With increasing activities in Arctic and Antarctic waters for scientific and commercial purposes, it is becoming ever more important to reduce the risks associated with diving in extreme environments. This has been the focus of a recently completed PhD thesis at the Department of Circulation and Medical Imaging (ISB) at NTNU.
Michael Lang has investigated the physiological effects of diving in extreme environments and has reviewed the underwater performance of some of the equipment necessary to make such dives as safe as possible.
“Polar diving under ice, for example, is scientifically and politically interesting, yet presents a set of physiological, equipment, training and operational challenges,” he says.
Lang, who was associated with the Smithsonian Scientific Diving Program and the National Science Foundation Antarctic Program in the USA, has looked at the use of enriched-air nitrox, the use of dive computers, ice-diving regulators and thermal protection of the divers.
In his study of the use of enriched-air nitrox as a compressed-gas breathing medium under pressure, Lang found that in certain depth ranges a higher fraction of oxygen (although not exceeding a PO2 of 1.6 ATA) and a lower fraction of nitrogen resulted in extended bottom times and a more efficient decompression. Furthermore, the use of nitrox was deemed to be at least as safe as compressed air.
Decompression status in extreme-environment diving can now be monitored efficiently through the use of dive computers. Lang found that dive computers are especially useful for multi-level, multi-day repetitive diving or decompression diving.
“Some dive computers also enable consideration of cold [temperatures] as a decompression stress risk factor, and their functions of ascent rate monitoring, real-time computation of nitrogen balances, air consumption monitoring and profile downloading capability form a solid, reliable basis for diminishing the probability of decompression sickness,” Lang explains.
One part of diving equipment that sees extra strain in cold environments is the regulator. Special regulators have been devised for ice-diving, but some nevertheless freeze up. Lang expected performance to be brand specific and the findings confirmed that some had lower failure rates than others, but even the best of regulators can freeze up or fail under polar conditions.
Another factor for extending bottom times for ice diving is the use of thermal protection such as electrically heated drysuit undergarments, gloves and socks, and full face masks with dual second stage regulators and isolator valves. This is a subject of Lang’s on-going research.
This post is also available in: Norwegian Bokmål