PubMed · 4485212
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M Maeda. 1972. [Heat conduction].. https://pubmed.ncbi.nlm.nih.gov/4485212/
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The present study was conducted to measure nasal mucosal blood flow (NMBF) during body warming. Five subjects [mean (SD) 24 (2) years], wearing only shorts and a thick felt hat with ear flaps, were immersed to the neck in a bath at 40 (0.5) degrees C. Tympanic (Tty), esophageal (Tes), mean unweighted skin (Tsk), nose skin and ear pinna skin were recorded at 1-min intervals. NMBF on the lower septal wall was estimated using a laser Doppler flow meter. At rest Tty and Tes were both 36.5 degrees C. Tty dropped significantly below Tes during body warming, despite impeded heat loss from the head due to the felt hat. Tty increased to 37.3 degrees C and Tes increased to 37.5 degrees C during the immersion. During the immersion all skin temperatures were steady or increasing, ruling out the possibility of a contamination of Tty from Tsk. Body warming significantly (P = 0.001) increased NMBF by approximately three times from resting values at the end of immersion. During the period of increasing core temperatures NMBF was significantly correlated to Tty (r = 0.93, P = 0.0001) and Tes (r = 0.97, P = 0.0001), suggesting the blood flow change in this tissue was a thermoregulatory response. The increased NMBF during hyperthermia supports the hypothesis of respiratory cooling involvement in selective brain cooling of humans.
The wind chill index (WCI) and the more widely used wind chill equivalent temperature represent an attempt to combine several weather-related variables (temperature, wind velocity and solar radiation) into a single index which can indicate human comfort. Since its introduction in 1945, the WCI has been criticized mainly on the ground that the underlying model does not comply with modern heat transfer theory. In spite of that, the WCI, "calibrated" to human comfort, has proven to be successful in predicting discomfort and tolerance of man to the cold. Nevertheless, neither the WCI nor the wind chill equivalent temperature can be actually measured and, therefore, without the additional 'calibration' they are meaningless. In this study we have shown that the WCI represents the instantaneous rate of heat loss from bare skin at the moment of exposure to the cold, and as such, it correlates reasonably well with measurable variables that represent a feeling of cold. Two new wind chill indicators have been introduced: exposed skin temperature and maximum exposure time. These indicators yield more information than the WCI provides, are measurable, have physical meaning and are based on established heat transfer principles.