Journal of Applied Physiology, Vol 64, Issue 5 1916-1922, Copyright © 1988 by American Physiological Society
Effect of pressure on thermal insulation in humans wearing wet suits
Y. H. Park, J. Iwamoto, F. Tajima, K. Miki, Y. S. Park and K. Shiraki
Department of Physiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan.
The present work was undertaken to determine the critical water temperature
(Tcw), defined as the lowest water temperature a subject can tolerate at
rest for 3 h without shivering, of wet-suited subjects during water
immersion at different ambient pressures. Nine healthy males wearing
neoprene wet suits (5 mm thick) were subjected to immersion to the neck in
water at 1, 2, and 2.5 ATA while resting for 3 h. Continuous measurements
of esophageal (T(es)) and skin (Tsk) temperatures and heat loss from the
skin (Htissue) and wet suits (Hsuit) were recorded. Insulation of the
tissue (Itissue), wet suits (Isuit), and overall total (Itotal) were
calculated from the temperature gradient and the heat loss. The Tcw
increased curvilinearly as the pressure increased, whereas the metabolic
heat production during rest and immersion was identical over the range of
pressure tested. During the 3rd h of immersion, Tes was identical under all
atmospheric pressures; however, Tsk was significantly higher (P less than
0.05) at 2 and 2.5 ATA compared with 1 ATA. A 42 (P less than 0.001) and
50% (P less than 0.001), reduction in Isuit from the 1 ATA value was
detected at 2 and 2.5 ATA, respectively. However, overall mean Itissue was
maximal and independent of the pressure during immersion at Tcw. The Itotal
was also significantly smaller in 2 and 2.5 ATA compared with 1 ATA. The
Itissue provided most insulation in the extremities, such as the hand and
foot, and the contribution of Isuit in these body parts was relatively
small. On the other hand, Itissue of the trunk areas, such as the chest,
back, and thigh, was not high compared with the extremities, and Isuit
played a major role in the protection of heat drain from these body parts.
