New neurophysiological human thermal model based on thermoreceptor responses.

A new neurophysiological human thermal model based on thermoreceptor responses, the NHTM model, has been developed to predict regulatory responses and physiological variables in asymmetric transient environments. The passive system is based on Wissler's model, which is more complex and refined. Wissler's model segments the human body into 21 cylindrical parts. Each part is divided into 21 layers, 15 for the tissues and 6 for clothes, and each layer is divided into 12 angular sectors. Thus, we have 3780 nodes for the tissues and 1512 for clothes. The passive system simulates heat exchange within the body and between the body and the surroundings. The active system is composed of the thermoregulatory mechanisms, i.e., skin blood flow, shivering thermogenesis, and sweating. The skin blood flow model and the shivering model are based on thermoreceptor responses. The sweating model is that of Fiala et al. and is based on error signals. The NHTM model was compared with Wissler's model, and the results showed that a calculation based on neurophysiology can improve the performance of the thermoregulation model. The NHTM model was more accurate in the prediction of mean skin temperature, with a mean absolute error of 0.27 °C versus 0.80 °C for the original Wissler model. The prediction accuracy of the NHTM model for local skin temperatures and core temperature could be improved via an optimization method to prove the ability of the new thermoregulation model to fit with the physiological characteristics of different populations.

Infrared imaging analysis for thermal comfort assessment.

Skin temperature is a relevant and effective indicator for objective evaluation of human sensations and thermal states according to the surrounding thermal stresses. Managed by skin blood flow, sympathetic nervous system (constriction and sweating), subcutaneous thermal structure and facial vein patterns, facial coetaneous temperature variability can give information non-invasively on many physiological functions. These informations are deduced from thermal images obtained by far infrared imaging (7 - 14 microm). The work presented here deals with facial thermographic image analysis. Thermal regions of interest are extracted, such as left and right front, left and right cheek, left and right periobital region. Each region is analyzed by the FFT power spectrum calculation regarding to specific spectral band.

Wearable medical devices using textile and flexible technologies for ambulatory monitoring.

Health smart clothes are in contact with almost all the surface of the skin offer large possibilities for the location of sensors for non invasive measurements. Head band, collar, tee-shirt, socks, shoes, belts for chest, arm, wrist, legs ... provide localization with specific purpose taking into account their proximity of an organ or a source of biosignal, and also its ergonomic possibility (user friendly) to fix a sensor, and the associated instrumentations (batteries, amplifiers, signal processing, telecom, alarm, display ...). Progress in science and technology offers, for the first time, intelligence, speed, miniaturization, sophistication and new materials at low cost. In this new landscape, microtechnologies, information technologies and telecommunications are a key factor. Microsensors : Microtechnologies offer the possibility of small size, but also intelligent, active device, working with low energy, wireless and non invasive or mini invasive. These sensors have to be thin, flexible and compatible with textile, or made using textile technologies, new fibers with specific properties: mechanical, electrical, optical ... The field of applications is very large, e.g. continuous monitoring on elderly population, professional and military activities, athlete's performance and condition, and people with disabilities. The research are oriented toward two complementary directions: Improving the relevancy of each sensor and increasing the number of sensors for having a more global synthetic and robust information.