COMMENT:Two decades ago the maximum allowable total dive time if a diver reached 30m depth would have been around 20 minutes if the dive was planned using tables, as it commonly was. This dive profile may even have been permitted using multilevel planning techniques, but today modern dive computers do the work for us and such a profile is considered a "normal dive". The risk of decompression sickness is thought to be low among recreational divers because the majority of dives come nowhere near the no-decompression limits. After two previous days of repetitive diving, this diver suffered an injury which was diagnosed as a serious case of decompression sickness, probably without violating the dive computer's limits. That the diver made a safety stop was prudent, but of particular note is that there was oxygen onboard the boat, and the diver continued breathing oxygen on the way to the ER. After multiple hyperbaric treatments the diver is 99% recovered, which is good news, though it should be pointed out that bilateral symptoms affecting all four limbs are not typical of decompression sickness. Regardless, this case serves as a reminder that our dive computer may well keep recalculating our allowable limits but that does not mean we should dive to those limits. If 100,000 divers dive to the limits then, even though they did not "break the rules", by probability alone some will get the bends.
~ Peter Buzzacott, MPH, PhD