Journal Article

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Diving and hyperbaric medicine

Diving.Hyperb.Med.

Sep

44

3

124

136

LR: 20160128; JID: 101282742; EIN: Diving Hyperb Med. 2015 Dec;45(4):270. PMID: 26687317; OTO: NOTNLM; 2014/02/09 [received]; 2014/07/01 [accepted]; ppublish

Australia

1833-3516; 1833-3516

PMID: 25311318

eng

Journal Article; Observational Study; Research Support, Non-U.S. Gov't; Validation Studies; IM

Unknown(0)

25311318

INTRODUCTION: Tasmania's aquaculture industry produces over 40,000 tonnes of fish annually, valued at over AUD500M. Aquaculture divers perform repetitive, short-duration bounce dives in fish pens to depths up to 21 metres' sea water (msw). Past high levels of decompression illness (DCI) may have resulted from these 'yo-yo' dives. This study aimed to assess working divers, using Doppler ultrasonic bubble detection, to determine if yo-yo diving was a risk factor for DCI, determine dive profiles with acceptable risk and investigate productivity improvement. METHODS: Field data were collected from working divers during bounce diving at marine farms near Hobart, Australia. Ascent rates were less than 18 m.min(-)(1), with routine safety stops (3 min at 3 msw) during the final ascent. The Kisman-Masurel method was used to grade bubbling post dive as a means of assessing decompression stress. In accordance with Defence Research and Development Canada Toronto practice, dives were rejected as excessive risk if more than 50% of scores were over Grade 2. RESULTS: From 2002 to 2008, Doppler data were collected from 150 bounce-dive series (55 divers, 1,110 bounces). Three series of bounce profiles, characterized by in-water times, were validated: 13-15 msw, 10 bounces inside 75 min; 16-18 msw, six bounces inside 50 min; and 19-21 msw, four bounces inside 35 min. All had median bubble grades of 0. Further evaluation validated two successive series of bounces. Bubble grades were consistent with low-stress dive profiles. Bubble grades did not correlate with the number of bounces, but did correlate with ascent rate and in-water time. CONCLUSIONS: These data suggest bounce diving was not a major factor causing DCI in Tasmanian aquaculture divers. Analysis of field data has improved industry productivity by increasing the permissible number of bounces, compared to earlier empirically-derived tables, without compromising safety. The recommended Tasmanian Bounce Diving Tables provide guidance for bounce diving to a depth of 21 msw, and two successive bounce dive series in a day's diving.

Smart,D.R., Van den Broek,C., Nishi,R., Cooper,P.D., Eastman,D.

Faculty of Heath Sciences, University of Tasmania, Department of Diving and Hyperbaric Medicine Royal Hobart Hospital Hobart, Tasmania 7000, Australia, Phone: +61-(03)-6222-8193, Fax: +61-(03)-6222-7268, E-mail: david.smart@dhhs.tas.gov.au.; Department of

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2014