[Truncated abstract] Introduction Running out of air, loss of buoyancy control, rapid ascent and/or exceeding accepted safe depth/time limits often precede both DCI and drowning. This study investigates who is most likely to experience these conditions and explores potential risk factors among certified recreational divers joining organised scuba dives in Western Australia (WA). Methods Dive and diver details were recorded and depth/time loggers were attached to participating divers. Four dive problems were defined: dives ending with less than 50-bar remaining in the cylinder, those with a reported buoyancy problem, those with an ascent recorded faster than 18m/min, or dives resulting in tissue pressure estimates greater than Mvalues recommended by Diving Science and Technology (DSAT). These cases were compared with control dives made at the same dive site at the same time, by divers who did not report or record these conditions. The data were stratified by dive number and a conditional logistic regression model identified which factors were significantly associated with each of the four conditions. Results The opportunity to participate was presented to 503 divers joining organised group dives and 321 divers participated, suggesting an overall participation of 64%. In total 1032 organised recreational dive profiles were collected. Recorded depths ranged from one to 45m, water temperatures ranged from 15oC to 29oC and vertical visibility was to the bottom or at least 20m at the start of 792 (77%) of the dive profiles. Case dives returning with less than 50-bar (n=183) were compared with 510 control dives ending with more than 50-bar. Predictors of a dive ending with less than 50-bar were: young age, males, fewer dives in previous years, a longer recent break since last diving, deeper average depth, smaller cylinders, heavier breathing and the divers were 16-times more likely to report being surprised at the end of the dive by the level of their remaining gas. Sixty-eight case dives reportedly involved a buoyancy problem experienced at the same time and place as 320 control dives where divers did not report a buoyancy problem. Predictors of a buoyancy problem were being unable to describe how to check for neutral buoyancy, feeling not in control during the final ascent and recording a faster maximum ascent rate. Seventy-one dives recorded ascents faster than 18m/min and these were matched to 282 control dives with ascents slower than 18m/min. On average, case dives ascended at a maximum rate of 21.5m/min whilst the maximum ascent rate during control dives averaged 11.7m/min. Case dives were shorter and more often resulted in reports of a buoyancy problem. Thirty-eight dives recorded depth-time profiles where at least one DSAT M-value was exceeded and these were matched to 152 control dives that did not exceed an Mvalue. Case dives exceeding at least one M-value were associated with females, deeper average depth and made by divers who were less likely to have been as deep before...
|Qualification||Doctor of Philosophy|
|Publication status||Unpublished - 2010|