A Method to Determine Human Skin Heat Capacity Using a Non-Invasive Calorimetric Sensor

Callicó

et al. 2021

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A non-invasive sensor equipped with a programmable thermostat has been developed to assess in vivo the heat flow transmitted by conduction from human skin to the sensor thermostat. This device enables the assessment of the thermal properties of a 2 × 2 cm2 skin surface with a thermal penetration depth of 3–4 mm. In this work, we report the thermal magnitudes recorded with this sensor in 6 different areas (temple, hand, abdomen, thigh, wrist and heel) of 6 healthy subjects of different genders and ages, which were measured under resting conditions. Heat flow and equivalent thermal resistance are proportionally related to each other and are highly variable in magnitude and different for each zone. The heat capacity is also different for each zone. The heat flow values varied from 362 ± 17 mW at the temple to 36 ± 12 mW at the heel for the same subject, when the sensor thermostat was set at 26 °C. The equivalent thermal resistance ranged from 23 ± 2 K W−1 in the volar area of the wrist to 52 ± 4 KW−1 in the inner thigh area. The heat capacity varies from 4.8 ± 0.4 J K−1 in the heel to 6.4 ± 0.2 J K−1 in the abdomen. These magnitudes were also assessed over a 2 × 1 cm2 second-degree burn scar in the volar area of the wrist. The scar area had 27.6 and 11.6% lower heat capacity and equivalent thermal resistance, respectively, allowing an increased heat flow in the injured area. This work is a preliminary study of the measurement capacity of this new instrument.

Section: Heat Capacity Discussion (C 1 )mentioning

confidence: 99%

Section: Experimental Systemmentioning

confidence: 99%

Section: Sensor Modelmentioning

confidence: 99%

Section: Device Operationmentioning

confidence: 99%

Section: The Heat Flowmentioning

confidence: 99%

See 3 more Smart Citations

Heat flow, heat capacity and thermal resistance of localized surfaces of the human body using a new calorimetric sensor

Callicó

et al. 2021

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Advantages of in vivo measurement of human skin thermal conductance using a calorimetric sensor

Calbet

et al. 2022

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Thermal conductivity of the skin has been measured by in vivo procedures since the 1950s. These devices usually consist of temperature sensors and heating elements. In vivo measurement of skin thermal conductivity entails several difficulties. It is necessary to adequately characterize the excitation produced by the measurement. In addition, the thermal penetration depth of each instrument is different. These factors have led to the development of a multitude of techniques to measure the thermal conductivity or related magnitudes such as thermal conductance. In our case, we have built a calorimetric sensor designed to measure this magnitude directly and non-invasively. The device implements the basic principles of calorimetry and is capable of characterizing the thermal magnitudes of a 2 × 2 (4) cm2 skin region. The sensor consists of a measuring thermopile with a thermostat cooled by Peltier effect. Several skin measurements performed under different conditions resulted in a thermal conductance ranging from 0.017 to 0.050 WK−1. This magnitude, measured in vivo, is different in each studied area and depends on several factors, such as physical activity and the physiological state of the subject. This new sensor is a useful tool for studying the human body thermoregulatory response.

In vivo measurement of skin heat capacity: advantages of the scanning calorimetric sensor

2022

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Measurement of the heat capacity of human tissues is mainly performed by differential scanning calorimetry. In vivo measurement of this property is an underexplored field. There are few instruments capable of measuring skin heat capacity in vivo. In this work, we present a sensor developed to determine the heat capacity of a 4 cm2 skin area. The sensor consists of a thermopile equipped with a programmable thermostat. The principle of operation consists of a linear variation of the temperature of the sensor thermostat, while the device is applied to the skin. To relate the heat capacity of the skin with the signals provided by the sensor, a two-body RC model is considered. The heat capacity of skin varies between 4.1 and 6.6 JK−1 for a 2 × 2 cm2 area. This magnitude is different in each zone and depends on several factors. The most determining factor is the water content of the tissue. This sensor can be a versatile and useful tool in the field of physiology.