ISSUE 20 ARCHIVE - DCI MYTH BUSTED

My dive computer said that everything went perfectly on the dive, how can I have DCI?

Reliable and important as your dive computer is, what it does not know or take into account, are any external contributing factors or your personal statistics. Your dive profile may have been completely perfect and safely administered but your computer will not have allowed for the following:

1. Your Body

   Skinny beanpole or spherical lardball? How much fat you carry, and where it's distributed, could influence a DCI risk: although quite how much is controversial. Fatty tissues hoover up nitrogen and inert gases much more greedily than their less fatty counterparts; but the blood supply to abdominal fat is relatively poor, so it is more difficult for the gas to get there in the first place. These two opposing factors may account for the seemingly contradictory data that's out there. Most would agree, though, that fatter divers are unfitter and more prone to other illnesses (eg. diabetes, heart disease), so watch that waistline.

2. What you did the night before

   Neither sinking 10 pints after an incendiary curry, nor puffing furiously on a sheesha in

   an Egyptian backstreet (or the Edgware Road), are ideal pre-dive activities, but how tempting they are to the diving fraternity. We need not point out the detrimental effects of drinking and smoking on hydration and oxygen carrying capacity to this august readership, but how will your computer compensate for them?

3. Your rate of exertion

   Exercise before, during, and after a dive has wildly varying effects on gas bubble generation. There is some evidence that a good bout of intense exercise 24 hours or less before a dive

   is protective; but heavy exercise during a dive, or on the ascent, is thought to increase gas uptake and promote bubble formation. Conversely, a bit of gentle finning at the safety stop may help you off-gas more efficiently. Woe betide the diver who leaps on the treadmill soon after surfacing however; the hour or two after

   a dive is when bubble liberation is at its peak, and heavy exercise at this stage is likely to result in a bubble-related injury of some description.