Doc, can you please cite the data you referenced for the above claim? I cant find it anywhere, but I am sure you have it.
Hi AJ,
Sure. Klingmann et al 2003 reported 11 cases of IEDCS in 9 divers all of whom (100%) had a major right to left shunt. Cantais et al 2003 reported 34 cases of IEDCS of whom 24 (~71%) had a major shunt and another 4 (~12%) had a lesion that did not spontaneously shunt; a total of 83% with a right to left shunt. It is notable that the same authors found a major shunt in only 12% of control divers who had never suffered DCS. Ignatescu et al 2012 reported 30 cases of IEDCS who underwent PFO testing in which 24 (80%) were positive. Peter Wilmshurst told me recently that he thinks it is virtually 100% and that the few IEDCS victims who don't show a PFO just didn't have their test done properly! That is not published though. Anyway "90%" is a ball park figure, and I was thinking in particular of Klingmann's paper, but there are multiple studies supporting the contention that it is very high.
Refs:
Klingmann C et al. Embolic inner ear decompression illness. Correlation with a right to left shunt. Laryngoscope 2003;113:1356-61.
Cantais E et al. Right to left shunt and risk of decompression illness with cochleovestibular and cerebral symptoms in divers: a case-control study in 101 consecutive dive accidents. Critical Care Medicine 2003;31:84-8.
Ignatescu M et al. Susceptibility of the inner ear structure to shunt related decompression sickness. Aviation Space and Environmental Medicine 2012;83:1145-51.
I have these papers if you would like them.
---------- Post added January 5th, 2015 at 09:47 AM ----------
Secondly, not all deco experts are in agreement on the findings, neither do they dive shallow stop profiles.
I think the truth of this matter is that there would be few, if any, un-conflicted decompression scientists or diving physicians who do not believe there is an important signal in the NEDU study results. By specifying "un-conflicted", I recognise the possibility that there may be one or two who might disagree, but who have a financial interest in deep stop models. That is not to say that their opinion is invalid, but it does raise the possibility of an understandable bias.
Your observation that many deco experts don't dive shallow stop models (
per se) is valid. But the evolution of "expert" decompression practice in response to the emerging evidence reflects sensible caution in the face of incomplete data. My own response to the current situation has been articulated in a number of places, and I recall UWSojourner linked to a couple of those a few posts ago. I think it is also fair to say that many other knowledgeable scientists are changing their practice, but cautiously so.
Simon M
---------- Post added January 5th, 2015 at 09:57 PM ----------
Dr Mitchell, we really appreciate you coming on here and clarifying the information for us. Thanks so much for your patient responses!
Thank you. Its an important subject to discuss. Can I also acknowledge the contribution that UWSojouner has made here and on other threads. His depictions of some of the physiology have enhanced understanding for many divers.
Simon M
---------- Post added January 5th, 2015 at 10:10 PM ----------
Simon, I'm simply not willing to risk bubble nucleation & formation in my Fast Tissues for the sake of not loading/supersaturating my Slow Tissues later on in the deco profile (per indication of those "heat maps" by UW Sojourner); essentially a "Robbing Peter to pay Paul" dilemma.
And yes, I have plenty of time and an 11L Alu full of O2 to clean-up those Slow Tissues. . .
Hello Kev,
I guess this is the sticking point. It is an article of faith for you that allowing fast tissues to supersaturate early in a profile that places less deep stops in your ascent is harmful, and there is probably nothing I can do to change your mind on that. However, I must point out that you only believe that because someone has told you it is so. It is an attractive theoretical assumption that many people believe(d) in the absence of any confirmatory data. The point is, that there is now data that challenge the idea. As UWSojourner's heat maps have illustrated the NEDU deep stops profile did reduce fast tissue supersaturation compared to the shallow stops profile, but this did not result in better outcomes. If tight control of fast tissue supersaturation early in the ascent is as important as you believe, why did the profile with the best control of fast tissue supersaturation early in the ascent produce the highest DCS rate?
Anyway bud, if you do what you say you are going to do and significantly pad your shallow oxygen decompression it may not matter too much what you do earlier. Just don't have a seizure please!
I hope you have a fabulous trip. I may have mentioned I am going back with Pete Mesley in November.
Simon