Posted by Melvin on August 07, 2002 at 14:36:23:
In Reply to: Dive Tables vs. Computers posted by Eagle Ray on August 07, 2002 at 10:48:39:
I agree with others. Saying that 85% of the divers that got DCI had computers is like saying that 85% of the accident victums on the highway in 2002 were driving cars (as compared to the year 1890 when almost none were driving cars). This number does not mean anything. What would mean somthing is that X% of the divers using computers got DCI compared with Y% of the divers using tables who got DCI. More divers today are getting DCI with computers simply because more divers today dive with computers PERIOD. No inferance can be made from this data. To make and inferance from this data you need to know the following facts: 1.) Total number of active divers in the world in year 2002 on X date. 2.) the number of that population of active divers who use computers and 3.) the number that do not use computers but use dive tables exclusivly. Then and only then can you draw a conclusion about comparing incidents of DCI with computer usage. My money is on the computer as a safer device than the tables, which are fun to work, not eaisly read underwater (small print and age plus water make for fun reading).
Computer usage by a person who has a DCI hit does not,of itself, mean the computer caused the hit. It just means that another diver has had DCI. The only conclusion you can draw is: One of two conditions existed, 1.) the dive is prone to DCS and took what is termed an "underserved hit". This means he/she did everything by the book and still got a DCI hit. Dan recently published an article on this in May/June I thinks, but I have already recycled that edition. If memory serves the most common catagory of DCI was what DAN terms "underserved". Again, I am going by memory, but you can check your back issues of DAN magazine "Alert Diver". Two: the diver violated some diving principal such as too rapid an accent (dive computers have speedometers and sound alarms to help you accent conservativly) or staying down too long.
I also agree that dive computers more accuratly track your dive. Using a dive table, you plan you dive to say 80 feet, but what happens if you slip down to say 100 feet for a few minutes on the wall or reef? It happens and perhaps you don't even notice it? The dive computer captures that information and recomputes, you may not notice, or be able to recompute on the fly. The computer also gives you credit for the portion of the dive spent at a more shallwo depth.
Another advantage of a computer if it is downloadable, it will keep track of your dive, allof it. You will be able to recall only the last few times you checked your gauges, or maybe nothing at all (amnesia has been known to happen in relation to diving accidents). The dive computer will give a clue if it was a rapid accent or too long at depth. At least it is a place to start for the medical types.
I orginally dove a Ocanic Pro - it is more liberal. I now dive a Suunto Cobra and it has user settable preferances. You can choose normal, chicken, or super chicken (ultra conservative) which is my personal choice, then on top of that you can add altitude to artifically make these settings even more conservative.