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I had some e-mail exchanges with Chris Parrett and Karl Huggins about this issue several months ago. In basic scuba training you are taught to consider TAD (time, air, depth). None of the tables actually take into account the *amount* of nitrogen you breath in, based on your size (i.e., lung volume), work load etc. Oh, there are "J-factors" in almost every program that will empirically add minutes to your bottom time and/or deco for cold and work, but nowhere does any program I know of ask you your weight/height/body surface area that might be used to compute your actual dose/kg or dose/M2 of nitrogen. If everyone is a 180lb 24 year old Navy diver doing exactly the same work, then this doesn't make much difference. The tables (or computer algorithms) are probably conservative enough that you are not placed at significant risk. Not too many divers get bent. But your note below reminds me that the explanation of why women may get bent more frequently than men has never been explained satisfactorily. It has even been suggested that men may be less likely to complain of pain (type II DCS)!. Right, check out your wife or friend next time they have baby! Two differences between men and women that might explain considerable variations N2 absorption on the same dive profile are mass (weight) and body fat. Let's suppose that your couch-potato instructor has a SCR of 0.6 L/min: At the most simplistic level (not taking into account body fat composition or surface area, the latter is usually a better measure of drug toxicity resistance than weight), your wife would have to have a SCR of < 0.3 L/min just to get about the same N2 dose on a dive of the same profile. I am sure that her SCR and those of many other women are less than the men they dive with, but *that* much lower? Obviously your wife isn't getting bent, so the tables "work", but they aren't working for some women and this may be particularly true of women (and men) doing repeat dives, multi-day diving or who have high SCRs because they are new to the sport. One recommendation has been to take a day off diving every third or fifth day. This is pretty expensive if you're paying for a live-aboard or a once-in-a-lifetime trip. To pay attention to this variable you need to know how much gas you are actually breathing, not just blowing off. So *now* with rebreathers you can do just that! (I knew I could work this in somehow) You could also make adjustments to the standard air tables too. Why don't we do this? Is this to discourage women from diving? Is it OK that they and smaller couch carrot men are exposed to an extra risk? Safer diving through wiser physiology Peter Heseltine PS If you reply and I don't, it's because I am away for a week, not because I am not interested :-) >>>>>>>>>>>> On Thu, 4 Jul 1996 22:50:23 -1000 Rich Pyle wrote <<<<<<<<<< I am reminded of a funny story. My wife (5'7", 110 lbs, built like a rock climber - she is a rock climber) was discussing diving with a 5'9", 250-lb, built-like-a-couch-potato dive instructor. The instructor said to my wife, "You are more likely to get bent than I am because you are a woman, and women are statistically more likely to get bent than men." My wife asked why women are more likely to get bent than men, and the instructor replied, "Because statistically, women have more body fat."
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