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Genesis · 31st December 2006, 18:58

A Type II hit without obvious provocation is a CLEAR indication that you need to be checked for a PFO if you intend to continue to dive.

A Type I hit is not that simple. If you think about it, a PFO is going to (most of the time) produce a Type II cerebral hit if its going to produce one at all - this is just a function of where the blood goes and how your circulatory system is built.

MOST PFOs are exercise-provoked and as such exerting yourself after a dive is a REALLY bad idea, since as 1 in 3 people have one (but most are only provoked by exercise and are quite small.)

The profiles posted without more information don't tell us much. As square profiles they show huge amounts of mandatory deco blown off, so obviously they were not. But - were they sawtooth (a known DCS provoker)? If one or more of them was, then that dive should have been treated as a decompression dive and the schedule followed for the max depth and max time. The computer won't pick up on this - you have to do it manually.

How was the diver's ascent profile? My standard OW "no deco" ascent profile looks a lot more like a decompression profile than a standard "3 minutes at 15'" thing. For a 100' dive I will do short (1 minutish) stops at 50 and 40, 2ish minutes at 30, the standard 3 at 15-20 and then a nice slow ascent to the surface (3 minutes or so for the last 15') Is this "mandatory"? No. Does it lower deco stress? Yep.

The standard OW guys teach what is IMHO an inadequate understanding of decompression theory and reality, all in the name of making the classes "faster" and "easier." Most of the time, this works out ok. But when you start getting aggressive in your diving, and this pattern IS reasonably aggressive, you need to be smarter - or you run the risk of something like this happening.

With all that said the only way to completely avoid a hit is to not dive. It CAN happen "without provocation" and sometimes does.

But - most of the time the truth is that you pushed it just a tad too far, whether due to dehydration, post-dive exertion the profile itself or other factors.

31st December 2006, 18:58	#27 (permalink)
Genesis Bubbless Box of Death Current Rebreather/s: Home Build Other Rebreather/s: Home Build Join Date: Oct 2005 Location: Sunny Florida Posts: 1,453	Re: DCI: What could have triggered it? A Type II hit without obvious provocation is a CLEAR indication that you need to be checked for a PFO if you intend to continue to dive. A Type I hit is not that simple. If you think about it, a PFO is going to (most of the time) produce a Type II cerebral hit if its going to produce one at all - this is just a function of where the blood goes and how your circulatory system is built. MOST PFOs are exercise-provoked and as such exerting yourself after a dive is a REALLY bad idea, since as 1 in 3 people have one (but most are only provoked by exercise and are quite small.) The profiles posted without more information don't tell us much. As square profiles they show huge amounts of mandatory deco blown off, so obviously they were not. But - were they sawtooth (a known DCS provoker)? If one or more of them was, then that dive should have been treated as a decompression dive and the schedule followed for the max depth and max time. The computer won't pick up on this - you have to do it manually. How was the diver's ascent profile? My standard OW "no deco" ascent profile looks a lot more like a decompression profile than a standard "3 minutes at 15'" thing. For a 100' dive I will do short (1 minutish) stops at 50 and 40, 2ish minutes at 30, the standard 3 at 15-20 and then a nice slow ascent to the surface (3 minutes or so for the last 15') Is this "mandatory"? No. Does it lower deco stress? Yep. The standard OW guys teach what is IMHO an inadequate understanding of decompression theory and reality, all in the name of making the classes "faster" and "easier." Most of the time, this works out ok. But when you start getting aggressive in your diving, and this pattern IS reasonably aggressive, you need to be smarter - or you run the risk of something like this happening. With all that said the only way to completely avoid a hit is to not dive. It CAN happen "without provocation" and sometimes does. But - most of the time the truth is that you pushed it just a tad too far, whether due to dehydration, post-dive exertion the profile itself or other factors. __________________ "A venturesome minority will always be eager to get off on their own, and no obstacles should be placed in their path; let them take risks for Godsake, let them get lost, sunburnt, stranded, drowned, eaten by bears, buried alive under avalanches - that is the right and privilege of any free American." http://www.denninger.net http://www.diversunion.org/liability.htm - Fix the Diving Cert racket
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