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Drugs and Diving - Alcohol

Dr Jules Eden, dive medicine specialist and founder of e-med, answers divers' questions - as published in Sport Diver magazine:
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Q - What is beer diving?

A - 1. A diving trip to a fishing village in East Devon.
2. A bizarre extreme sport which involves jumping off a dock and catching a beer whilst performing a trick mid-air, all before hitting the water. Points are awarded by judges based on whether the beer is caught, the difficulty of the trick, and the “grace” with which it is executed (although as many participants are of the American obese variety, grace points are infrequently given out). Check your local video browsing website for comical excerpts of this explosive new pastime.

Q - Is there some sort of guide as to how quickly alcohol is eliminated from your system? I'd like to be able to estimate how long it takes for me to be alcohol-free after one beer, two beers, eight beers… If one or two post-dive drinks turns into a big binge night, at least I can then make an educated guess as to when it's safe to dive again.

A - There are rough guides to the rate of alcohol detoxification but it varies a lot from person to person. Some of the factors involved are:

• Age – elimination rates slow as we get older;
• Gender – females generally clear alcohol faster than males, although the increased body fat and smaller size of a woman do lead to higher blood alcohol levels;
• Race or ethnicity – alcohol is broken down by a liver enzyme called alcohol dehydrogenase. Levels of this enzyme vary between races, being high in Europeans and sometimes almost non-existent in Asians or those from the Americas (hence the violent facial “flush response” sometimes seen);
• Physical condition – the rate of alcohol elimination varies with weight, and increased physical fitness will speed it up to some extent;
• Amount of food consumed before drinking – food slows down the absorption of alcohol;
• How quickly the alcohol was consumed – multiple shots or drinking games may overwhelm the liver, which can only process about one drink per hour;
• Use of drugs or prescription medicines – these can often interact with alcohol and exacerbate its effects.

Having said all that, the average human with an intact liver will burn up about one unit of alcohol (which is 8g) every hour. A pint of 5% beer these days is nearing three units, so reckon on three hours per pint for full clearance. It soon adds up.

Q - Myself and my diving friends are taking our mate to Egypt for his stag night next month. We plan to live it up and party all night and then spend the days taking in the Red Sea highlights. We are bound to still be a bit merry in the morning with what we have planned, any tips on freshening up for the dive?

A - Being merry in the morning probably means you’re still drunk, so I’d lay off diving and do some sight-seeing if this is the case. Vomiting through a regulator is not much fun. But in terms of “what’s the best cure for a hangover”, the answer is: prevention, or a brace of raw eggs, a hot sauna, kidney dialysis and a lemon wedge rubbed under your drinking arm. Placebo or just weird for the sake of it, who knows. In the real world, try to pack down some water before you hit the sack, preferably with some painkillers and an antacid or milk. Vitamins and anti-oxidants will help (Berocca or Alka Seltzer get my vote.) The next morning, a good dose of O2 (via a run if you’re up to it), more fluids and you’ll be well on the mend.

Q - I have a question about alcohol and pressure. Although I don't drink and dive, I'm asking purely from a scientific point of view: if there was alcohol in my blood, would its effects be augmented by depth and pressure, in a similar way to a gas (such as nitrogen, or carbon monoxide etc.)? Obviously alcohol is a liquid, not a gas (unless your beer has been in the sun far too long), but would the effect of having 1 beer and then diving to 20m have the same narcotic results as guzzling 3 beers at the surface? And what about alcohol with bubbles in it: what would happen under pressure if you drank and dived on champagne?

A - An interesting question, and not one that has been investigated, to my knowledge. One point here is that the narcotic effect of nitrogen when diving is due to it dissolving in the blood, ie. it exerts its “martini effect” in its liquid state. Alcohol and nitrogen are additive, so one beer at the surface would definitely feel more like 3 when at depth. Luckily the nitrogen wears off quickly after ascent (one big advantage over alcohol – perhaps we should serve nitrous oxide in pubs, although they might blow up from time to time). All the gas bubbles in a fizzy drink are contained in the gut, and although they speed up absorption of alcohol, they don’t pass into your blood themselves – they sneak out as judicious belches and tummy squeakers. No real risk of an exploding diver therefore, just one expelling bubbles from both ends.

Q - I'm really lucky as it seems no matter how much I drink (and being a student that is quite a lot) I never wake up with a hangover or any other problems other than being a bit tired (and usually a few cups of strong coffee sort that out). I've just joined the University diving club and am learning all about decompression sickness, it says in the manual you shouldn't dive after alcohol but if you feel fine what's the problem?

A - You must be one of those lucky people who can clear alcohol from their system quickly. There is a three or four fold variability in the rate of alcohol elimination by humans, due to many different factors (which I’ll go into later). Crucially though, feeling fine does not necessarily equate to physiologically being fine. It’s a bit like narcosis, or DCS – denial or lack of insight is one of the hallmarks of alcohol intoxication (as exemplified by those urgent 3am pleas to police occifers that you’ve only had tee martoonis). Judgement is impaired and reaction times reduced at relatively low blood alcohol concentrations, at which you may not be aware of the effects. Mix in dissolved nitrogen, and the physical effects of alcohol I’ve already alluded to, and you have a fiendishly unpredictable cocktail of influences on the brain to deal with. The question of coffee is a controversial one: many studies have now debunked the myth of low-moderate amounts of coffee causing dehydration. Although caffeine itself is a stimulant (to urination as well as to the brain), the fluid volume in a cup of coffee offsets this so it ends up being pretty much neutral in terms of fluid balance. Many soft drinks contain caffeine too, and excessive consumption will lead to an overall fluid loss. So, as usual in life, everything in moderation.

Q - I've noticed recently, in a few dive magazines and forums, that people are saying it's OK to drink beer between dives during a surface interval. Being Australian I'm partial to a cold stubbie or ten, and I know some divers who insist on drinking beer before, during and after their dives. Are there any real dangers in this or is it all scaremongering?

A - I read somewhere that "alcohol can never make you do a thing better, it can only make you less ashamed of your mistakes." This makes sense when I've had a few beers and then try to play pool. I'd love to tell you it's all a load of rubbish but, sadly, there are good reasons not to overindulge when you're diving.

One of the myths is that small amounts of alcohol aren't a problem. One drink does actually produce a measurable decline in performance, with diminished awareness of cues and reduced inhibitions. Another important point is that the deleterious effects of alcohol are consistently underestimated by people who drink. One study involved videotaping 13 divers performing pool dives at different blood alcohol concentrations and rating their injury risk. They had objective "sobrierty" tests and rated their own performance afterwards – at higher alcohol levels, injury risk was increased but divers weren't aware of their degraded performance. Other research has shown that there is a definite reduction in the ability of the individual to process information, particularly in tasks that require undivided attention, for many hours after the blood alcohol level has reached zero. This means that the risk of injury in a hung-over diver is increased significantly, particularly if high blood alcohol levels were reached during the drinking episode. Deaths have been directly attributed to excessive alcohol consumption, as it exacerbates the effects of nitrogen narcosis and can lead to drowning. In addition to these dangers, we all know that alcohol causes dehydration, through a direct diuretic effect on the kidneys. Dehydration is considered to be one of the prime causes of decompression illness.

Alcohol is cleared from the blood at a predictable rate, so a beer or two in the evening is unlikely to impair diving the next day, but I'd definitely steer clear of alcohol before or between dives. A votre sante...

(other dive medical questions)


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