Re-inventing Core Body Temperature Measurement

Abstract: Humans are considered an integral part of future energy systems. In this context, constant awareness of human body status is critical for building responsive and intelligent environment that take energy efficiency and human comfort to the highest limits. Core body temperature is one of human body vital signs for body’s proper functioning and comfortability. Continuous non-invasive Core Body Temperature (CBT) measurements is important for patient monitoring and health status tracking in sports, sleep studying and other clinical and care procedures. Currently, there is a lack of precise and versatile methods to capture core body temperature under varying ambient conditions and through practical wearable solutions. Meanwhile, greenTEG AG, Zurich Switzerland, has developed a batch production method enabling the production of small, sensitive and very robust heat flux sensors. The main aim of this project was to develop a commercial product which for the first time measured core body temperature by placement inside a light, affordable wearable hold. This report presents a comprehensive review on heat transfer in human body and thermoregulation concepts in the first chapter followed by the state of the art methods. Then in chapter 2, according to the project design, full description and result discussions of the numerical model of human body developed by the author, was used as a prelude to the experimental tests. The model developed for this study was a Finite Difference model of different tissue layers combined with appropriate convection and radiation heat loss formulations. Tests were conducted through rigorous considerations of real body conditions including variable core body temperature and changing environmental conditions. Numerical tests were also validated by comparing with experimental results. Numerical results provided a precise preview of experimental models’ measurements and were used in the development of experimental setups. One of unique aspects of this study was the fact that the numerical model was used along with the sensor output to capture CBT and was considered a part of final product. In chapter 3, experimental tests on both skin phantom and human trials are discussed together with the sensor design and configuration. Results show that our CBT monitoring system is capable of measuring stable core body temperature under changing environmental conditions. It could also track circadian rhythm of core temperature during sleep, which for the first time, makes it possible for non-invasive miniaturized CBT tracking systems to measure accurate core temperature. These calculations are based on novel algorithms by greenTEG that could compensate for varying environmental conditions.