JPS61120026A - Simple deep-part clinical thermometer - Google Patents

Abstract

PURPOSE:To measure the bodily temperature of a deep part without any invasion by arranging temperature sensors at the center positions of the contact surface of a heat insulating material which has relatively small heat conductivity and contacts a living body and an atmospheric contact surface which face the contact surface of the heat of the heat insulating material. CONSTITUTION:A deep-part clinical thermometer 4 consists of the heat insulating material 1 which contacts skin 5, and a sensor 2 for measuring the temperature of a body surface and a sensor 3 for measuring outside air temperature fixed at the center parts of the body surface side of the heat insulating material 1 and air-side surface. Outputs of a bridge circuit 11 including the sensor for body surface temperature measurement and a bridge circuit 13 including the sensor 3 for outside air temperature measurement are amplified by amplifying circuits 12, 14, the output of a subtracting circuit 15 is multiplied by a specific correction value, and the output of a multiplying circuit 16 and the output of the amplifier 14 are added together by an adding circuit 17, whose output is digitized by an A/D converter 18 and displayed on a digital temperature display part 19. Consequently, a value close to the bodily temperature of a deep part is measured without reference to variation in outside temperature.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a thermometer, and relates to a portable long-term monitor of core temperature and peripheral blood circulation, and a highly safe and simple core thermometer that does not cause skin irritation. .

[Background of the invention]

Body temperature fluctuates physiologically depending on age, 9 day differences, 9 individual differences, ovarian cycle 1 fever, etc., and body heat distribution differs depending on location, environment, etc. Normally, the temperature decreases closer to the peripheral body surface, but the center of the body is controlled to maintain a constant temperature called core temperature. Core temperature reflects the physiological state well, and the significance of its measurement is well known.

Since it is impossible to directly measure the blood temperature at the aortic outlet, which is representative of the core temperature, on a daily basis, the rectal temperature, which is close to this, or the axillary temperature, 9 oral temperature, or the axillary temperature is measured with a mercury thermometer, or a child thermometer. It is called. Rectal temperature is the temperature inside the body cavity, and from the point of view of accuracy it reflects the core temperature well, but it is not used on a daily basis for reasons such as discomfort 1 and contamination of thermometers.

Also, the oral temperature is 0.4 to 0.6C, and the axillary temperature is 0.
．． 8-0.9 tl: 'Low (Akira Nakano - Author: Illustrated Physiology.

Igakushoin, 1981), and is often used clinically because it is a simple method. However, it is not suitable for long-term temperature monitoring.

In the skin, the body temperature gradually rises from the skin surface to approximately 2
At a depth of cm, it becomes a nearly constant value of 36.5 to 37.5C. That is, the internal high-temperature layer is surrounded by a low-temperature layer with a thickness of about 2 crr1 (first layer). Therefore, a deep body thermometer was devised, and by using the heat flow compensation method, the deep tissue temperature of each part of the body can be measured, especially continuous measurement, and the core temperature and peripheral blood flow state can be known (Japanese Patent Application Laid-Open No. 55-29794).

This conventional core thermometer is shown in the fourth prisoner. This sensor includes a heat insulating layer 8 having a low conductivity, and a heat insulating layer 8 having a low thermal conductivity that surrounds the periphery of the heat insulating layer 8 except for the surface facing the living body to be measured, and contacts the surface of the living body to be measured at the peripheral edge. A large heat transfer layer 6, a heating element layer 7 fixed to the surface of the heat transfer layer 60, a measuring temperature top/suction 9 disposed at a central position on the contact surface side of the heat insulating layer 8, and a heat transfer layer. It consists of a heating element fixed to the heat insulating layer 8 side of 6/117 and a temperature sensor 10 for controlling heat generation. A core thermometer incorporating a heat source in this method is placed on the body surface, and the heat flow conducted from the heat source to the living body cancels the heat flow transmitted from the living body to the core thermometer, and the heat flow between the body's core temperature and the skin 5 between the core thermometer is The heat flow compensation method t' principle is used to detect the deep temperature at the body surface by setting the gradient to zero. Therefore, electric power (several W) is required to heat the heater,
It is disadvantageous for long-term monitoring as a portable device, and there is a problem of skin irritation due to excessive power supply due to failure of the heater control circuit, or a fail-safe system is required. Further, when measuring intermittently while the sensor is worn for a long period of time, even with the heater control circuit tOH, there is a problem in that it takes 15 to 20 minutes to measure due to the heat capacity of the skin and the sensor.

[Purpose of the invention]

The purpose of the present invention is to provide low power consumption and thermal safety, to easily measure an approximate value of the body's core temperature without being greatly affected by temperature, and to provide a long-term portable moss for measuring core temperature and peripheral blood circulation. To provide a core thermometer that can instantly measure body temperature when necessary.

[Summary of the invention]

In the present invention, if a heat insulating material with a thermal conductivity similar to that of the skin is closely attached to the body surface, the body heat carried in the bloodstream is transferred between the skin and the heat insulating material due to the resistance value and temperature difference between the heat flow. Because heat is conducted and dissipated into the atmosphere, if you use an insulating material with a known resistance to heat flow and measure the temperature of the skin-contacting surface and the air-contacting surface of this insulating material, the thermal characteristics of the skin are almost constant. ,
It is based on the fact that core body temperature can be measured non-invasively. The principle of six determination will be explained in detail below.

First, considering an infinitely expanding flat skin and a heat insulating material covering it, Figure 5 shows a simple model showing the cross section of the skin and the heat insulating material. The thick line in the figure shows the temperature distribution, and the area (n), (
The decrease in In) is due to the ratio of resistance to heat flow between the skin and the insulation, which will be discussed below. The skin in region (n) and the heat insulating material in region (■) are considered to be isotropic, and assuming that heat conduction occurs only in the X direction perpendicular to the body surface, the following heat conduction equation holds true.

However, T: temperature t: time CL t Ca: specific heat ρt of the skin and insulation material, ρ,: density of the skin and insulation material, , ,: thermal conductivity of the skin and insulation material. Also, the boundary condition is T=T= (x= -ri,)...
...(3)'r='I'L(X=O)
-”...(4) T=T, (x=L,)
--”・(5) However, T,, T,, T,: Deep warm tissue, low temperature layer tissue surface.

atmospheric temperature , L: Low-temperature layer structure, thickness of insulation material.

Solving the heat conduction equation in steady state gives.

Next, according to Fourier's law, the heat flow rates qt, qa (qt
is the skin + C1m is the heat flow rate in the insulation material) is given by the following equation.

Qt”kt”A”(aT/ax) --・---
--(s)q,=to,・A・(&T/θX)
・−・−・−(9) Since the heat flow is continuous on the skin surface, equations (6) to (jJ) are satisfied. However, R* = L t / k t ・・
・・・・・・αυR,=L,/to,
. . Old . . 2, where R,, R, is the resistance to heat flow of the skin and insulation material.

Now, the resistance of the skin to heat flow is determined by the depth to the deep source and the thermal conductivity according to the formula αυ, and Lt is generally about 2 cm as mentioned above. Also, k is muscle and I
X 10-” (cat/cm*FB: -'C] (Edited by Hisashi Sakurai et al.: ME knowledge and equipment safety.

pp, 42-43. Nanzando, 1983), and this value is also found in the skin. Therefore, the skin's resistance to heat flow R,
is 2X10"Ccm"FB'・C/Cal].

Here, determine the thermal conductivity and thickness of the heat insulating material attached to the skin surface, that is, the resistance R1 to heat flow, and measure the body surface temperature T1 and atmospheric temperature T when wearing the core thermometer using the formula αO Therefore, the deep tissue part Tht- can be determined. Furthermore, the W and MA of this method can also be applied to objects to be measured other than living bodies.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a simple core thermometer according to the present invention. The core thermometer 4 includes a heat insulating material 1 in contact with the skin 5 of the measurement site;
A temperature sensor for measuring body surface temperature that is fixed to the center of the body surface side and the atmosphere side surface of this insulation material. 2 and temperature sensor for measuring outside temperature? Consists of 3. As the temperature sensor 2 or 3, a variable resistance temperature sensor such as a thermistor or a platinum resistance temperature sensor, or a thermocouple is used.

Next, the material of the insulation material 1 can be any material according to the formula αO, but if the thermal conductivity of the insulation material is within two digits compared to the thermal conductivity of the skin, the insulation material is This is unfavorable in terms of the thickness of the material and the measurement error of the temperature sensor. Here, the thickness of the core thermometer is 1c! A heat insulating material with a thermal conductivity of about 1/2 that of the skin was used so that the body surface temperature T was an intermediate value between the deep temperature T- and the outside air temperature T1. That is, celluloid (0.50 X I at 30C
O-" cat/cm ・9 [% knee C), polyethylene/(27c 0.5 a Xl 0-' Ca L 7
cm ・n @ C), silicone rubber (0.
48X10-"cat/cnaF13"=・c) was used. If these have a thickness of about 1 cTn, the resistance R, to heat flow is 2 x 10'(cm"・"liK
・C/Ca1J, which is the same as that of the skin. As mentioned above, the heat insulating material can be made of other materials and have different thicknesses. Furthermore, according to this method, it is possible to measure the core temperature without selecting the resistance of the insulation material such that the body surface temperature T when wearing the core thermometer is an intermediate value between the core temperature T- and the outside temperature T. be. Note that unless the plane shape of the core thermometer is larger than a certain level, it will be affected by the environmental temperature and the value obtained by the temperature sensor 2 will not be as theoretical. Specifically, as long as it has a diameter of 3, it can be easily attached to any part using double-sided tape for phonocardiographs (for example, Tsukuda Miko). However, it is not limited to a circular shape, and may have other shapes.

FIG. 2 shows an embodiment of the temperature measurement circuit. The circuit includes a bridge circuit 11 that includes a temperature sensor for measuring body surface temperature, an amplifier circuit 12 that amplifies the output voltage of the bridge circuit in proportion to the body surface temperature, a bridge circuit 13 that includes a temperature sensor for measuring outside temperature, and the bridge. an amplifier circuit 14 that amplifies the output voltage of the circuit 13 in proportion to the outside temperature; and the two amplifier circuits 1.
A subtraction circuit 15 that takes an output difference of 2°14;
a multiplier circuit 16 that multiplies the output of the expression αQ by (Rs +R-)/R1, an adder circuit 17 that adds the output of the multiplier circuit 16 and the output of the amplifier circuit 14 that outputs the outside air temperature, and the output of the adder circuit 17. It consists of an A/D converter 18 that converts the temperature into a digital signal, and a digital temperature display section 19 that displays the output of the A/D converter 18. Note that an analog display section may be used for display instead of the A/D converter 18 and the digital temperature display section 19.

A bridge circuit 11 or 13 used in the device of FIG. 2 is shown in FIG. The bridge circuit has a temperature of 21 and a resistance of 2.
Consists of 2.23. The resistor 23 is for linearizing the characteristics of the temperature sensor 21, and is effective in the case of a thermistor. The unbalanced voltage of the bridge is input to the amplifier circuit 12 or 14 of FIG.

〔Effect of the invention〕

According to the present invention, a value close to the core body temperature can be measured regardless of the change K in the outside temperature, without using the heat flow compensation method. Therefore, unlike conventional core thermometers, there is no need to supply power to the heater, allowing for long-term portable monitoring of core body temperature and peripheral blood circulation, and safe temperature measurement without the risk of inflammation caused by overheating due to failure of the heater control circuit. can. Additionally, if you wear it for a long period of time, the temperature gradient on your skin will always be in a steady state, so you can measure your temperature instantly when you want to. Furthermore, since a fail-safe φ system against overheating is not required, it is highly economical.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a core body thermometer using a non-heat flow compensation method, which is an embodiment of the present invention, Fig. 2 is a core body temperature measurement circuit, which is an embodiment of the invention, Fig. 3 is a bridge circuit, and Fig. 4 is a cross-sectional view of a core thermometer using the conventional heat flow compensation method, and FIG. 5 is a simple cross-sectional model showing the temperature gradient between the skin and the insulation material. 1... Insulating material, 2... Temperature sensor for measuring body surface temperature, 3... Temperature sensor for measuring outside temperature, 4... Core thermometer, 5... Skin, 11.13... Bridge circuit, 1
2゜14...Amplification circuit, 15...Subtraction circuit, 16.
... Multiplication circuit, 17 ... Addition circuit, 18 ... A/D
Transducer, 19 Fig. 1

Claims (1)

[Scope of Claims] 1. A heat insulating material having a relatively low thermal conductivity that contacts the surface of the living body to be measured, a temperature sensor disposed at the center of the contact surface of the heat insulating material to the living body, and the heat insulating material having a relatively low thermal conductivity; A simple deep body thermometer comprising a temperature sensor disposed at the center of an air contact surface facing the contact surface of the material. 2. The simple deep body thermometer according to claim 1, wherein a variable resistance temperature sensor such as a thermistor or a platinum resistance thermometer, or a thermocouple is used as the temperature sensor. 3. Claim 1, characterized in that celluloid, polyethylene, or silicone rubber is used as the heat insulating material.
The simple core thermometer described in Items 1 to 2.