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It seems from the recent discussion of the German woman getting a serious DCS hit that in some cases people are being trained to consider deepest dive first an inviolable rule. I have maintained that jumping on that as the primary cause of a hit on the profile given is not reasonable - especially since there was a much more serious violation, a rapid ascent from 60 feet, involved. Let's look at the profile again: 45 feet for 35 minutes, 2.5 hour surface interval, followed by 60 feet for 35 minutes. First the difference in depth is only 15 feet. Second a 2.5 hour surface interval is a nice long time for microbubbles, a concern with sawtooth profiles, to filter out. Third, is there anyone out there who thinks she would have been better off going to 60 or 70 feet on the first dive, for the same length of time, and then doing the same surface interval and second dive? Using my Buhlmann tables, 21 meters (70 feet) for 35 minutes makes her an E diver. A 45 minute surface interval is enough to get that down to A. Her surface interval was more than three times that long - long enough to go from G to A. The RNT for an A diver on a dive to 18 meters (60 feet) is 14 minutes, giving 35+14=49 minutes for the second dive, still within the no-decompression limit (53 minutes). And this is adding 25 feet to the actual depth of the first dive. Now put theory aside and apply some common sense. Consider a possible consequence of being dogmatic about deepest dive first: Diver nature being what it is, this encourages actually diving deeper on the first dive, at least dropping down briefly to click in a max depth, to preserve one's options for later dives. Is this reasonable? Again, is there anyone who thinks that it would have helped the diver in this incident to have dropped down to 70 feet rather than staying at 45 on her first dive, other things being equal? If so I would be most interested in a physiological explanation. Bill Mayne
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