title: User settings on dive computers: reliability in aiding conservative diving.
abstract: BACKGROUND
  Divers can make adjustments to diving computers when they may need or want to dive more conservatively (e.g., diving with a persistent (patent) foramen ovale). Information describing the effects of these alterations or how they compare to other methods, such as using enriched air nitrox (EANx) with air dive planning tools, is lacking.
  
  
  METHODS
  Seven models of dive computer from four manufacturers (Mares, Suunto, Oceanic and UWATEC) were subjected to single square-wave compression profiles (maximum depth: 20 or 40 metres' sea water, msw), single multi-level profiles (maximum depth: 30 msw; stops at 15 and 6 msw), and multi-dive series (two dives to 30 msw followed by one to 20 msw). Adjustable settings were employed for each dive profile; some modified profiles were compared against stand-alone use of EANx.
  
  
  RESULTS
  Dives were shorter or indicated longer decompression obligations when conservative settings were applied. However, some computers in default settings produced more conservative dives than others that had been modified. Some computer-generated penalties were greater than when using EANx alone, particularly at partial pressures of oxygen (PO₂) below 1.40 bar. Some computers 'locked out' during the multi-dive series; others would continue to support decompression with, in some cases, automatically-reduced levels of conservatism. Changing reduced gradient bubble model values on Suunto computers produced few differences.
  
  
  CONCLUSIONS
  The range of possible adjustments and the non-standard computer response to them complicates the ability to provide accurate guidance to divers wanting to dive more conservatively. The use of EANx alone may not always generate satisfactory levels of conservatism.
authors.affiliation: UK National Facility for Scientific Diving hosted at the Scottish Association for Marine Science Laboratories, Scottish Association for Marine Science, Dunstaffnage Marine Laboratories, Dunbeg, Oban, Argyll PA37 1QA, Scotland, mdjs@sams.ac.uk.|West Scotland Centre for Diving and Hyperbaric Medicine, Scottish Association for Marine Science.
authors.forename: Martin D J
authors.initials: MD
authors.lastname: Sayer
authors.affiliation: UK National Facility for Scientific Diving hosted at the Scottish Association for Marine Science Laboratories, Dunbeg, Oban, Argyll, Scotland.|West Scotland Centre for Diving and Hyperbaric Medicine, Scottish Association for Marine Science.
authors.forename: Elaine
authors.initials: E
authors.lastname: Azzopardi
authors.affiliation: Chalmers University of Technology, Gothenburg, Sweden.|SeaBear Diving Technology, Austria (now part of Johnson Outdoors).
authors.forename: Arne
authors.initials: A
authors.lastname: Sieber
mesh_terms: D001274:Atmospheric Pressure; D003201:Computers / Q000145:classification / Q000592:standards*; D003664:Decompression / Q000592:standards*; D004242:Diving / Q000592:standards*; D006801:Humans; D012016:Reference Values; D015203:Reproducibility of Results; D012623:Seawater
keywords: Computers - diving; altitude; decompression; enriched air – nitrox; persistent (patent) foramen ovale (PFO); review article; safety