Yesterday, we mentioned that 4 divers in the UK got bent after ascending too quickly. Granted, they were in "emergency-mode," ascending with a dive partner who was having problems (and who ultimately died). Nevertheless, I was pleased to find this article about ascending safely, in which the author claims "the greatest risk of decompression injury may occur in the last 15 feet of ascent." I think this may surprise many divers, because in the last 15 feet of the dive, the pressure on a diver (and his or her bubbles) is the least. But that's exactly the point: during the final ascent, bubbles grow fastest and, as such, we are at the greatest risk of arterial gas embolism. In fact, straining to climb the ladder onto the boat, and hefting tanks and weights on the boat, may increase our risk of both DCS and embolism. In other words: take it easy.
The article provides a number of great tips for slowing down. Personally, I know how difficult it can be to ascend slowly during the last 15 feet -- not, as the author suggests, because you want to reach the boat quickly -- but for more practical reasons: the air in your BC is expand ing rapidly, forcing you up. Consequently, after your safety stop and before you begin your final ascent, the author suggests dumping some of the air from your BC and kicking gently (if necessary) to reach the surface. Some of the other tips he provides are:
- Extend your safety stop.
- Be sure you're neutral before you leave the safety stop.
- Keep your throat open all the way up.
- Try to stop halfway.
- Take your time.
- Float on the surface five or 10 minutes.
- Take off your heavy gear in the water.
1. To go a little farther, consider that the air in your body expands by roughly 50% in that final 16.7 feet. Between 99 and 66 feet, the expansion is only 33.3%. Be careful out there, divers. We don't want anyone to blow up like that poor kid at the chocolate factory.
Posted at 2:12PM on Jul 12th 2006 by Billy Williamson