[abstract] SAFE DECOMPRESSION LIMITS FOR NO-DECOMPRESSION DIVES USING THE DOPPLER ULTRANSONIC BUBBLE DETECTOR.

Abstract

Safe bottom-time limits for no-decompression dives on compressed air vary widely depending on which diving manual is used. Spencer (J. Appl. Physiol. 40(2): 229-236, 1976) has shown by using the Doppler ultrasonic bubble detector that the safe limits, compared to those of the U.S. Navy Diving Manual, are slightly less conservative in the short deep dives but more conservative in both the middle depth range and for long shallow exposures. As a great deal of diving is done with no decompression stops, it is important to know what the safe limits are. A total of 185 man-dives were conducted at depths ranging form 16.5 to 80 metres of seawater (msw) with no decompression stops in a hyperbaric chamber. The main dive series consisted of 20 dives (120 man-dives), with each dive consisting of two dry divers doing moderate upper torso work, two wet divers doing moderate to heavy upper torso work with weights, and two dry attendants doing light work tending the wet divers. The water temperature was between 5 and 8 degrees C. Rectal temperatures were obtained on the wet divers in the long exposure dives. Each subject was monitored for bubbles in the precordial region and the subclavian sites for at least two hours after surfacing with the Doppler ultrasonic bubble detector. The results show that for young, fit, and well-acclimatized divers, no-decompression dives in the moderate to deep depth range could be done for bottom times in excess of the U.S. Navy limits, although there is some element of risk at the deepest depths. The results also showed that other factors such as cold stress and pre-dive and post-dive activities must be considered.