Respiratory Heat Loss Limits in Helium-Oxygen Saturation Diving
NAVY EXPERIMENTAL DIVING UNIT PANAMA CITY FL
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Convective respiratory heat transfer in divers breathing cold helium- oxygen is a major avenue of body heat loss for which there is no effective thermoregulatory compensation. Review of recent studies of hyperbaric respiratory heat loss provides a physiological data base for updating current minimum inspired gas temperatures for saturation diving. The new proposed inspired gas temperature-depth curve is based upon a maximum convective respiratory heat loss of 20 Wsq m for a resting diver maintaining thermoneutral skin temperature in a hot water suit. This level of respiratory heat loss is predicted to allow an average rectal temperature drop of 0.25 C per hour, and will support a four hour mission. The new limits are designed to allow divers with any ventilatory response to exercise or cold to gain heat from exercise, although it is expected that most of the exercise heat remaining after obligatory increases in respiratory heat loss from the ventilatory response to the exercise, will be dissipated through the divers skin as he adjusts his hot water flow and temperature for comfort.
- Stress Physiology
- Life Support Systems