Physiological Response to Cold Exposure in Men: A Disabled Submarine Study

摘要

A disabled submarine (DISSUB) lacking power and/or environmental control will become cold, and the ambient air may become hypercapuic and hypoxic. This study examined if the combination of hypoxia, hypercapnia, and cold exposure would adversely affect thermoregulatory responses to acute cold exposure in survivors awaiting rescue. Seven male submariners (33 plus or minus 6 yrs) completed a series of cold-air tests (CAT) that consisted of 20-min at T(air) = 22 degree C, followed by a linear decline( 1 degree C.min(- 1)) in T(air) to l2 degree C, which was then held constant for an additional 150-min. CAT were performed under normoxic, normocapnic conditions (D0), acute hypoxia (D1, 16.75% 02), after 4 days of chronic hypoxia, hypercapnia and cold (D5, l6.75% O2, 2.5% CO2, 4 degree C), and hypoxia-only again (D8, l6.75% O2). The change in T(sk) during CAT was larger (P<0.05) on D0 (-5.2 degree C), vs D1 (-4.8 degree C), D5 (-4.5 degree C), and D8 (-4.4 degree C). The change (relative to 0-min) in metabolic heat production (change M) at 20-min of CAT was lower (P<0.05) on D1, D5, and D8, vs. D0, with no differences between D1, D5 and D8. Change M was not different among trial at any time point after 20- min. The mean body temperature threshold for the onset of shivering was lower on D1 (35.O8 degree C), D5 (34.85 degree C). and D8 (34.69 degree C), compared to D0 (36.01 degree C). Changes in heat storage did not differ among trials and rectal temperature was not different in D0 vs. D1, D5, and D8. Thus, mild hypoxia (l6.75% F1CO2) impairs vascolostrictor and initial shivering responses, but the additimi of elevated F1CO2 and cold had no further effect. These thermoregulatory effector changes do not increase the risk for hypothermia in DISSUP survivors who are adequately clothed.