Immersion hypothermia: comparative protection of anti-exposure garments in calm versus rough seas.

To evaluate the thermal performance of anti-exposure garments in rough seas, eight garment-ensembles were studied: 7 foam-insulated garments (2 tight-fitting "wet" suits, 3 loose-fitting "wet" garments, 2 "dry" suits) and 1 uninsulated, loose-fitting control. Mean calm and rough water temperatures were 10.7 and 11.1 degrees C, respectively. Rectal temperature, back skin temperature, heart rate, and subjective evaluations of garment protection were measured. Loose-fitting, "wet" garments allowed significantly greater (approximately 50-100%) mean rectal temperature cooling rates and significantly larger declines in skin temperature in rough water than in calm water. Such differences were not found for either the tight-fitting "wet" suits or the "dry" suits. Heart rates were significantly higher in rough seas than in calm seas for all garments. Rectal and skin temperature changes were positively correlated with each other and with subjective evaluation of cold water flushing; they were negatively correlated with warmth and tightness-of-fit. "Dry" garments provided better protection than did "wet" garments in both sea conditions, and tight-fitting "wet" garments provided better protection than did loose-fitting "wet" garments in rough but not in calm seas. Accidental immersion in rough seas may be associated with significantly lower survival times than previously estimated from calm-water studies.