THERMAL STATUS OF WET-SUITED DIVERS USING CLOSED-CIRCUIT O-2 APPARATUS IN SEA-WATER OF 17-18.5-DEGREES-C

A wet suit may not provide adequate thermal protection when diving in moderately cold water (17-18 degrees C), and any resultant mild hypoth ermia may impair performance during prolonged diving. We studied heat exchange during a dive to a depth of 5 m in sea water (17-18.5 degrees C) in divers wearing a full wet suit and using closed-circuit oxygen breathing apparatus. Eight fin swimmers dived for 3.1 h and six underw ater scooter (UWS) divers propelled themselves through the water for 3 .7 h. The measurements taken throughout the dive were the oxygen press ure in the cylinder and skin and rectal temperatures (T-re). Each subj ect also completed a cold score questionnaire. The T-re decreased cont inuously in all subjects. Oxygen consumption in the fin divers (1.40 l . 1 min(-1)) was higher than that of the UWS divers (1.05 l . min(-1) ). The mean total insulation was 0.087 degrees C . m(2) . W-1 in both groups. Mean body insulation was 37% of the total insulation (suit ins ulation was 63%). The reduction in T-re over the Ist hour was related to subcutaneous fat thickness. There was a correlation between cold sc ore and T-re at the end of 1 h, but not after that. A full wet suit do es not appear to provide adequate thermal protection when diving in mo derately cold water.