Contribution of Electrophysiological Signals in the Study of Thermal Comfort: a Case Study

Thermal comfort is defined as a mental condition that expresses satisfaction with thermal environments, therefore being subjectively assessed by the individual. Nonetheless, thermal comfort (or discomfort) causes a physiological response that may be translated objectively by electrophysiological signals. Additionally, the sensation of thermal comfort also depends on ambient conditions, such as air temperature and relative humidity, which can be easily quantified. In this way, the present study aimed to assess the physiological response in different thermal comfort environments by collecting and analyzing objective parameters of electrical brain and cardiac activities, as well as thermal comfort parameters. Herein, we enrolled five healthy participants, 2 females and 3 males, aged between 22 and 27 years, and with clothing insulation levels between 0.26 clo and 0.52 clo. These participants underwent a mental task whilst exposed to two different thermal environments - one considered to be warm and the other comfortable. Electroencephalography and photoplethysmography techniques were used to collect physiological data from which brainwave activity and heart rate parameters, were respectively derived, and correlated with thermal comfort indexes as computed from the measured air temperature, relative humidity and other thermal quantities. Our results seem to indicate the existence of a relationship between electrophysiological response and thermal comfort indexes, in accordance with the literature. In thermally uncomfortable environments, brain Delta (0.5-4 Hz) activity was observed to be higher, whilst the Beta (13-30 Hz) activity was lower, as well as heart rate values were in general observed to be higher and heart rate variability values lower in comparison with thermally comfortable environments. Whilst these results were promising, further research should be performed to validate our findings, including a larger sample size and more variate thermal environments.