Deep-body temperature estimation method and deep-body temperature estimation device

Abstract

To provide a novel method and device that can estimate deep-body temperature safely and with high accuracy.SOLUTION: A deep-body temperature estimation method includes a heat flux acquisition step for obtaining the heat fluxes (q1, q2; q1>q2) of the biological skin tissue using two heat flux sensors having thermal resistances significantly lower than that of the biological skin tissue (Rt), with different thermal resistance characteristics (Rt>>R1, R2<<1; R1<R2); a skin temperature acquisition step for obtaining skin surface temperatures immediately under the two heat flux sensors (Ts1, Ts2; TS1<TS2); and a calculation step for using the heat fluxes (q1, q2) and the skin surface temperatures (Ts1, Ts2) to calculate deep-body temperature (TB) by the formula (1) below.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method and apparatus for estimating core body temperature in animals, primarily humans.

[0002] Body core temperature (BCT), which generally refers to the temperature within the thoracic, abdominal, and brain cavities, is one of the important parameters used to assess health status.

[0003] The true BCT in humans is the temperature of the thermoregulatory center in the hypothalamus of the diencephalon, but its measurement is practically impossible, either directly or indirectly. Therefore, as an alternative to BCT, deep body temperature (DBT) can be used, which is the temperature in the esophagus, axilla, tympanic membrane, gastrointestinal tract, rectum, pulmonary artery, etc. Various types of contact or non-contact temperature probes such as thermistors, thermocouples, or thermal infrared sensors are used to measure DBT.

[0004] Non-invasive, accurate and reliable measurement of DBT from the skin surface is the most desirable goal, and such measurement is extremely important not only for temperature management in clinical settings, but also in home medical care, basal body temperature management for women, sports science, etc. In particular, heat stroke caused by an increase in DBT is a serious problem for outdoor workers, astronauts, racing car drivers, athletes, etc., and coupled with recent global warming, simple, accurate and reliable DBT measurement is becoming an increasingly important issue.

[0005] One of the factors that makes it difficult to determine DBT using conventional temperature measurements is the existence of thermal resistance in skin tissue, which acts as a barrier against the external thermal environment. This is the thermal resistance between the skin surface and the deep tissue (mainly muscle tissue), which is the heat source (hereinafter referred to as "skin thermal resistance (R t ) and, if this is known, an accurate DBT estimate can be determined. There have been several studies on measuring the thermal properties of biological tissue, but because thermal properties differ depending on the part of the body and the state of blood circulation in the skin tissue, the skin thermal resistance (Rt ) is very difficult to determine.

[0006] The first attempt to estimate the temperature of deep tissue from the skin surface was made by Fox & Solman in 1971 (see Non-Patent Document 1). They proposed a new DBT measurement method called the "zero heat flux (ZHF) method (hereinafter also referred to as the "heat flow compensation method"). This method is based on the principle that if a heater is attached to the insulating material placed on the skin surface to control the heat flux that is dissipated to the outside world through the skin and make it zero, DBT and the heated skin temperature will be equal.

[0007] Recently, Kitamura et al. have devised a "dual heat flux (DHF) method" that does not use a heater (see Non-Patent Document 2). This method uses two insulating materials of different thicknesses, measures the temperature difference between two points in the thickness direction of each insulating material, and calculates the skin thermal resistance (R t This is a method to estimate DBT through calculation even if you do not know the [Prior art documents] [Non-patent literature]

[0008] [Non-Patent Document 1] Fox,RH& Solman,AJA new technique for monitoring the deep body temperature in man from the intact skin surface.J.Physiol.(Lond).212,8P-10P(1971) [Non-Patent Document 2] Kitamura, K., Zhu, Summary of the Invention [Problem to be solved by the invention]

[0009] In the ZHF method described in Non-Patent Document 1, a heater is brought into direct contact with the skin, which may cause low-temperature burns and requires a considerable amount of electricity.

[0010] In addition, the DHF method described in Non-Patent Document 2 does not require a heater to control the heat flux, but it is necessary to accurately measure and determine the thermal resistance of each insulator in the probe in advance. In addition, attaching a thermal insulator probe to the skin surface disrupts the heat flux distribution from deep tissues, resulting in temperature estimation errors.

[0011] In view of the above circumstances, an object of the present invention is to provide a new method and device capable of estimating deep body temperature safely and with high accuracy. [Means for solving the problem]

[0012] In order to address these technical and methodological issues, such as the presence of a heater in the ZHF method, the high-precision prior measurement of the thermal resistance of the thermal insulator in the DHF method, and the estimation error due to the disturbance of the heat flux distribution in the tissue, the inventors have used two highly sensitive heat flux sensors with very small and different thermal resistances to calculate DBT and skin thermal resistance (R t Hereinafter, this method will be referred to as the "heat flux ratio (HFR) method."

[0013] To examine the validity and estimation accuracy of this new method, we conducted an in vitro experiment using a phantom model that mimicked living tissue, and an in vivo experiment on humans in which we simultaneously compared the method of the present invention with the sublingual temperature as a reference body temperature. To our surprise, we were able to measure deep body temperature with a sufficiently reliable accuracy. The present invention was completed based on these successful examples and findings.

[0014] The following specifically shows the explanation for deriving the theoretical formula for estimating deep body temperature according to the present invention. The principle of estimating deep body temperature (DBT) is based on the following thermodynamic equilibrium formula (a) for a heat conductor.

[0015] ΔT = R × q Formula (a) (In the formula, ΔT [°C] is the temperature difference between two points of the heat conductor, R [m 2 °C / W] is the thermal resistance, and q [W / m 2 is the heat flux.)

[0016] Fig. 1 shows a schematic diagram of the measurement principle. Fig. 1 shows that two different and very low thermal resistance (R1, R2 << 1; R1 < R2) heat flux sensors (HFS-1, HFS-2) are arranged on the skin surface, and the heat flux generated in the deep body tissue (heat source; temperature T B ) is flowing vertically from the skin tissue to the outside world through each sensor, as indicated by the thick arrows.

[0017] Also, HFS-1 and HFS-2 are very thin, and their thermal resistance is considered negligible compared to the skin thermal resistance (R t ) between the skin surface and the deep tissue (R t >> R1, R2). Therefore, the temperature difference caused by the heat flux passing through each sensor is negligibly small, and the temperature of each sensor can be regarded as the skin surface temperature. This is also effective in reducing the disturbance of the heat flux distribution throughout the deep tissue.

[0018] Under the above conditions, if the heat fluxes obtained by HFS-1 and HFS-2 are q1 and q2 (q1 > q2) respectively, the following formulas (b) and (c) hold.

[0019] T B -T S1 = R t × q1 Formula (b) T B -T S2 = R t × q2 Formula (c) (In the formula, T Bis the deep body temperature (DBT) and T S1 and T S2 (T S1 <T S2 ) are the skin surface temperatures directly beneath HFS-1 and -HFS2, respectively.

[0020] From equation (b) and equation (c), R t Erase and put T B This gives the following equation (1).

[0021] T B =(K / (K-1))×T S2 -(1 / (K-1))×T S1 Formula (1) (In the formula, K is the heat flux ratio (= q1 / q2>1).)

[0022] Also, subtract formula (b) from formula (c), or use the T obtained from formula (1) B By using t can be calculated from the following formula (2-1) or formula (2-2).

[0023] R t =(T S2 -T S1 ) / (q1-q2) Equation (2-1) Or, R t =(T B -T S1 ) / q1=(T B -T S2 ) / q2 formula (2-2)

[0024] Equation (1) is the skin surface temperature T obtained by HFS-1 and HFS-2. S1 and T S2 and the heat flux ratio (K=q1 / q2) were measured simultaneously. B This means that you can ask for

[0025] Thus, according to one aspect of the present invention, there is provided the following: [1] Thermal resistance of skin tissue (R t ) and have different thermal resistances (Rt A heat flux acquisition step of obtaining the heat fluxes (q1, q2; q1 > q2) of the skin tissue of a living body by two heat flux sensors having >>R1, R2<<1; R1 < R2), the skin surface temperature (T s1 , T s2 ; T S1 < T S2 ) under the two heat flux sensors, a skin temperature acquisition step of obtaining the skin temperature, and an arithmetic step of calculating the deep body temperature (T s1 , T s2 ) by the following formula (1) using the heat fluxes (q1, q2) and the skin surface temperature (T B ). A deep body temperature estimation method having . TIFF2024169254000002.tif39155[2] In the arithmetic step, further calculating the thermal resistance (R s1 , T s2 ) of the skin tissue by the following formula (2) using the heat fluxes (q1, q2) and the skin surface temperature (T t ). The method according to [1]. TIFF2024169254000003.tif31134[3] The two heat flux sensors are arranged adjacent to each other. The method according to [1] or [2]. [4] A heat flux acquisition unit that is sufficiently smaller than the thermal resistance (Rt) of the skin tissue of a living body and obtains the heat fluxes (q1, q2; q1 > q2) of the skin tissue of a living body by two heat flux sensors having different thermal resistances (R t >>R1, R2<<1; R1 < R2), a skin temperature acquisition unit that obtains the skin surface temperature (T s1 , T s2 ; T S1 < T S2 ) under the two heat flux sensors, and a deep body temperature calculation unit that calculates the deep body temperature (T s1 , T s2 ) by the following formula (1) using the heat fluxes (q1, q2) and the skin surface temperature (T B ). A deep body temperature estimation device having . TIFF2024169254000004.tif37153[5] In the deep body temperature calculation unit, the heat flux (q1, q2) and the skin surface temperature (T s1 ,T s2 ) and the thermal resistance of the skin tissue (R t The apparatus according to [4], further calculating TIFF2024169254000005.tif33138[6] The apparatus described in [4] or [5], wherein the two heat flux sensors are positioned in close proximity. Effect of the Invention

[0026] According to the present invention, deep body temperature can be estimated safely and with high accuracy. [Brief description of the drawings]

[0027] [Figure 1] This is a diagram showing the principle of core body temperature estimation using the heat flux ratio (HFR) method. [Diagram 2] FIG. 2 is a schematic explanatory diagram showing an example of the configuration of a heat flux sensor unit in the device of the present invention. [Diagram 3] 1 is a block diagram showing an example of a configuration of an apparatus according to the present invention; [Figure 4] FIG. 2 is a schematic diagram showing the configuration of a skin tissue phantom in Experimental Example 1. [Diagram 5] FIG. 1 is a correlation diagram between the actually measured temperature TD in Experimental Example 1 and the estimated temperature TD* by the method of the present invention. [Figure 6] FIG. 13 is a diagram showing measurement sites in Experimental Example 2. [Figure 7] FIG. 11 is a correlation diagram between sublingual temperature Tsub in Experimental Example 2 and estimated temperature TB* by the method of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Hereinafter, the embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments.

[0029] The deep body temperature estimation method of the present invention uses two heat flux sensors with heat resistances (R t ) that are sufficiently smaller than the heat resistance (R t ) of the skin tissue of the living body and have different heat resistances (R t >>R1,R2<<1;R1<R2) to obtain the heat fluxes (q1,q2;q1>q2) of the skin tissue of the living body in a heat flux acquisition step, and obtains the skin surface temperatures (T s1 ,T s2 ;T S1 <T S2 ) directly below the two heat flux sensors in a skin temperature acquisition step, and uses the heat fluxes (q1,q2) and the skin surface temperatures (T s1 ,T s2 ) to calculate the deep body temperature (T B ) by the above formula (1) in a calculation step.

[0030] (Heat flux acquisition step) In the heat flux acquisition step, the heat fluxes [W / m 2 of the skin tissue of the living body are acquired by two heat flux sensors.

[0031] The two heat flux sensors have heat resistances that are sufficiently smaller than the heat resistance (R t ) of the skin tissue of the living body and have different heat resistances (R t >>R1,R2<<1;R1<R2). Specifically, the heat resistances (R1,R2) of the heat flux sensors can be, for example, 0.00015 [m 2 ℃ / W] to 0.00022 [m 2 ℃ / W]. The difference in the heat resistances of the two heat flux sensors is not particularly limited as long as the problems of the present invention can be solved, but is, for example, about 0.00007 [m 2 ℃ / W]. Note that the heat resistance (R t ) of the skin tissue of the living body varies depending on the measurement site. For example, when the measurement site is the chest wall or the back of the neck (nape), if the thickness of the skin tissue from the epidermis to the subcutaneous tissue (fat layer) is 10 mm to 25 mm and the effective thermal conductivity of the tissue is 0.3 to 0.5 W / m℃, then R t = 0.03 to 0.09 m 2 ℃ / W.

[0032] In the present invention, the living body refers to a mammalian body such as a human, a horse, a dog, a cat, etc., and is preferably a human body. The measurable sites are not particularly limited, but examples thereof include the chest wall, the upper abdomen, the back of the neck (nape), and the temples.

[0033] The two heat flux sensors are preferably disposed close to each other at the measurement point, and for example, the distance between the two heat flux sensors is about 8 mm to 12 mm.

[0034] (Skin temperature acquisition process) In the skin temperature acquisition process, the skin surface temperature (T s1 ,T s2 ;T S1 <T S2 ) to get the The temperature sensor for measuring the skin surface temperature is not particularly limited, but examples thereof include contact type temperature sensors such as thermistors and thermocouples. In addition, the heat flux acquiring step and the skin temperature acquiring step may be performed simultaneously as long as a thermal equilibrium state is reached, or either the heat flux acquiring step or the skin temperature acquiring step may be performed first.

[0035] (calculation process) In the calculation step, an estimate of the core body temperature is calculated. The heat flux (q1, q2) acquired in the heat flux acquisition process and the skin surface temperature (T s1 ,T s2 ) and the deep body temperature (T B ) to obtain an estimate of

[0036] In the calculation step, the heat flux (q1, q2) acquired in the heat flux acquisition step and the skin surface temperature (T s1 ,T s2 ) and the thermal resistance of the skin tissue (R t ) can be calculated.

[0037] In the method of the present invention, as long as a heat flux acquisition step, a skin temperature acquisition step, and a calculation step are performed, various steps and operations can be appropriately added before, after, and / or during each step as long as the problems of the present invention can be solved. Examples of these steps include, for example, a step of outputting estimated values (core temperature (T B ), skin thermal resistance (R t )) calculated by a calculation step and displaying them on a liquid crystal display or the like, or a step of transmitting an estimated value (core temperature (T B ), skin thermal resistance (R t )) signal to an external device may also be included.

[0038] The core temperature estimation device of the present invention includes two heat flux sensors having heat resistances (R t ) that are sufficiently smaller than the thermal resistance of the skin tissue of a living body and different heat resistances (R t >>R1, R2<<1; R1 < R2), and a heat flux acquisition unit that obtains the heat fluxes (q1, q2; q1 > q2) of the skin tissue of the living body, and skin surface temperatures (T s1 , T s2 ; T S1 < T S2 ) directly below the two heat flux sensors, and a calculation unit that calculates the core temperature (T s1 , T s2 ) using the heat fluxes (q1, q2) and the skin surface temperatures (T s1 , T s2 ) according to the above formula (1).

[0039] Specifically, the core temperature estimation device of the present invention includes a heat flux acquisition unit, a skin temperature acquisition unit, and a processing unit including a control unit, a storage unit, and a calculation unit, and may include, for example, a display unit. The heat flux acquisition unit includes two heat flux sensors having heat resistances (R t ) that are sufficiently smaller than the thermal resistance of the skin tissue of a living body and different heat resistances (R t >>R1, R2<<1; R1 < R2) for obtaining the heat fluxes (q1, q2; q1 > q2) of the skin tissue of the living body. The skin temperature acquisition unit measures the skin surface temperatures (T s1 , T s2 ; T S1 < TS2 The temperature sensors may be integrated with the heat flux sensor to measure the temperature directly below the heat flux sensor, but are not limited to this. The control unit is an arithmetic and control device consisting of an MPU, a CPU, etc. The storage unit is a storage device composed of RAM, ROM, and the like. The calculation unit calculates the heat flux (q1, q2; q1>q2) obtained from the heat flux acquisition unit and the skin surface temperature (T s1 ,T s2 ;T S1 <T S2 ) and the deep body temperature (T B In the device of the present invention, the function of the calculation unit is realized by the control unit executing a program stored in the storage unit. The display unit is, for example, a display device such as a liquid crystal display.

[0040] FIG. 2 is a schematic explanatory view showing an example of the configuration of a heat flux sensor unit in the device of the present invention. Heat flux sensor unit (SU-1, SU-2: size (example) 23 x 23 x 3.7 mm 3 ) is equipped with heat flux sensors (HFS-1, HFS-2). This heat flux sensor unit (SU) has a built-in T-type thermocouple element for temperature measurement, that is, a temperature sensor for measuring the skin surface temperature directly under the heat flux sensor.

[0041] The heat flux sensor (HFS) may be, for example, "HF-20" (manufactured by Captec Enterprise, size: 20×20 mm, thickness: 0.4 mm, accuracy: ±3%, response time: approximately 0.3 seconds). This heat flux sensor (HFS) has a very small thermal resistance (e.g., 0.00015 m) compared to the thermal resistance of skin tissue of a living body. 2 °C / W).

[0042] In general, skin thermal resistance (R t) varies greatly depending on the difference in thickness between the skin surface and the core (deep) tissue that functions as a heat source in each part of the body, the state of blood circulation in the tissue, etc., and R t It is difficult to specify the value. However, the approximate value can be calculated from the literature as follows: In other words, if the measurement site is the chest wall or the back of the neck (nape), the thickness of the skin tissue from the epidermis to the subcutaneous tissue (fat layer) is 10mm to 25mm, and the effective thermal conductivity of the tissue is 0.3 to 0.5W / m℃, R t =0.03~0.09m 2 °C / W. In other words, the thermal resistance of the HFS used in the experimental example described below is sufficiently small compared to the thermal resistance of skin tissue.

[0043] It is desirable to attach aluminum foil having a thickness of, for example, about 10 μm to both sides of each HFS to block the effects of external thermal radiation.

[0044] In the sensor unit SU-1, for example, it is preferable to attach highly heat-conductive gel sheets (manufactured by Fuji Polymer Industries Co., Ltd.) having a thickness of about 1 mm to both sides of the HFS-1 for fixing and protecting the HFS-1. In the sensor unit SU-2, for example, it is preferable to fix a conductive gel sheet to the skin contact surface and to place a heat insulating sheet (a foamed polyurethane sheet: manufactured by Fuji Rubber Industries Co., Ltd.) having a thickness of about 1 mm to 1.5 mm on the other surface in order to slightly increase the thermal resistance (R2) of SU-2 compared to the thermal resistance (R1) of SU-1.

[0045] Each sensor unit is preferably fixed around the periphery by a frame made of, for example, a thermal interface silicone material (manufactured by Fuji Polymer Industries Co., Ltd.), and further covered with a polypropylene film (manufactured by Fuji Polymer Industries Co., Ltd.) having a thickness of approximately 0.2 mm.

[0046] The weight of each sensor unit is, for example, about 3 g. When the thermal equilibrium time of the sensor unit was measured in a preliminary experiment in the experimental example described later, it was confirmed that the thermal equilibrium time was less than 3 to 4 minutes for a temperature rise from 25°C to 30°C, and the heat capacity of the sensor unit was also small.

[0047] Figure 3 shows the block diagram of the measurement system. The output signals (q1, T S1 ;q2, T S2 ) is input to a microprocessor (MPU) via an amplifier for measuring heat flux (e.g., OPA2277, manufactured by Texas Instruments Inc.) and an amplifier for measuring skin temperature (e.g., MAX31856, manufactured by Analog Devices Inc.).

[0048] In the MPU, for example, each signal is sampled at 1 second intervals by a 16-bit A / D converter and averaged at any time. The data can be stored in, for example, a 16GB micro SD card.

[0049] The detection sensitivity of HFS-1 and HFS-2 is S1 = 3.79 V / (W / m 2 ), S2 = 3.84μV / (W / m 2 ) and the amplification factor of the heat flux amplifier can be 1000 times.

[0050] The temperature output from a T-type thermocouple (temperature sensor) built into each HFS is detected by a thermocouple amplifier (e.g., MAX31856) with a temperature resolution of less than 0.008°C and an accuracy of less than 0.15%. EXAMPLES

[0051] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0052] [Experimental Example 1: In vitro experiment] In order to evaluate the validity and temperature estimation accuracy of the deep body temperature estimation method of the present invention, an in vitro experiment was carried out using a phantom model simulating biological tissue, as shown in FIG.

[0053] The sensor units (SU-1 and SU-2) were placed about 10 mm apart on a polyurethane foam rubber plate (manufactured by Fuji Polymer Industries, Ltd.) that simulated skin tissue in order to minimize the disturbance of the heat flux distribution. tr ) is the thermal resistance of the skin tissue (R t ) was selected. In addition, the thickness of the rubber plate was changed to evaluate the deep temperature estimation error due to the change in thermal resistance. Based on the above considerations, rubber plates with nominal thicknesses (NT) of 2 mm, 3 mm, and 5 mm were selected for the experiment.

[0054] The deep temperature was measured using a uniform temperature heater (silicone rubber heater, 100 × 200 × 1.5 mm) placed on the base. 3 An aluminum plate (thickness 1.5 mm) was fixed on top of a heat source (Kawai Electric Manufacturing Co., Ltd.) and the temperature was controlled in the range of about 35 to 43°C by a precision temperature controller (TJA-550: AS ONE Co., Ltd.). The controlled temperature was an unknown deep temperature value (T D The temperature was measured using a high-precision thermometer ("DS103", accuracy: ±0.02°C, resolution: 0.001°C in the range of 0 to 50°C, manufactured by Nitto Kogyo Co., Ltd.) as the temperature sensor. This device used a high-precision thermistor probe (SXK-67, φ1 diameter, manufactured by Nitto Kogyo Co., Ltd.) calibrated by the manufacturer at a constant temperature defined in the International Temperature Scale of 1990 (ITS-90). Prior to the experiment, the surface temperature of the aluminum plate was measured at five points, and the temperature uniformity within 0.01°C was confirmed.

[0055] The experimental conditions were T in seven steps of about 1°C in the range of about 35.5 to 43°C. D The estimated T calculated by the above formula (1) is D (T D * The thermal equilibrium time for this phantom model was about 5 minutes, and each experiment was performed at T D After changing the temperature, the sensor unit and the phantom model were allowed to reach thermal equilibrium. The experiment was performed under conditions of nominal thicknesses of the rubber plate NT = 2 mm, 3 mm, and 5 mm, and 21 sets of experimental data were obtained in total. The room temperature during the experiment was 25°C. The results are shown in Table 1 and FIG.

[0056] [Table 1]

[0057] Table 1 shows the measured parameters (T D , T S1 , T S2 , q1, q2), and the calculated variables (K, T D * , R tr The table shows the difference between the actual temperature measurement and the estimated value (T D -T D * ) mean absolute error (MAE) and standard error of the mean (SEM), and R tr The mean and SEM of the values ​​are shown.

[0058] Figure 5 shows the actual T D Value and Estimated T D * This graph shows the correlation between the values ​​and the NT value, with NT as a parameter. The ■ marks in the graph are plots for NT = 2 mm, the ▲ marks are plots for NT = 3 mm, and the ● marks are plots for NT = 5 mm. The graph also shows the linear regression equation and the coefficient of determination (R 2 ) and correlation coefficient (γ). Regardless of the change in the thickness of the rubber plate, i.e., the thermal resistance of the rubber plate, T D and T D * It can be seen that there is a very high linear correlation.

[0059] [Experimental Example 2: In vivo experiment] The suitability and accuracy of the core body temperature measuring method of the present invention for use in humans was evaluated through in vivo testing.

[0060] In order to conduct this experiment, a research briefing session was held to recruit participants. After detailed explanations of the research content and the measurement sites, participants agreed to place the sensor unit on the upper left chest wall or the back of the neck (nape) (see Figure 6). In addition, participants accepted the traditionally used sublingual or axillary temperature measurement sites as the control for temperature measurement, but did not accept gastrointestinal or rectal temperature measurements, which are desirable as deep body temperature measurement sites. As a result of the above, nine volunteers (four men and five women) agreed to use sublingual temperature as the control body temperature and signed the research participation consent form. This study was approved by the Ethics Committee of Showa University School of Medicine and the Ethics Committee of Shizuoka Institute of Science and Technology, and was conducted in accordance with the principles expressed in the Declaration of Helsinki.

[0061] All participants were Japanese, aged 15-75 years (40.2 ± 23.4 standard deviation (SD)), and were healthy individuals living normal daily lives. The room temperature was 23-25°C, and the humidity was 40-55%. Subjects were asked to sit in a chair and maintain a relaxed state during the measurements.

[0062] As described above, the sensor units (SU-1, SU-2) were fixed with adhesive tape to the upper left chest or the back of the neck (nape). In order to minimize the disturbance of the heat flux distribution in the skin tissue, which is a concern when attaching the units, the two units were fixed approximately 10 mm apart, as in the in vitro experiment. After attaching the units, 10 to 15 minutes had elapsed, which was estimated to be the time it took to reach thermal equilibrium, and four variables (T S1 , q1;T S2 , q2) were measured. At the same time, the sublingual temperature (T sub ) was measured using a commercially available basal body temperature thermometer (MC-172L, accuracy: ±0.05°C, resolution: 0.01°C, 35 to 38°C, measurement time: approximately 5 minutes; manufactured by Omron Healthcare Co., Ltd.).

[0063] A total of 9 datasets (T S1 , q1, T S2 , q2, T sub ) is obtained, and the core body temperature (T B* ) and sublingual temperature measured by a basal thermometer (T sub ) was compared with the skin tissue thermal resistance (R ts ) was also sought. The results are shown in Table 2 and FIG.

[0064] [Table 2]

[0065] Table 2 shows the variables measured in the in vivo study of nine volunteer subjects (T sub , T S1 , T S2 , q1, q2) and the variables calculated from these (K, T B * , T sub -T B * , R ts ) were summarized for each subject, with gender, body mass index (BMI), and measurement site also shown.

[0066] Figure 7 shows the results of the T sub Value and T B * The graph shows the correlation between the linear regression equation and the coefficient of determination (R 2 ), and the correlation coefficient (γ) also showed a straight line (y=x; solid line). Although the range of change in body temperature was narrow, a good linear correlation was observed between the two. However, the sublingual temperature Tsub value was not as good as the T estimated by this method. B * The results showed a lower value of 0.14 ± 0.02 °C (SEM) than the previous value.

[0067] [Methodological considerations for estimating DBT] The deep body temperature measurement method of the present invention is a deep body temperature (DBT) measurement method based on known thermodynamic principles. The operating principle is to directly measure two heat fluxes (q1, q2) using two sensor units (SU-1 and SU-2) equipped with heat flux sensors (HFS-1 and HFS-2) having very small and different thermal resistances (R1, R2: R1 < R2 << 1), and estimate the DBT from the simultaneously measured skin temperatures (T S1 , T S2 ). At this time, the thermal resistance values R1 and R2 of the sensors are required to be negligibly small (R1, R2 << R t ) compared to the thermal resistance (R t ) of the skin tissue. This also means that it is very effective for the sensor system to accurately detect the heat flux from the skin tissue without disturbing the distribution of the heat flux conducted from the deep tissue (regarded as a heat source) through the skin tissue.

[0068] The thermal resistance of the HFS of SU-1 employed in this experiment was R1 = 0.00015 m 2 ℃ / W, and for the HFS of SU-2, the thermal resistance R2 was slightly increased by installing a thin heat insulating material (foamed polyurethane sheet) on its surface. Although the thermal resistance R2 can be roughly estimated using the heat flux ratio K (= q1 / q2), it is considered that there are variations as shown in Tables 1 and 2 due to the non-uniformity of the urethane sheet material, the magnitude of the heat flux, the temperature, etc. The average values of K for SU-1 and SU-2 used in the in vitro experiment and the in vivo experiment were calculated to be 1.275 (0.0190 S.E.M.) and 1.497 (0.0631 S.E.M.) respectively from Tables 1 and 2, and it can be said that R2 is roughly 30 - 50% larger than R1. Specifically, if the thermal resistance does not depend on the heat flux, the approximate value of R2 is 0.00019 - 0.00022 m 2 ℃ / W.

[0069] In addition, in the case of in vivo experiments, when the values ​​of q1 and q2 are taken into consideration with reference to Table 2, the temperature difference passing through HFS-1 and HFS-2 is less than 0.015°C and 0.015 to 0.017°C, respectively. This shows that the condition that the temperature difference passing through the HFS is very small is almost satisfied, as mentioned above. On the other hand, as mentioned above, the skin thermal resistance R t The true R in humans varies greatly depending on factors such as the thickness of the tissue between the skin surface and the core (deep) tissue (mainly the muscle layer), which is the heat source, and is also dependent on factors such as the blood flow in the skin tissue and the ambient temperature. t The value is still unknown. However, based on previous research reports, it is thought to be between 0.03 and 0.09 m. 2 It can be estimated that the value is about °C / W. This indicates that the thermal resistance of each sensor unit is sufficiently small (less than 1 / 200 to 1 / 400) compared to the tissue thermal resistance, and it can be estimated that the effect of the sensor thermal resistance on the tissue heat flux distribution is very small even if the sensor unit is placed on the skin surface. It is expected that the estimation accuracy of DBT can be improved by using a heat flux sensor with an even smaller thermal resistance, which is also effective in reducing the temperature difference caused by the sensor.

[0070] [On the validity and accuracy of temperature estimation by in vitro experiments] In an in vitro experiment using a simple phantom model with a heater as a heat source and a heat insulating material (urethane rubber plate) that mimics skin tissue, the thermal resistance of the heat insulating material (R tr ) and does not depend on the temperature under the insulation (T D ) and estimated temperature (T D * ) showed very good agreement (see Table 1 and FIG. 5). This result clearly demonstrates the validity of the measurement method of the present invention.

[0071] In this experiment, the thermal resistance of the insulator (R tr ) was changed, but rubber material was selected based on previous research reports so that the value would be similar to the thermal resistance of biological tissue. Table 1 shows the R trThe values ​​are shown for each experiment, and the average value is 0.0402 (SEM: 0.00106) m when NT = 2 mm. 2 ℃ / W, NT=3mm, 0.0658(SEM:0.00077)m 2 ℃ / W, NT=5mm, 0.1089(SEM:0.00302)m 2 ℃ / W. R for each NT value tr Although slight variations in values ​​were observed, the values ​​were within the range of the tissue thermal resistance estimated in advance (0.03 to 0.09 m 2 ℃ / W), and was close to the skin thermal resistance (R ts ) (see Table 2) is noteworthy.

[0072] Here, the above R calculated by the above formula (2) tr The thermal resistance of the rubber sheet (R r Theoretically, the thermal resistance (R r [m 2 °C / W], the following equation (d) holds in a state of thermal equilibrium.

[0073] R r =d / λ Equation (d) (In the formula, λ [W / m℃] is the thermal conductivity of the plate.)

[0074] It is known that the effective thermal conductivity of polyurethane foam varies depending on the foaming form, the uniformity of the foaming, and the external environment (ambient temperature, radiation temperature, convection, etc.). Therefore, referring to past research papers, the thermal resistance (R tr *) was calculated using formula (d). According to a research report by Soloveva et al. (Soloveva, OV, Solovev, SA, Vankof, YV & Rozalina, Z. Experimental studies of the effective thermal conductivity of polyurethane foams with different morphologies. Processes 10, 2257, doi:10.3390 / pr10112257(2022)), the λ value of commonly used polyurethane foam is approximately 0.0450 W / m°C at around 37°C. If this value is taken as λ and the NT value is taken as d (the thickness between the upper surface of the rubber plate as the heat source and the upper surface of the aluminum plate), R tr * =0.0444m 2 ℃ / W(d=2×10 -3 m), R tr * =0.0667m 2 ℃ / W(d=3×10 -3 m), R tr * =0.1111m 2 ℃ / W(d=5×10 -3 m) These values ​​are the average values ​​R calculated by this method, even if some error in the NT value and the non-uniformity of materials such as foam rubber plates are taken into consideration. tr Although a simple phantom model simulating skin tissue was used, the above experimental results and considerations clearly demonstrate the validity of the present invention, and furthermore, it is believed that this method can be applied to non-destructive measurement of the temperature inside a pipe in a fluid pipe transport system and to thermal resistance measurement technology in a heat conduction system.

[0075] [DBT estimation by in vivo measurement] Several methods have been developed to estimate deep body temperature (DBT) non-invasively. Except for organ temperature measurement methods used in hyperthermia treatment, there are currently two methods of estimating DBT from the skin surface based on clear measurement principles: the "ZHF method" (Zero Heat Flux Method) and the "Dual Heat Flux Method" (DHF Method). In the former ZHF method, a probe is placed on the upper sternum, and it has been reported that the deep body temperature can be estimated with a difference of approximately 0.2°C by comparing it with rectal temperature, ear canal temperature, or esophageal temperature in three healthy subjects under various environments. In the DHF method, a probe is attached to the left anterior temporal region and a commercially available deep body thermometer based on the ZHF method is placed on the opposite side (right anterior temporal region) to conduct a comparative experiment. The results show good agreement, although the temperature range is narrow, from 36.6 to 37.3°C.

[0076] Naturally, when evaluating the accuracy and validity of a newly conceived or developed DBT measurement system, it is very important to determine the site of the comparative temperature measurement. It would be most desirable to measure the tissue temperature directly below the new sensor probe placed on the skin by a direct (invasive) method, but direct deep temperature measurement is not possible unless research ethics allow for the patient's benefit. Therefore, as an alternative, sites that can be measured by non-invasive methods, such as the axilla, oral cavity, sublingual, tympanic membrane, gastrointestinal tract, rectum, nasopharynx, esophagus, stomach, and bladder, are used. Of these, the tympanic membrane, nasopharynx, and esophagus are said to be the most suitable sites for deep body temperature measurement in clinical settings. However, in this in vivo study, no participants agreed to DBT measurements at these sites, and sublingual temperature measurements were performed on all participants who agreed to body temperature measurements at the axilla, oral cavity, or sublingual. Participants were asked to refrain from eating or drinking for one hour before the experiment, to place the tip of the temperature sensor in a sublingual pocket, and to keep their mouths tightly closed during the measurement.

[0077] Considering these methodological issues, as shown in Table 2 and Figure 7, the results of the in vivo comparison this time are reasonably acceptable, considering that there is an actual difference between the deep body temperature and the sublingual temperature according to the present invention, and that there is an almost constant temperature difference between the two and an almost linear correlation is observed. In general, the rectal temperature is the highest in the body, and the order is rectal temperature > tympanic membrane temperature > sublingual temperature > axillary temperature, and it is known that the specific temperature difference is 0.4 to 0.6°C between the rectal temperature and the tympanic membrane temperature and the sublingual temperature, 0.8 to 0.9°C between the rectal temperature and the axillary temperature, and 0.3 to 0.5°C between the sublingual temperature, the tympanic membrane temperature and the axillary temperature. From the results of this time, it is presumed that the deep body temperature (upper chest, nape) according to the present invention corresponds to a body temperature close to the tympanic membrane temperature.

[0078] [On the possibility of estimating the thermal resistance of the skin] The results of an in vitro experiment using a phantom model showed that the present invention can estimate the thermal resistance of skin tissue. Table 2 shows the skin thermal resistance (R ts ) is also shown. Considering the anatomical structure of the skin tissue, the calculated R ts can be called the average effective value of skin tissue. ts It is known physiologically that skin thermal resistance varies with factors such as deep body temperature, skin blood flow, and changes in the thermal environment. ts It is currently difficult to verify the veracity of the values.

[0079] In general, the thermal resistance of skin tissue is determined by the thickness of the tissue and its thermal conductivity, which depends on the factors mentioned above. It is well known that tissue thickness varies greatly depending on an individual's body mass index (BMI), gender, age, etc., but statistical results show that the thickness of skin tissue (epidermis, dermis, and subcutaneous tissue (fat layer)) in the chest wall and neck area is approximately 10 to 25 mm. On the other hand, according to previous research results, the effective thermal conductivity of tissue has been reported to be 0.3 to 0.5 W / m°C. From these values, R t =0.03~0.09m 2In this in vivo test, the R obtained for each subject at rest in a nearly comfortable indoor environment (room temperature 23-25°C, humidity 40-55%) was ts Values ​​are 0.038 to 0.05 m. 2 ℃ / W (average value 0.0422m 2 °C / W) and the above R t Within the range of values, the effective R ts This can be said to be a sufficiently acceptable estimate. [Industrial Applicability]

[0080] The deep body temperature measuring method and deep body temperature measuring device of the present invention can obtain deep body temperature safely and with high accuracy, and are therefore extremely useful as self-management systems in fields such as medicine and health care, in addition to measurements in clinical settings, in fields such as home medical care and sports science.

Claims

1. Thermal resistance of skin tissue of living body (R ｔ ) and have different thermal resistances (R ｔ >>R １ , R ２ <<1;R １ <R ２ The heat flux (q １ , q ２ ;q １ >q ２ a heat flux acquisition step for obtaining the heat flux; The skin surface temperature (T ｓ１ , T ｓ２ ;T Ｓ１ <T Ｓ２ A skin temperature acquisition step of obtaining a skin temperature; The heat flux (q １ , q ２ ) and the skin surface temperature (T ｓ１ , T ｓ２ ) and the deep body temperature (T Ｂ ) and a calculation step of calculating A method for estimating deep body temperature.

2. In the calculation step, the heat flux (q １ , q ２ ) and the skin surface temperature (T ｓ１ , T ｓ２ ) and the thermal resistance of the skin tissue (R ｔ 2. The method of claim 1, further comprising calculating

3. The method of claim 1 , wherein the two heat flux sensors are positioned in close proximity.

4. Thermal resistance of skin tissue of living body (R ｔ ) and have different thermal resistances (R ｔ >>R １ , R ２ <<1;R １ <R ２ The heat flux (q １ , q ２ ;q １ >q ２ ) a heat flux acquisition unit; The skin surface temperature (T ｓ１ , T ｓ２ ;T Ｓ１ <T Ｓ２ A skin temperature acquisition unit for acquiring a skin temperature; The heat flux (q １ , q ２ ) and the skin surface temperature (T ｓ１ , T ｓ２ ) and the deep body temperature (T Ｂ ) and a calculation unit for calculating A deep body temperature estimation device having the same.

5. In the deep body temperature calculating section, the heat flux (q １ , q ２ ) and the skin surface temperature (T ｓ１ , T ｓ２ ) and the thermal resistance of the skin tissue (R ｔ 5. The apparatus of claim 4, further comprising:

6. The apparatus of claim 4 , wherein the two heat flux sensors are positioned in close proximity.

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