Dive profile risks and conservatism
Photo credit: www.sditdi.com
Our ability to dive and extend dive times over the years has improved greatly thanks to improved technologies and knowledge. However, we need to consider conservatism in our diving practices to reduce the risk of decompression sickness (DCS).
The recent death of Dr Garman (see our previous articles FATAL TECHNICAL DIVING ACCIDENT ON WORLD RECORD ATTEMPT and DR GARMAN’S BODY FOUND AFTER FATAL DIVING ACCIDENT), attracted a lot of very good post-incident analysis but not a lot of practical guidance on how to avoid making the same mistakes.
An article by Dr Pollock presents conceptual and practical steps to improve dive safety.
Conceptual control can be achieved by adhering to these principles:
- 1) Know the risks,
- 2) Take responsibility for your own safety,
- 3) Understand the tools you are using (eg what is your dive computer actually doing),
- 4) Evaluate information critically (instead of following guides, computers and gauges blindly),
- 5) Know your risk tolerance,
- 6) Maintain a safety oriented mental state,
- 7) Reinforce safety messaging,
- 8) Avoid mission creep (this means maintaining discipline and not eroding your safety margin to go just that little bit further),
- 9) Pick your partners well,
- 10) Use tools to defend your practice (use your dive computer to the conservative settings that work for you).
Practical strategies for implementation include:
- 1) Use of multilevel profiles on appropriate dive sites, to reduce decompression stress gradually and to avoid the temptation to go to the extremes of your training as is often the case with square profiles.
- 2) Don’t fixate on rules at the expense of safety, for example the commonly taught rule of always returning to the surface with 50 bar, when mindlessly applied is counterproductive. Throwing in our own two cents, this is a particularly terrible rule, there is no virtue in returning to the surface with your reserve intact if you have had to skip a safety stop to achieve it – making sure you have enough gas to exit the water safely is the whole point of having the reserve in the first place.
- 3) It makes sense to plan your deepest dive first, but the rule against reverse profiles is obsolete, there is no practical reason why the first dive MUST be deeper than the second dive. In particular, do not mindlessly fixate on such rules to push the first dive to an unnecessary depth merely to avoid a reverse profile (noting that reverse profiles are actually fine).
- 4) Surface intervals are a minimum, more time off-gassing on the surface reduces the severity of your next dive.
- 5) No-fly times are a minimum, and 24 hours is a better rule of thumb.
Building conservatism into both yours and your buddy’s diving will help reduce the risks associated with diving. Planning and thoughtfulness during a dive can lead to a net effect of a high level of safety, often with relatively little compromise to your diving experience.
The original article ‘Defensive Dive Profile Planning’ by Neil W Pollock, PhD. is available here.