ISSUE 19 ARCHIVE - DRINKING AND DIVING

Dr Oli Firth

The hazards of drinking are probably the last thing that you want to read about at any time of year, and a lot less so as we approach the festive period, however when it comes to diving & alcohol, we do need to get serious.

C2H5OH. Looks innocuous enough, but these few letters and numbers represent a psychoactive drug that's been in (ab)use for thousands of years.

Despite the initial surge of good humour, sociability and removal of inhibitions, alcohol quickly becomes a potent central nervous system depressant which dulls co-ordination, impairs reasoning, damages memory and disrupts sleep. So apart from daily nausea, eye splitting headaches and hazily recalled evenings, what other dangers do divers who over- indulgence in booze create?

DEHYDRATION: Why does putting away a skinful of liquid one night lead to ones brain furiously trying to break free from one's skull the next morning? Basically because alcohol stops production of the body's anti-diuretic hormone, in essence taking the break off the bladder and causing excessive peeing and fluid loss. The brain is especially sensitive to this dehydrating effect, and this, together with the toxic by-products of alcohol breakdown in the liver, curses us with the throbbing headaches we know and love.

Of course this may be exacerbated by the emission of supplementary bodily fluids from either end of the gut (typically in a projectile manner over porcelain, or if you're not so quick, the pavement).

HYPOTHERMIA: Although a cheeky nip of whisky may reputedly warm the cockles, alcohol actually causes the opposite effect. By dilating blood vessels in the skin, blood flow is redistributed from our body's core to its peripheries, where heat is lost more quickly. If you add in the massive cooling effects of immersion in water and the breathing of dry compressed gas, a diver with alcohol in their system will end up particularly prone to hypothermia.

HYPOGLYCAEMIA: One cause of the after-binge munchies is a drop in blood sugar (glucose). You might think all the sugar in beer would raise blood levels, and initially it does; but as the body's insulin gets to work removing it from the blood, it overshoots, leading to low glucose levels (commonly rectified by a large portion of cheesy chips with your kebab). Diving puts a considerable amount of strain on the body's muscles, and since their main fuel is glucose, it's not a good idea to start a dive with a low level.

DCI: Risk of decompression illness is also theoretically increased by alcohol. The explanation goes like this: firstly, alcohol speeds up peripheral circulation, leading to increased uptake of nitrogen. Secondly, it makes the blood thicker, due to the dehydration

it causes. And thirdly, it reduces surface tension in bubbles, which might promote their growth and turn ‘silent' bubbles into ones that cause symptoms. Although never directly proven, the net effect of all this could be physiologically disastrous, particularly over a period of repetitive diving (your typical week in a hot Sharm, say). All in all no one is saying that you must live a dry and dull life of mineral water and panda pops for the duration of your diving career, but by engaging in some awareness of how alcohol

can effect your dive, and your safety, we will be able to sleep a little sounder at night.

How to balance your alcohol intake

• Try to keep a lid on the amount of alcohol drunk, ideally all the time but especially during a diving trip.

• Don't drink alcohol for at least eight hours before diving, and at least an hour afterwards.

• Don't dive with

  a hangover (this suggests significant dehydration)

• Do drink water, and lots of it, even of you don't have a hangover.