Dear Readers
This is a much-discussed and controversial subject. There is some laboratory data that support the principle that hot water after a cold dive is a bad idea, and it appears in the abstract below (shortened from the original).
Dr Deco :doctor:
Mekjavic IB, Kakitsuba N. Effect of peripheral temperature on the formation of venous gas bubbles. Undersea Biomed Res 1989 Sep;16(5):391-401
Temperature of the tissue affects the many components involved in the formation of tissue gas phase formation: diffusion, perfusion, and inert gas solubility. Since the effects of perfusion and inert gas solubility may be counteracting in terms of enhancing growth of gas bubbles, the optimal thermal status of divers throughout a dive remains unresolved. To elucidate the role of peripheral body temperature on gas phase formation, four subjects were exposed to a 10 degree and 40 degree C environment for 3 h on two separate occasions, after a no-stop
decompression from a 12-h dive to 9.14 m (30 fsw) on air. Gas bubbles in the venous return were monitored with a Doppler ultrasonic transducer
Venous bubbles were only detected in 1 subject following the warm air exposure, whereas 3 of the 4 subjects developed Doppler-detectable bubbles during the cold air exposure. Although both the cold and warm air exposures (3 h post decompression) were uneventful, a hot shower taken by the subjects on completion of the cold air exposure (6 h post decompression) precipitated mild type I symptoms of decompression sickness. These symptoms were not present after a hot shower following the warm air exposure.
The present results indicate that despite the assumed greater inert gas solubility of tissues expected during cold air
exposure, the decrease in the perfusion may have played a more significant role in the observed levels of detectable venous gas bubbles. Development of type I symptoms following a 12-h saturation, a 3-h cold exposure, and a subsequent hot
shower suggests that a rapid rise in peripheral temperature may cause a significant rise in tissue gas tension. This increase in tension does not seem to be sufficiently reduced by increased perfusion to the tissues to prevent bubble formation.