Blood flow meter

Abstract

Provided is a blood flow meter that can easily be adjusted to a predetermined surface temperature and a predetermined pressing pressure for a measurement region. A blood flow meter 1 comprises a measurement probe 10 which has an irradiation part 111 for radiating laser light, a light-receiving part 112 for receiving reflected light and scattered light, a pressure sensor 113 for measuring a pressing pressure, and a temperature sensor 114 for measuring the temperature of a tissue surface. The blood flow meter 1 preferably further comprises a reporting unit 23 for reporting whether measurement of a blood flow rate is possible, and a control unit 24 for causing the reporting unit 23 to operate so as to report that measurement of a blood flow rate is possible when the pressing pressure measured by the pressure sensor 113 is in a predetermined pressure range and the temperature of the tissue surface measured by the temperature sensor 114 is in a predetermined temperature range.

Description

[Technical field]

[0001] The present invention relates to a blood flow meter that measures blood flow rate by bringing a measuring probe into contact with a tissue surface, and a measuring probe used in the blood flow meter. [Background technology]

[0002] Laser blood flow meters are known as blood flow meters that measure blood flow on the tissue surface of the skin, digestive tract mucosa, etc. Laser blood flow meters are devices that non-invasively and continuously measure microcirculatory blood flow (tissue blood flow) in capillaries and arterioles several mm beneath the skin, and were developed for the purpose of confirming the presence or absence of disease and the effectiveness of treatment. A blood flow meter basically consists of a main body with a display unit that displays blood flow rate and an operation unit, and a measurement probe with a laser light emitting unit and a light receiving unit.The measurement principle is that the measurement probe is placed in close contact with the measurement site, such as the skin surface or the digestive tract mucosa surface, and near-infrared light is emitted from a semiconductor laser.The reflected light from the tissue surface and scattered light from moving red blood cells are received by a light receiving element and converted into an electrical signal, and the blood flow rate is measured using an arithmetic formula.

[0003] When measuring blood flow with a laser blood flow meter, the measurement probe is placed in close contact with the tissue surface, but if the pressure of the measurement probe against the skin surface is too strong, the blood flow is obstructed and the blood flow cannot be measured correctly. Therefore, Patent Documents 1 and 2 propose reducing the variation in the measurement value by providing a pressure sensor on the measurement probe and measuring the blood flow at a pressure equal to or lower than a standard pressure. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 63-97146 [Patent Document 2] Publication No. 3-21208 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, in clinical practice, laser blood flow meters are used to confirm the effect of continuous treatment for each patient. When measuring blood flow using a laser blood flow meter, the measured value of blood flow varies depending on the measurement conditions, so it is required to measure blood flow under constant measurement conditions for each patient. Here, the measurement conditions include the measurement site, body position, rest, environmental temperature, pressure applied to the measurement site, surface temperature of the measurement site, etc. Among these measurement conditions, the measurement site, body position, rest, and environmental temperature can be easily made constant under predetermined conditions for each patient. In order to standardize the measurement conditions for each patient, as proposed in the above-mentioned Patent Documents 1 and 2, a pressure sensor is provided on the measurement probe, and the pressing pressure during measurement can be adjusted to a predetermined value, thereby reducing the variation in blood flow caused by the fluctuation of the pressing pressure. However, if the surface temperature of the measurement site differs from measurement to measurement, even if the pressing pressure is adjusted to a predetermined value, the blood flow will vary due to the fluctuation of the surface temperature. Therefore, unless the surface temperature of the measurement site is also adjusted to a predetermined value in addition to the pressing pressure, the blood flow cannot be evaluated correctly, and it becomes difficult to confirm the effect of the treatment.

[0006] SUMMARY OF THE PRESENT DISCLOSURE OF THE PRESENT DISCLOSURE It is therefore an object of the present invention to provide a blood flow meter and a measurement probe for use with said blood flow meter, which are easily adjustable to a predetermined pressing pressure and a predetermined surface temperature for a measurement site. [Means for solving the problem]

[0007] The present invention relates to a blood flow meter equipped with a measurement probe that is brought into contact with a tissue surface to measure blood flow, the measurement probe having an irradiation unit that irradiates laser light toward the tissue surface, a light receiving unit that receives reflected light and scattered light from the tissue surface, a pressure sensor that measures the pressing pressure against the tissue surface, and a temperature sensor that measures the temperature of the tissue surface.

[0008] In addition, the blood flow meter further includes an alarm unit that notifies whether or not blood flow measurement is possible, and a control unit that activates the alarm unit, and it is preferable that the control unit activates the alarm unit when the pressing pressure measured by the pressure sensor falls within a predetermined pressure range and the temperature of the tissue surface measured by the temperature sensor falls within a predetermined temperature range.

[0009] In addition, it is preferable that the notification unit includes a pressure notification unit that notifies whether the pressing pressure measured by the pressure sensor is within a predetermined pressure range, and a temperature notification unit that notifies whether the temperature of the tissue surface measured by the temperature sensor is within a predetermined temperature range.

[0010] In addition, it is preferable that the control unit starts measuring blood flow by controlling the irradiation unit to irradiate laser light after a certain time has elapsed after the pressing pressure measured by the pressure sensor falls within a predetermined pressure range and the temperature of the tissue surface measured by the temperature sensor falls within a predetermined temperature range.

[0011] It is also preferable that the predetermined pressure range can be set to any value within the range of 0.3N to 1.5N.

[0012] It is also preferable that the predetermined pressure range can be set to any value within the range of 0.8N to 1.2N.

[0013] It is also preferable that the predetermined temperature range can be set to any value within the range of 10°C or more and 40°C or less.

[0014] The present invention also relates to a measurement probe used in a blood flow meter that measures blood flow by contacting the surface of tissue, the measurement probe having an irradiation unit that irradiates laser light toward the tissue surface, a light receiving unit that receives reflected light and scattered light from the tissue surface, a pressure sensor that measures the pressure applied to the tissue surface, and a temperature sensor that measures the temperature of the tissue surface.

[0015] In addition, it is preferable that the measurement probe further includes an alarm unit that notifies whether or not blood flow measurement is possible, and a control unit that activates the alarm unit, and that the control unit activates the alarm unit when the pressing pressure measured by the pressure sensor falls within a predetermined pressure range and the temperature of the tissue surface measured by the temperature sensor falls within a predetermined temperature range. Effect of the Invention

[0016] According to the blood flow meter and measuring probe of the present invention, it is possible to measure the pressing pressure and temperature of the skin surface (tissue surface) as the measurement site, and the blood flow rate can be measured with stable accuracy. [Brief description of the drawings]

[0017] [Figure 1] 1 is a diagram showing the appearance of a blood flow meter according to a first embodiment of the present invention; [Diagram 2] FIG. 1 is a block diagram showing a configuration of a blood flow meter according to the present invention. [Diagram 3] These are the results of measuring blood flow in the arm or leg by changing the pressure with which the measurement probe was pressed against the skin surface. [Figure 4] Based on the results measured in FIG. 3, this shows the rate of change in blood flow when the pressure of the measurement probe against the skin surface is changed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Each embodiment of the present invention will be described in detail below with reference to Figures 1 and 2. In this embodiment, a case will be described in which blood flow is measured on the skin surface as an example of a tissue surface at a measurement site.

[0019] FIG. 1 is a diagram showing the appearance of a blood flow meter 1 of the first embodiment. The blood flow meter 1 includes a measurement probe 10 and a main body section 20.

[0020] As shown in Fig. 2, the measurement probe 10 (head 11) includes the head 11 having an irradiating section 111, a light receiving section 112, a pressure sensor 113, and a temperature sensor 114, and a cable 12 connected to the main body section 20 (see Fig. 1). The head 11 has an opening 110 for irradiating and receiving laser light, in which the irradiating section 111 that irradiates laser light and the light receiving section 112 that receives reflected light and scattered light of the laser light from the skin surface are disposed. The irradiation unit 111 is configured with a light emitting unit that is configured with a semiconductor laser that emits near-infrared light. The light emitting unit may be provided in the main body 20, and an optical fiber may be passed through the cable 12 to introduce the near-infrared light into the opening 110. The light receiving unit 112 is composed of a photodiode that converts light into an electrical signal. In the light receiving unit 112, the near-infrared light irradiated from the irradiating unit 111, reflected from the skin surface (tissue surface), and the light scattered by red blood cells are converted into electrical signals. Based on the converted electrical signals, the blood flow rate is calculated by the control unit 24, which will be described later, using the principle of the Doppler method. Further, a pressure sensor 113 and a temperature sensor 114 are disposed near the opening 110 of the head 11. Existing thin-film sensors can be used as the pressure sensor 113 and the temperature sensor 114. Further, the head 11 may be configured to include a heater as a heating mechanism to adjust the temperature of the skin surface (tissue surface).

[0021] As shown in FIG. 2, the main body 20 includes an operation unit 21, a display unit 22, a notification unit 23, and a control unit 24. The main body 20 is configured to be connectable to a terminal such as a personal computer or a tablet by wire or wirelessly, and various settings such as a predetermined pressure range for the pressing pressure and a predetermined temperature range for the skin surface (tissue surface) can be made using designated application software. Also, the main body 20 may be provided with an operation unit such as a setting button to make various settings.

[0022] The operation unit 21 includes a power button 211, a measurement start / stop button 212, and the like.

[0023] The display unit 22 is composed of a liquid crystal screen or the like capable of displaying the measured pressure on the skin surface, the measured temperature of the skin surface, etc. By displaying the pressure on the display unit 22, it becomes possible to attach the measurement probe 10 to the measurement site while adjusting the pressure so that it becomes a predetermined pressure.

[0024] The notification unit 23 notifies whether or not the blood flow rate can be measured. In this embodiment, the notification unit 23 is composed of a light-emitting diode as the pressure notification unit 231 that lights up to notify when the pressing pressure falls within a predetermined pressure range, and a light-emitting diode as the temperature notification unit 232 that lights up to notify when the temperature of the skin surface (tissue surface) falls within a predetermined temperature range. By lighting up the two light-emitting diodes as the pressure notification unit 231 and the temperature notification unit 232, it is possible to know that the blood flow meter 1 is in a state where the blood flow rate can be measured with high accuracy. Alternatively, a configuration may be adopted in which only one light-emitting diode is provided that lights up to notify that the measurement can be started when both the pressing pressure and the temperature of the skin surface (tissue surface) fall within the predetermined range. Alternatively, the notification unit 23 may be configured to display on the display unit 22 whether or not the blood flow rate can be measured, and to notify the user.

[0025] The control unit 24 is composed of a CPU (Central Processing Unit) that controls the entire blood flow meter 1, and is connected to each component of the head 11 via the cable 12, and controls the operations of the operation unit 21, display unit 22, and notification unit 23 of the main body 20. The control unit 24 also calculates and measures the blood flow rate, pressing pressure, temperature of the skin surface (tissue surface), etc. from electrical signals converted by various sensors such as the light receiving unit 112, pressure sensor 113, and temperature sensor 114, and displays the information on the display unit 22. If the head 11 of the measurement probe 10 is equipped with a heating mechanism, the control unit 24 controls the temperature of the heating mechanism to be a preset arbitrary value or a fixed value.

[0026] Specifically, the control unit 24 controls the light-emitting diode 231 of the notification unit 23 to light up when the pressing pressure measured by the pressure sensor 113 falls within a predetermined pressure range. The control unit 24 also controls the light-emitting diode 232 of the notification unit 23 to light up when the temperature of the skin surface (tissue surface) measured by the temperature sensor 114 falls within a predetermined temperature range. This allows the operator of the blood flow meter 1 to visually check whether the pressing pressure and the temperature of the skin surface are in an appropriate state and blood flow measurement can be started, and presses the measurement start / stop button 212 to start blood flow measurement with stable accuracy. The control unit 24 may also control the blood flow measurement to automatically start without waiting for the operator to start measurement after the pressing pressure and the temperature of the skin surface (tissue surface) have become appropriate and a certain time has elapsed in that state. The control unit 24 may also be provided with a storage unit that stores data on the blood flow rate, pressing pressure, and temperature of the skin surface (tissue surface) during measurement, and configured to display the data on the display unit 22 or a terminal.

[0027] Next, a description will be given of values ​​that can be set for the predetermined pressure range of the pressing pressure and the predetermined temperature range of the skin surface (tissue surface) temperature. The pressing pressure is preferably set to any value in the range of 0.3 N to 1.5 N in order to make the blood flow rate measurable. If the pressing pressure is less than 0.3 N, the contact state between the skin surface (tissue surface) and the head 11 of the measuring probe 10 is not stable, and even slight vibrations may cause displacement. If the pressing pressure exceeds 1.5 N, there is a risk of obstructing the blood flow in the peripheral circulation. In order to further reduce the effect of changes in the pressing pressure on the blood flow rate, the pressing pressure is more preferably set to any value in the range of 0.8 N to 1.2 N inclusive. The temperature of the skin surface (tissue surface) is preferably set to any value within the range of 10°C or higher and 40°C or lower, and more preferably set to any value within the range of 15°C or higher and 40°C or lower. In this embodiment, the predetermined pressure range and the predetermined temperature range are set to arbitrary values, but fixed values ​​may be used. The predetermined temperature range may be set in relation to the room temperature of the room where the blood flow measurement is performed (where the blood flow meter is installed). In this case, the blood flow meter is configured to include a room temperature sensor that measures the room temperature. The control unit sets the predetermined temperature range based on the room temperature measured by the room temperature sensor. For example, the control unit sets a range in which the difference between the temperature measured by the room temperature sensor is equal to or less than a predetermined value as the predetermined temperature range. This allows the blood flow to be determined as being measurable when the difference between the temperature of the subject's skin surface and the room temperature is equal to or less than the predetermined value. Therefore, for example, when the subject comes from a low-temperature environment to the room where the blood flow measurement is performed, the blood flow can be measured when the subject's body has warmed up and the temperature difference between the room temperature and the skin surface has become small.

[0028] Next, we will explain the effect of skin surface temperature, which is one of the measurement conditions, on blood flow volume with reference to Table 1. Table 1 shows the results of measuring blood flow volume at the same site on the second toes on both the left and right feet when the skin surface temperature was changed.

[0029] [Table 1]

[0030] According to Table 1, it can be seen that if the skin surface temperature is different, the blood flow rate will vary significantly even at the same measurement site. This shows that it is important to evaluate the blood flow rate by keeping the skin surface temperature, which is one of the measurement conditions, constant. It can also be seen that the skin surface temperature is lower when the room temperature is low and higher when the room temperature is high. Therefore, in order to keep the measurement conditions constant, it is preferable to keep the room temperature constant.

[0031] Next, the influence of the pressure of the measurement probe on the skin surface, which is one of the measurement conditions, on the blood flow rate will be described with reference to Figures 3 and 4. Figure 3 shows the results of measuring the blood flow rate on an arm or a leg by changing the pressure of the measurement probe on the skin surface. Figure 4 shows the rate of change of the blood flow rate when the pressure of the measurement probe on the skin surface is changed based on the results measured in Figure 3.

[0032] In Figure 3, blood flow was measured for five subjects with the measurement probe pressed against the skin surface at pressures of 0.4 N, 0.6 N, 0.8 N, 1.0 N, 1.2 N, 1.5 N, 1.8 N, and 2.0 N. In Figure 4, the rate of change in blood flow (amount of change in blood flow / amount of change in pressing pressure) was calculated for five subjects in the ranges of 0.4 N to 0.6 N, 0.6 N to 0.8 N, 0.8 N to 1.0 N, 1.0 N to 1.2 N, 1.2 N to 1.5 N, 1.5 N to 1.8 N, and 1.8 N to 2.0 N. For subjects 1 to 3 in Figures 3 and 4, the measurement probe was attached to the ankle, and for subjects 4 and 5, the measurement probe was attached to the forearm.

[0033] As shown in Fig. 3 and Fig. 4, it was shown that the measured blood flow rate changes when the pressing pressure of the measurement probe against the skin surface changes. In addition, it was shown that the measured blood flow rate increases when the pressing pressure of the measurement probe against the skin surface is in the range of 0.8N to 1.2N, and that in these ranges (0.8N to 1.0N and 1.0N to 1.2N), the rate of change of the blood flow rate when the pressing pressure is changed is small (5% or less). That is, in this embodiment, it was shown that accurate and stable blood flow measurement is possible by setting the pressing pressure of the measurement probe 10 against the skin surface in the range of 0.8N to 1.2N.

[0034] The blood flow meter 1 according to the embodiment of the present invention described above provides the following effects.

[0035] (1) The blood flow meter 1 is provided with a measurement probe 10 having an irradiation unit 111 for irradiating a laser beam toward the skin surface (tissue surface), a light receiving unit 112 for receiving reflected light and scattered light from the skin surface (tissue surface), a pressure sensor 113 for measuring the pressing pressure against the skin surface (tissue surface), and a temperature sensor 114 for measuring the temperature of the skin surface (tissue surface). This makes it possible to measure the blood flow rate under constant conditions for each patient with respect to the pressing pressure and temperature of the skin surface (tissue surface), and to evaluate the treatment effect.

[0036] (2) The blood flow meter 1 is provided with an alarm unit 23 and a control unit 24 that operates the alarm unit 23 to notify that blood flow measurement is possible when the pressing pressure measured by the pressure sensor 113 is within a predetermined pressure range and the temperature of the skin surface (tissue surface) measured by the temperature sensor 114 is within a predetermined temperature range. This makes it possible to easily adjust the pressing pressure and temperature of the skin surface (tissue surface) as the measurement site to within a predetermined range, and to measure the blood flow with stable accuracy. Therefore, the blood flow can be measured under constant conditions for the pressing pressure and temperature of the skin surface (tissue surface) for each patient, and the treatment effect can be evaluated.

[0037] (3) The measuring probe 10 is provided with a heating mechanism for heating the tissue surface. This makes it possible to easily adjust the temperature of the skin surface (tissue surface) to a predetermined temperature range.

[0038] (4) Notification unit 23 includes pressure notification unit 231 that notifies whether the pressing pressure measured by pressure sensor 113 is within a predetermined pressure range, and temperature notification unit 232 that notifies whether the tissue surface temperature measured by temperature sensor 114 is within a predetermined temperature range. This allows the operator to easily grasp the respective states of the pressing pressure and the skin surface temperature, making it easy to adjust the pressing pressure and the skin surface temperature.

[0039] (5) The control unit 24 is controlled to irradiate the laser light from the irradiation unit 111 and start measuring the blood flow rate after a certain time has elapsed since the pressing pressure measured by the pressure sensor 113 falls within a predetermined pressure range and the temperature of the tissue surface measured by the temperature sensor 114 falls within a predetermined temperature range. This makes it possible to measure the blood flow rate without the operator having to operate a measurement start / stop button or the like.

[0040] Next, a second embodiment of the present invention will be described. In the blood flow meter of the second embodiment, the measurement probe and the main body are configured to be detachable. The measurement probe is provided with an alarm unit and a control unit. More specifically, the measurement probe includes a probe main body (not shown) having a similar configuration to the measurement probe in the first embodiment, and a probe adaptor (not shown) having an alarm unit and a control unit. The probe main body and the probe adaptor may be configured as an integral body, or may be configured as separate detachable bodies.

[0041] According to the second embodiment, in addition to the same effects as those of the first embodiment, the following effects are achieved. (6) The measurement probe is configured to include a notification unit and a control unit. As a result, by replacing only the measurement probe with a conventional blood flow meter, it is possible to measure the blood flow rate under constant conditions for each patient with respect to the pressure and temperature on the skin surface (tissue surface), and to evaluate the effectiveness of treatment. (7) The measurement probe is configured to include a probe main body and a probe adaptor that is detachable from the probe main body. This allows the measurement probe, which is detachable from the blood flow meter, to continue using the probe adaptor having the notification unit and the control unit while replacing the probe main body as a consumable item depending on the person being measured. Therefore, the blood flow meter can be used for many people by reusing the probe adaptor and replacing only the probe main body, thereby reducing the maintenance costs of the blood flow meter.

[0042] Although the preferred embodiments of the blood flow meter of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be modified as appropriate. For example, although the case where the blood flow rate is measured at the surface of the skin as the measurement site has been described as an example, the present invention is also applicable to the case where the blood flow rate is measured at the surface of the digestive tract mucosa. [Explanation of symbols]

[0043] 1 Blood flow meter 10 Measuring probe 11 Head 12 Cable 20 Main body 21 Control section 22 Display section 23. Information Department 24 Control Unit 110 Opening 111 Irradiation unit 112 Light receiving part 113 Pressure Sensor 114 Temperature Sensor

Claims

1. A blood flow meter comprising: a measuring probe for measuring a blood flow rate by contacting the probe with a tissue surface; a notification unit for notifying whether the blood flow rate can be measured; and a control unit for operating the notification unit, The measuring probe comprises: An irradiation unit that irradiates laser light toward a tissue surface; a light receiving unit that receives reflected light and scattered light from a tissue surface; A pressure sensor for measuring a pressing pressure against a tissue surface; a temperature sensor for measuring a temperature of a tissue surface; The control unit activates the notification unit to notify that blood flow measurement is possible when the pressing pressure measured by the pressure sensor falls within a predetermined pressure range and the temperature of the tissue surface measured by the temperature sensor falls within a predetermined temperature range.

2. Further comprising an environmental temperature sensor for measuring a temperature around the blood flow meter; 2. The blood flow meter according to claim 1, wherein the predetermined temperature range is set to a range in which a difference between the temperature measured by the environmental temperature sensor and the predetermined temperature range is equal to or smaller than a predetermined value.

3. The notification unit is a pressure notification unit that notifies whether the pressing pressure measured by the pressure sensor is within a predetermined pressure range; a temperature notification unit that notifies whether the temperature of the tissue surface measured by the temperature sensor is within a predetermined temperature range; The blood flow meter according to claim 1 or 2, comprising:

4. The blood flow meter according to any one of claims 1 to 3, wherein the control unit starts measuring the blood flow rate by controlling the irradiation unit to irradiate laser light after a certain time has elapsed after the pressing pressure measured by the pressure sensor falls within a predetermined pressure range and the temperature of the tissue surface measured by the temperature sensor falls within a predetermined temperature range.

5. 5. The blood flow meter according to claim 1, wherein the predetermined pressure range can be set to any value within a range of 0.3N to 1.5N.

6. 6. The blood flow meter according to claim 1, wherein the predetermined pressure range can be set to any value within a range of 0.8N to 1.2N.

7. 7. The blood flow meter according to claim 1, wherein the predetermined temperature range can be set to any value within a range of 10° C. to 40° C.

8. A measuring probe for use in a blood flow meter for measuring blood flow rate by contacting the tissue surface, comprising: An irradiation unit that irradiates laser light toward a tissue surface; a light receiving unit that receives reflected light and scattered light from a tissue surface; A pressure sensor for measuring a pressing pressure against a tissue surface; a temperature sensor for measuring the temperature of the tissue surface; a notification unit that notifies whether or not blood flow can be measured; A control unit that activates the notification unit, The control unit of the measurement probe activates the notification unit to notify that blood flow measurement is possible when the pressing pressure measured by the pressure sensor falls within a predetermined pressure range and the temperature of the tissue surface measured by the temperature sensor falls within a predetermined temperature range.

9. Further comprising an environmental temperature sensor for measuring a temperature around the measurement probe, 9. The measurement probe according to claim 8, wherein the predetermined temperature range is set to a range in which a difference between the temperature measured by the environmental temperature sensor and the predetermined temperature range is equal to or smaller than a predetermined value.

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