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Changing Attitudes to Deep Air September 13, 2012

Posted by Chris Sullivan in Technical Diving.
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Some day I’ll get trimix certified. I’ll probably try it out before I do so (if that’s shocking remember that someone had to be the first to try recreational trimix, and they certainly weren’t certified for it). When diving the Jodrey recently we discussed using normoxic trimix instead of air. We didn’t end up doing it, partly because not everyone could reasonably put up the money for a $150 fill. Still, as the owner of Dive Tech said, “it’s like diving two different wrecks” and as I push to greater depths I’m starting to cross what is a very fuzzy line between what is reasonable and what is not. Perhaps I’m already past it. I think that the narco stop concept has reduced some of the risks, but I still know that my reactions are slowed by the onset of narcosis.

I came across an abstract of a paper in the Rubicon Foundation archive a couple of days ago and I thought I’d repost it here. It has the catchy title: CLINICAL EVALUATION OF REPETITIVE DEEP DIVING BY RECREATIONAL DIVERS ON THE WRECK OF THE ANDREA DORIA. It seems to say that the divers in the study were just fine diving air at greater than 200′. The emphasis on the comment about narcosis is mine.

Ten male recreational divers were clinically evaluated over a 3 day period as they made repetitive deep dives [> 200 fsw) with compressed air to the wreck of the Andrea Doria in the North Atlantic Ocean. Diving profiles were recorded and verified while divers were followed clinically for signs/symptoms of decompression sickness, air embolism, and/or other diving maladies. Ultrasonic Doppler testing was used to assist in objective analysis. The divers ranged in age from 27 to 47 years old, weight from 145 to 285 lbs., previous logged dives from 50 to 1250, and diving depth from 187 to 240 fsw. During the 3 day study period the ten divers performed a total of 49 dives. None of the divers exhibited any signs/symptoms of decompression sickness or air embolism. Intravascular bubbling was detected in only 2 divers and only one diver attained a Spencer rating of 2 on any dives. The incidence of positive Doppler testing was 4.3%. Nitrogen narcosis was not a significant problem for any diver. The equipment used by each diver was extensive and included multiple back-up devices and systems. Eight divers carried at least 1 dive computer, while 1 carried 3 (in case the other 2 failed). With the water temperature at depth of 46 degrees F., all divers wore drysuits, except 1. All the divers had trained for these deep dives by performing progressively deeper dives [ > 130 fsw] several weeks to months prior to attempting these truly deep dives. Although not recommended for the average diver, repetitive deep diving by experienced recreational divers, with appropriate equipment and training, led to no incidence of decompression sickness, air embolism, or other diving maladies during this study.
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