Usefulness of R-R interval and its variability in evaluation of thermal comfort

The use of R-R interval and the coefficient of variation in R-R intervals (CVR-R) for the evaluation of thermal comfort was investigated. The experiments were carried out with ten male subjects but data from one were excluded from the analysis. Thermal sensation, comfort, and tolerance of environmental conditions were reported and mean skin temperature, R-R interval and CVR-R were monitored during a 3 h period in a climatic chamber with the operative temperature set at 26, 20, or 30 degrees C. Relative humidity was maintained at ca. 50% in each case. At the operative temperature of 20 degrees C, the mean skin temperature was significantly lower, the cold sensation was significantly more intense, and discomfort was significantly greater than at 26 degrees C and R-R interval was increased significantly. Seven of the nine subjects were unable to tolerate this thermal environment. The R-R interval and CVR-R were increased in five and four of those seven subjects, respectively. At the operative temperature of 30 degrees C, the mean skin temperature was significantly higher, and the sensation of warmth was significantly more intense than at 26 degrees C. Seven of the nine subjects felt discomfort, and four of the seven reported an inability to tolerate this thermal environment. The R-R interval and CVR-R were decreased in four and three of these four subjects, respectively. At the operative temperature of 20 degrees C CVR-R was significantly greater than that at 30 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)