsation rate P is Px, Ith1 which is the value of the Y axis of the regression line (A1) corresponding to Px is set as the determination threshold Ith.

[0029] Also, (B1) is a lower limit line showing the lower limit of the distribution of each point. And using the lower limit line (B1) which is a linear function, the determination threshold Ith can be obtained from the pulsation rate P before compression. For example, as shown in FIG. 4, when the pulsation rate P is Px, Ith2 which is the value of the Y axis of the lower limit line (B1) corresponding to Px is set as the determination threshold Ith. Note that the lower limit may be not only a straight line which is a linear function but also a function of a broken line or a curve.

[0030] (2b2) Determination of the determination threshold Ith by the function obtained from the values of the regression equation obtained by multiple regression analysis and the data of the transmitted light intensity change amount Ic As can be seen from the fact that the transmitted light intensity change amount Ic and the pulsation rate P before compression in FIG. 4 are distributed from the lower left to the upper right, they have a certain degree of correlation. However, it is more desirable to determine the determination threshold Ith using an index with a greater correlation. Therefore, from the data of the transmitted light intensity changes measured in a large number of subjects, multiple regression analysis is performed with the "transmitted light intensity change amount Ic due to compression" as the objective variable and the "pulsation rate P before compression, transmitted light intensity I, light emission intensity L of the light emitting part", etc. as explanatory variables, and the determination threshold Ith may be calculated from the regression equation at that time.

[0031] For example, since the transmitted light intensity I changes when the thickness of the finger F is different, the pulsation rate P before compression may also change depending on the thickness of the finger F. Therefore, it is conceivable to use the pulsation rate P before compression and the transmitted light intensity DC value Id, which is the DC component of the transmitted light intensity I before compression, as explanatory variables and the transmitted light intensity change amount Ic as the objective variable. In that case, it becomes as follows. The transmitted light intensity change amount Ic is set as a linear function of the pulsation rate P and the transmitted light intensity DC value Id. Transmitted light intensity change amount Ic = a * pulsation rate P + b * transmitted light intensity DC value Id + c ··· Equation [1] a, b, and c are constants. Then, multiple regression analysis is performed with the transmitted light intensity change amount Ic as the objective variable and the pulsation rate P and the transmitted light intensity DC value Id as explanatory variables to determine the constants a, b, and c.

[0032] Then, when the pulsation rate P and the transmitted light intensity DC value Id are determined, the estimated value Ce of the transmitted light intensity change amount Ic by the regression equation can be calculated. FIG. 5 shows the estimated value Ce calculated as follows with the horizontal axis after performing multiple regression analysis and determining the constants a, b, and c. The vertical axis is the measured value Ca of the transmitted light intensity change amount Ic due to compression. Estimated value Ce = a * pulsation rate P + b * transmitted light intensity DC value Id + c ··· Equation [2] Note that, similar to the example of FIG. 4, the pulsation rate P is (maximum value - minimum value) / average value of the transmitted light intensity I in the predetermined period tf before the start.

[0033] FIG. 5 shows data of the transmitted light intensity change, which is the change in the transmitted light intensity I measured in a number of subjects, and plots the estimated value Ce calculated by Equation [2] and the change amount Ic of the transmitted light intensity due to compression. In FIG. 5, the distribution from the lower left to the upper right is stronger than in FIG. 4, and it can be seen that the correlation is larger.

[0034] (A2) is the regression line obtained from each point in FIG. 5. Then, using the regression line (A2) which is a linear function, the determination threshold Ith can be obtained from the estimated value Ce. For example, as shown in FIG. 5, when the estimated value Ce is Cex, Ith3 which is the value of the Y-axis of the regression line (A2) corresponding to Cex is set as the determination threshold Ith.

[0035] Also, (B2) is the lower limit line showing the lower limit of the distribution of each point. Then, using the lower limit line (B2) which is a linear function, the determination threshold Ith can be obtained from the estimated value Ce. For example, as shown in FIG. 5, when the estimated value Ce is Cex, Ith4 which is the value of the Y-axis of the lower limit line (B2) corresponding to Cex is set as the determination threshold Ith. Note that the lower limit may be not only a straight line which is a linear function but also a broken line or a curve function.

[0036] In the present embodiment, when it is detected that the states (1) or (2) above are present and it is determined that the compression is insufficient, remeasurement is automatically performed by increasing the compression target value to compress the biological tissue, or by increasing the compression time to compress the biological tissue. Further, notification may be given to prompt remeasurement by increasing the compression target value or to prompt remeasurement by increasing the compression time. This notification can also be used when compression is performed manually. When it is determined that the compression is still insufficient even after performing these remeasurements, a non-measurable notification may be given. Further, when the states (1) or (2) are detected, a simple notification that the capillary refill time CRT is non-measurable may be given. In the present embodiment, the notification is given when information corresponding to the notification is sent from the result output unit 17 and is notified from a voice generator, a display device, etc. (not shown).

[0037] In the embodiment, in FIGS. 4 and 5, data on changes in the transmitted light intensity I measured in a large number of subjects were used. However, a plurality of data on changes in the transmitted light intensity I measured in one subject may be used. Data on changes in the transmitted light intensity measured in at least one subject can be used.

[0038] <When there is a positional shift between the light emitting unit 211 and the light receiving unit 213, or a shift in the compression direction> As described above, not only when the compression of the finger F, which is a biological tissue, is insufficient, but also when the positional relationship between the light emitting unit 211 and the light receiving unit 213 attached to the finger F or the compression direction to the finger F is inappropriate, it is inappropriate for calculating the capillary refill time CRT. If the change in the transmitted light intensity I has any of the following two characteristics, there may be a possibility that the positional relationship between the light emitting unit 211 and the light receiving unit 213 or the compression direction to the finger F is inappropriate. (3) When a protrusion shape occurs at least immediately after the start of compression Ps or immediately after the release of compression Pr. (4) When a decrease in the transmitted light intensity I from the baseline BL before the compression section occurs.

[0039] Specific examples of the case where the positional relationship and compression direction between the light emitting unit 211 and the light receiving unit 213 are not aligned are shown below. FIGS. 6 and 7 are Example 1 and Example 2 showing a mounted state in which the positional relationship between the light emitting unit 211 and the light receiving unit 213 is shifted. The pressure from the bag film 222 attached to the lid 221 of the support tool 22 compresses the finger F from above as a downward compression Pd. Further, since the finger F is held by the support 224, the finger F is compressed from below as an upward compression Pu from the support 224. FIG. 6 is a side view of the finger F. In the mounted state of FIG. 6, the light receiving unit 213 is attached to the tip side of the finger F rather than the finger pad B. Therefore, the emission optical axis 211A, which is the optical axis of the light emitting unit 211 installed on the nail N, and the light receiving optical axis 213A, which is the optical axis of the light receiving unit 213, are shifted and intersect at an angle equal to or greater than a predetermined angle. In Example 1 of FIG. 6, the directions of the upward compression Pu and the downward compression Pd are substantially the same.

[0040] FIG. 7 is a view of the mounted state of the light emitting unit 211 and the light receiving unit 213 in Example 2, which is another example from FIG. 6, as viewed from the fingertip side of the finger F. In the mounted state of FIG. 7, the light receiving unit 213 is attached to the side surface side of the finger F rather than the finger pad B. Therefore, the emission optical axis 211A, which is the optical axis of the light emitting unit 211 installed on the nail N, and the light receiving optical axis 213A, which is the optical axis of the light receiving unit 213, are shifted and intersect at an angle equal to or greater than a predetermined angle. Also in the mounted state of Example 2 shown in FIG. 7, the directions of the upward compression Pu and the downward compression Pd are substantially the same. Although not shown in the drawings, when the light receiving unit 213 is located on the diagonal side of the tip side of the finger F or when the emission optical axis 211A and the light receiving optical axis 213A are in a twisted position, the positional relationship between the light emitting unit 211 and the light receiving unit 213 is inappropriate in the same way.

[0041] When the emission optical axis 211A and the light receiving optical axis 213A intersect at an angle equal to or greater than a predetermined angle or are in a twisted position as in the mounted states of Example 1 and Example 2 shown in FIGS. 6 and 7, the light emitted from the light emitting unit 211 hardly enters the light receiving unit 213, which is inappropriate for calculating the capillary refill time CRT. Such mounted states of the light emitting unit 211 and the light receiving unit 213 occur when, for example, the fixing of the light emitting unit 211 and the light receiving unit 213 to the finger F by a tape (not shown) is inappropriate.

[0042] Also, Fig. 8 shows an example where the directions of the upward compression Pu and the downward compression Pd are misaligned. In this mounted state, the emission optical axis 211A, which is the optical axis of the light-emitting unit 211 installed on the claw N, and the reception optical axis 213A, which is the optical axis of the light-receiving unit 213, are not misaligned and are coincident. However, when the finger F is compressed in such a compression state, due to the upward compression Pu and the downward compression Pd with misaligned directions, the positions of the light-emitting unit 211 and the light-receiving unit 213 are laterally misaligned, and the emission optical axis 211A and the reception optical axis 213A are misaligned. Therefore, the light emitted from the light-emitting unit 211 becomes difficult to enter the light-receiving unit 213, making it inappropriate for calculating the capillary refill time CRT. A misalignment in the compression direction occurs as shown in Fig. 8 when the attachment method of the assisting tool 22 to the finger F is defective or when the sizes of the finger F and the assisting tool 22 are not suitable.

[0043] In a mounted state where the positional relationship between the light-emitting unit 211 and the light-receiving unit 213 is misaligned as in Examples 1 and 2 of Figs. 6 and 7, or in a compression state where the directions of the upward compression Pu and the downward compression Pd are misaligned as in Fig. 8, a special-shaped waveform occurs. The same applies to a mounted state where misalignments occur in both the positional relationship between the light-emitting unit 211 and the light-receiving unit 213 and the directions of the upward compression Pu and the downward compression Pd. By capturing this waveform, it is possible to determine whether it is appropriate for calculating the capillary refill time CRT. The graphs of the change in the transmitted light intensity I shown in Figs. 9 and 10 as Examples 1 and 2 indicate that such misalignments have occurred.

[0044] The transmitted light intensity I in Fig. 9 of Example 1 increases immediately after the start of compression Ps, but decreases slightly after a certain period of time, and shows a change of once increasing immediately after the release of compression Pr and then greatly decreasing. As described above, when the finger F is compressed, the blood in the biological tissue is excluded, and the light absorption by the blood decreases, so the transmitted light intensity I increases. However, immediately after that, when the positional relationship between the light emitting part 211 and the light receiving part 213 is shifted due to compression, the angle of the light receiving optical axis 213A shown in Figs. 6 and 7 changes, and the angle between the light emitting optical axis 211A and the light receiving optical axis 213A shifts in a direction approaching 90°. As in the wearing states of Examples 1 and 2 shown in Figs. 6 and 7, if the positional relationship between the light emitting part 211 and the light receiving part 213 is shifted before compression, the shift is enlarged by compression, and the transmitted light reaching the light receiving part 213 decreases. Further, even if the positional relationship between the light emitting part 211 and the light receiving part 213 is not shifted, if the directions of upward compression Pu and downward compression Pd are shifted as shown in Fig. 8, the positional relationship between the light emitting part 211 and the light receiving part 213 is shifted by compression. Thereby, the light emitting optical axis 211A and the light receiving optical axis 213A are also shifted, and the transmitted light reaching the light receiving part 213 decreases. Due to the influence of these transmitted light decreases, which is contrary to the increase in transmitted light intensity I accompanying the decrease in blood during compression, the protrusion shape during the compression period Ps - Pr as shown in the figure occurs.

[0045] When the influence of light reduction becomes even greater, the received light intensity during the compression period Ps - Pr becomes smaller than the received light intensity before the compression period Ps - Pr, and it becomes as shown in Fig. 10 as Example 2. In Fig. 10, the transmitted light intensity I has been lower than the baseline BL before the start of compression Ps immediately after the start of compression Ps.

[0046] Specifically, in the following cases shown in Fig. 9, it is determined as a positional shift or a compression direction shift of the sensor. (3) Presence or absence of a protrusion shape immediately after the start of compression Ps and immediately after the release of compression Pr The processing unit 11, which is an information processing unit, determines that it is inappropriate if a peak of the transmitted light intensity I exists in at least one of the predetermined periods ts after the start, which is a predetermined period immediately after the start Ps of compression, and the predetermined period tr after the release, which is a predetermined period immediately after the release Pr of compression, in the fluctuation of the received light intensity. The presence of peaks immediately after the start Ps of compression and immediately after the release Pr of compression can be detected from the time change of the differential value of the transmitted light intensity I in the predetermined period ts after the start and the predetermined period tr after the release. It can also be detected by other methods, such as whether a maximum value exists in the predetermined period ts after the start or the predetermined period tr after the release.

[0047] Furthermore, the processing unit 11, which is an information processing unit, may be configured to determine that it is inappropriate when a peak of the transmitted light intensity I exists on one side immediately after the start Ps of compression and immediately after the release Pr of compression in the change of the received light intensity, and the transmitted light intensity I in the vicinity of the peak of the transmitted light intensity I (within a predetermined range from the value of the peak) exists on the other side.

[0048] Specifically, it is also possible to determine sensor misalignment or compression direction misalignment in the following cases shown in FIG. 10. (4) Decrease in the transmitted light intensity I from the baseline BL before the compression section In FIG. 10, the waveform in the predetermined period tf (about 2.5 seconds) before the start, immediately before the start Ps of compression, is used as the baseline BL. When the value of the transmitted light intensity Ip during compression, which is the transmitted light intensity I at 1 second after the start Ps of compression, is smaller than the average transmitted light intensity Iv before compression, which is the average of the transmitted light intensity I on the baseline BL, it is determined that there is sensor misalignment or compression direction misalignment.

[0049] Regarding the change in the transmitted light intensity with the shape shown in FIG. 10, when the average value of the transmitted light intensity I in the predetermined period tr after the release Pr of compression is larger than the transmitted light intensity Ib at the release Pr of compression, which is the transmitted light intensity I at the release Pr of compression, it can also be determined that there is sensor misalignment or compression direction misalignment. It can also be determined by other methods, such as detecting from the time change of the differential value of the transmitted light intensity I immediately after the start Ps of compression and immediately after the release Pr of compression.

[0050] In this embodiment, when the states (3) and (4) above are detected and it is determined that it is inappropriate for calculating the capillary refill time CRT, the position-direction inappropriate information is sent from the result output unit 17, and notifications are given from a voice generator and a display device (not shown) and the like that the positional relationship and the compression direction between the light emitting unit 211 and the light receiving unit 213 are inappropriate. Further, notifications may be given to prompt correction of the position of the sensor and the compression direction. Both notifications indicating inappropriateness and notifications prompting correction may be given, or either one may be given. The user who has received such a notification can reattach the light emitting unit 211 and the light receiving unit 213 to the finger F or reattach the support tool 22 to the finger F so that the capillary refill time CRT can be calculated. This notification can also be used when performing compression manually. The user who has received the notification can reattach the light emitting unit 211 and the light receiving unit 213 to the finger F or pay attention to the compression direction and perform compression so that the capillary refill time CRT can be calculated. Further, when the states (3) and (4) are detected, a notification that the capillary refill time CRT cannot be measured may simply be given.

[0051] In the embodiment, the start pressure Ps and the release pressure Pr at the start of compression can be determined based on the control from the processing unit 11 to the pressure generating unit 13 in the biological signal measuring device 1. However, the start pressure Ps and the release pressure Pr at the start of compression may be detected from the waveform of the transmitted light intensity I.

[0052] In the embodiment, the compression period Ps - Pr is automatically formed, but the user may manually form a compression state that becomes the compression period Ps - Pr by pressing the finger F of the subject or the like. In that case, the start pressure Ps and the release pressure Pr at the start of compression can be detected from the waveform of the transmitted light intensity I.

[0053] In the embodiment, circulatory disorder information, positional and directional inappropriateness information, etc. are sent from the result output unit 17 and notified by a voice generator, a display device, etc. However, a notification unit such as a voice generator and a display device may be provided in the biological signal measurement device 1 so as to perform notification from the notification unit. The biological signal measurement device may use one of various determinations indicating that it is inappropriate for calculating the above-described capillary refill time CRT, or may use a combination of a plurality of them.

[0054] The processing unit 11 of the biological signal measurement device 1 in the above embodiment is a computer, and based on the fluctuation of the received light intensity received by the light receiving unit 213 that receives the light irradiated from the light emitting unit 211 and transmitted through the biological tissue, a capillary refill time calculation procedure for calculating the capillary refill time CRT after the compression period Ps - Pr during which the biological tissue is compressed, and a calculation validity determination procedure for determining whether or not the fluctuation of the received light intensity is appropriate for calculating the capillary refill time CRT using the received light intensity are performed.

[0055] Further, the processing unit 11 of the biological signal measurement device 1 is a computer, and based on the fluctuation of the received light intensity received by the light receiving unit 213 that receives the light irradiated from the light emitting unit 211 and transmitted through the biological tissue by a biological signal measurement program, a capillary refill time calculation function for calculating the capillary refill time CRT after the compression period Ps - Pr during which the biological tissue is compressed, and a calculation validity determination function for determining whether or not the fluctuation of the received light intensity is appropriate for calculating the capillary refill time CRT using the received light intensity are realized.

[0056] Furthermore, a biological signal measurement program for causing a computer to implement a capillary refill time calculation procedure for calculating a capillary refill time CRT after a compression period Ps-Pr during which the biological tissue is compressed, based on fluctuations in the received light intensity received by a light receiving unit 213 that receives light irradiated from a light emitting unit 211 and transmitted through the biological tissue, and a calculation validity determination procedure for determining whether or not fluctuations in the received light intensity are appropriate for calculating the capillary refill time CRT using the received light intensity, can be recorded on a computer-readable recording medium. This recording medium includes both temporary and non-temporary ones.

[0057] As described above, the embodiments of the present invention have been described in detail. However, the specific configuration is not limited to these embodiments, and design changes and the like within the scope not departing from the gist of the present invention are also included in the present invention. As long as there are no particular contradictions or problems in their purposes and configurations, etc., the above-described embodiments can be combined by diverting each other's technologies.

Explanation of Reference Numerals

[0058] Finger F Nail N Finger Pad B Transmitted Light Intensity I Transmitted Light Intensity at Release Ib Transmitted Light Intensity during Compression Ip Average Transmitted Light before Compression Iv Change Amount of Transmitted Light Intensity Ic DC Value of Transmitted Light Intensity Id Predetermined Value Ir Start of Compression Ps Release of Compression Pr Compression Period Ps-Pr Capillary Refill Time CRT Predetermined Period before Start tf Estimated Value Ce Measured Value Ca Pulse Rate P Pulse Rate Px Light Emitting Intensity of Light Emitting Unit L Upward Compression Pu Downward Compression Pd Baseline BL Ith determination threshold value Ith1 determination threshold value Ith2 determination threshold value Ith3 determination threshold value Ith4 determination threshold value Predetermined period after the start of ts Predetermined period after the release of tr 1 Biological signal measurement device 11 Processing unit 12 Memory unit 13 Pressure generation unit 14 Light emission output unit 15 Light reception input unit 16 Switch input unit 161 Inspection switch 17 Result output unit 2 Biological signal acquirer 21 Sensor instrument 211 Light emission unit 211A Light emission optical axis 212 Wiring 213 Light reception unit 213A Light reception optical axis 214 Wiring 22 Support tool 221 Cover 221a Pressure chamber 222 Bag film 223 Tube 224 Support body 225 Hinge part

Claims

1. An information processing unit that calculates the capillary refill time after a compression period during which the biological tissue is compressed based on fluctuations in the received light intensity received by a light receiving unit that receives light irradiated from a light emitting unit and transmitted through the biological tissue. The information processing unit is characterized in that it uses the received light intensity to determine whether the fluctuation of the received light intensity is appropriate for calculating the capillary refill time. A biological signal measuring device.

2. The information processing unit according to claim 1, wherein when a pulsation is detected in the received light intensity during the compression period, it is determined that it is not appropriate for calculating the capillary refill time.

3. The information processing unit according to claim 1, wherein when the amount of change in the transmitted light intensity, which is the amount of change in the transmitted light intensity due to compression, is smaller than a determination threshold value, it is determined that it is not appropriate for calculating the capillary refill time.

4. The biological signal measuring device according to claim 3, wherein the determination threshold value is a preset fixed value.

5. The determination threshold value is a value calculated using at least one of the received light intensity before the compression period or the pulsation rate calculated from the fluctuation of the received light intensity before the compression period. The biological signal measuring device according to claim 3.

6. The biological signal measuring device according to claim 5, wherein the determination threshold value is calculated based on the distribution of data on the change in transmitted light intensity measured in at least one subject.

7. The biological signal measuring device according to claim 6, wherein the determination threshold value is calculated by a regression line or a lower limit in the distribution of data on the change in transmitted light intensity measured in at least one subject.

8. The information processing unit according to claim 1, wherein when there is a peak in the transmitted light intensity at at least one of immediately after the start of compression and immediately after the release of compression in the fluctuation of the received light intensity, it is determined that it is not appropriate.

9. The information processing unit according to claim 1, wherein when there is a peak in the transmitted light intensity at one of immediately after the start of compression and immediately after the release of compression in the fluctuation of the received light intensity, and there is a transmitted light intensity within a predetermined range from the value of the peak at the other, it is determined that it is not appropriate.

10. The biological signal measuring device according to claim 1, wherein the information processing unit determines that it is inappropriate when the received light intensity during the compression period is smaller than the received light intensity before the compression period.

11. When the information processing unit determines that it is inappropriate, it is provided with a notification unit that performs at least one of a notification of the possibility of insufficient compression, a notification prompting remeasurement by increasing the pressurization target value, and a notification prompting remeasurement by increasing the compression time. The biological signal measuring device according to any one of claims 1 to 7.

12. The biological signal measuring device according to any one of claims 1 to 7, wherein the compression period is formed by automatically compressing with an automatic compression device.

13. When the information processing unit determines that it is inappropriate, it automatically performs remeasurement by compressing the biological tissue by increasing at least one of the pressurization target value and the compression time. The biological signal measuring device according to any one of claims 1 to 7.

14. When the information processing unit determines that it is inappropriate, it includes a notification unit that performs at least one of a notification of the possibility that at least one of the positional relationship between the light emitting unit and the light receiving unit or the direction of compression is inappropriate, and a notification prompting correction of the position of the light emitting unit or the light receiving unit or the direction of compression. The biological signal measuring device according to any one of claims 8 to 10.

15. A biological signal acquirer having a support tool for applying pressure to or releasing pressure from the biological tissue, The biological signal measuring device according to any one of claims 1 to 10, A biological signal measuring system characterized by comprising:

16. A capillary refill time calculation procedure for calculating a capillary refill time after a compression period during which the biological tissue is compressed based on fluctuations in the received light intensity received by a light receiving unit that receives light transmitted through the biological tissue after being irradiated from a light emitting unit, A calculation validity determination procedure for determining whether fluctuations in the received light intensity are appropriate for calculating the capillary refill time using the received light intensity, A biological signal measuring method characterized by comprising:

17. On a computer, A capillary refill time calculation function for calculating a capillary refill time after a compression period during which the biological tissue is compressed based on fluctuations in the received light intensity received by a light receiving unit that receives light transmitted through the biological tissue after being irradiated from a light emitting unit, A calculation validity determination function that uses the received light intensity to determine whether the fluctuation of the received light intensity is appropriate for calculating the capillary refill time, A biological signal measurement program for realizing the above.

18. On a computer, Based on the fluctuation of the received light intensity received by a light receiving unit that receives light irradiated from a light emitting unit and transmitted through biological tissue, a capillary refill time calculation procedure for calculating the capillary refill time after the compression period during which the biological tissue is compressed, A calculation validity determination procedure that uses the received light intensity to determine whether the fluctuation of the received light intensity is appropriate for calculating the capillary refill time, A computer-readable recording medium on which a biological signal measurement program for realizing the above is recorded.

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