title: Field validation of Tasmania's aquaculture industry bounce-diving schedules using Doppler analysis of decompression stress.
abstract: BACKGROUND
  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.
authors.affiliation: 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.
authors.forename: David R
authors.initials: DR
authors.lastname: Smart
authors.affiliation: Department of Diving and Hyperbaric Medicine, Royal Hobart Hospital, Hobart, Tasmania.
authors.forename: Cory
authors.initials: C
authors.lastname: Van den Broek
authors.affiliation: Formerly Experimental Diving Unit, Defence Research and Development Canada - Toronto.
authors.forename: Ron
authors.initials: R
authors.lastname: Nishi
authors.affiliation: Department of Diving and Hyperbaric Medicine, Royal Hobart Hospital, Hobart, Tasmania.
authors.forename: P David
authors.initials: PD
authors.lastname: Cooper
authors.affiliation: Formerly Experimental Diving Unit, Defence Research and Development Canada - Toronto.
authors.forename: David
authors.initials: D
authors.lastname: Eastman
mesh_terms: D017756:Aquaculture; D003665:Decompression Sickness / Q000000981:diagnostic imaging* / Q000209:etiology; D004242:Diving / Q000009:adverse effects* / Q000502:physiology; D004526:Efficiency; D006801:Humans; D009784:Occupational Diseases / Q000000981:diagnostic imaging* / Q000209:etiology; D011446:Prospective Studies; D012623:Seawater; D013648:Tasmania; D013997:Time Factors; D014463:Ultrasonography
keywords: Doppler; Occupational diving; decompression sickness; decompression tables; diving research; diving tables; repetitive diving; surface supply breathing apparatus (SSBA)