title: A 10-year estimate of the incidence of decompression illness in a discrete group of recreational cave divers in Australia.
abstract: BACKGROUND
  The vast majority of freshwater cave diving in Australia occurs within the limestone caves of the Gambier karst in the south-east of South Australia. The incidence of decompression illness (DCI) in cave divers is presumed to be higher than open-water recreational divers because of the greater depths involved, but has not previously been reported. Our aim was to determine the incidence of DCI in cave divers, the patterns of diving and the outcome of hyperbaric treatment.
  
  
  METHODS
  This was a retrospective cohort study of cave divers with DCI presenting to the Royal Adelaide Hospital or The Alfred Hospital over a 10-year period between 2002 and 2012. We reviewed case notes of cave divers who were treated for DCI after diving in the Mt Gambier karst. As there are no records of the number of dives performed during the study period we generated a denominator for the incidence of DCI by extrapolating available data and making a number of assumptions about the number of dives per dive permit issued.
  
  
  RESULTS
  Sixteen patients were treated for DCI during the study period. The precipitating dive was a single deep decompression dive in seven cases, multiday repetitive dive sequences in eight and a non-decompression dive in one. Three of the 16 cases of DCI involved dives in excess of 90 metres' fresh water (mfw) using trimix. As the total estimated number of dives in the study period was approximately 57,000 the incidence of DCI in Australian cave divers was estimated to be 2.8:10,000 (0.028%). It is possible that the overall incidence of DCI is as high as 0.05%, and even higher when dives to depths greater than 90 mfw are involved.
  
  
  CONCLUSIONS
  The estimated incidence of DCS in this series is lower than expected but consistent with other series describing DCI in cold-water recreational diving.
authors.affiliation: Hyperbaric Medicine Unit, Royal Adelaide Hospital, North Terrace, Adelaide, SA 5000, Australia, Phone: +64-(0)8-8222-5116 E-mail: drharry@me.com.
authors.forename: Richard Jd
authors.initials: RJ
authors.lastname: Harris
authors.affiliation: Department of Intensive Care and Hyperbaric Medicine, The Alfred Hospital, Melbourne.
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Frawley
authors.affiliation: Department of Intensive Care and Hyperbaric Medicine, The Alfred Hospital, Melbourne.
authors.forename: Bridget C
authors.initials: BC
authors.lastname: Devaney
authors.affiliation: Department of Intensive Care and Hyperbaric Medicine, The Alfred Hospital, Melbourne.
authors.forename: Andrew
authors.initials: A
authors.lastname: Fock
authors.affiliation: Hyperbaric Medicine Unit, Royal Adelaide Hospital, North Terrace, Adelaide.
authors.forename: Andrea B
authors.initials: AB
authors.lastname: Jones
mesh_terms: D000328:Adult; D001315:Australia / Q000453:epidemiology; D059552:Caves; D003080:Cold Temperature; D003664:Decompression / Q000009:adverse effects; D003665:Decompression Sickness / Q000453:epidemiology* / Q000628:therapy; D004242:Diving / Q000009:adverse effects* / Q000706:statistics & numerical data; D005618:Fresh Water; D006801:Humans; D006931:Hyperbaric Oxygenation; D015994:Incidence; D008297:Male; D011998:Recreation; D012189:Retrospective Studies; D013997:Time Factors
keywords: Decompression illness; cave diving; clinical audit; decompression sickness; epidemiology; first aid; technical diving