Posted by MHK on October 26, 2004 at 14:36:37:
In Reply to: What are some of the dangers? posted by Elaine on October 26, 2004 at 07:52:22:
Capt. Tim asked me to comment on this thread as it is not my common habit to post to this list, but I guess I've recovered enough of Tim's anchor's so he asked me to pitch in ;-). In reviewing this thread it's seems likely that most of the responses so far have missed the possible cause for this fatality, which is to say that when attempting to free an anchor this mission normally involves a fair amount of work, especially if the anchor is heavy. That being said, I wouldn't be surprised at all if this diver had a buildup of C02. Any number of contributing factors can enter into the equation but briefly C02 is 130 times more narcotic then Nitrogen and as a secondary side effect has the ability of making the diver feel that s/he has a shortness of breath (Dypsnea), when that happens the diver tends to breath more rapidly, as a result of the more rapid breaths the diver retains more C02, which again is 130 more narcotic, and the cycle repeats itself over and over wherein every breath isn't a full exchange so the diver continually retains the C02 and at some point is so narced that any decision is significantly impacted because of the extreme narcosis. Dr. Peter Bennet formely of DAN coined the term for this as the "vicious cycle".
Depending on the depth the obvious things to concern yourself with is gas density, the deeper you are on an air based mix, the denser the gas thus the more difficult to breath. Proposed solution Nitrox or Triox.
Streamlined equipment configuration will help reduce drag and will reduce the potential for C02 build up.
Regulator performance, obviously the easy the reg is to breath from the less chance of retaining C02.
Workload, obviously recovering or freeing an anchor involves physical excursion, whenever I recover an anchor I make a habit of frequently stopping what I'm doing simply to avoid retaining C02. Take a few deep breathes and ensure a full exchange and then go back to the task at hand..
Team. Don't attempt this solo. Work in a unified team to reduce workload, to have a second set of eyes and a second brain to watch for obvious signs and symptoms of C02 buildup and/or Narcosis.
Have the skipper allow for enough slack in case the chain is wrapped around the rock(s)..
And lastly, if recovering the anchor with Terry, make sure you have back-up lights, a helmet and a first aid kit on deck ;-)
Anyway, hope that helps but feel free to PM me if you have any questions.
Later