Lower risk of DCS with conservative profiles in divers w/ & w/o R->L shunt.

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DocVikingo

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It makes me feel warm & fuzzy when science confirms what we have long believed is very sound advice. Hard to believe it took this much time.


“Diving Hyperb Med. 2012 Sep;42(3):146-50.

Lower risk of decompression sickness after recommendation of conservative decompression practices in divers with and without vascular right-to-left shunt.

Klingmann C, Rathmann N, Hausmann D, Bruckner T, Kern R.
SourceHNO-Praxis am Odeonsplatz, Brienner Strasse 13, 80333 München, Germany, Phone: +49 (0)89-290-4585, Fax: +49 (0)89-290-4584, E-mail: info@tauchersprechstunde.de.

Abstract
INTRODUCTION: A vascular right-to-left shunt (r/l shunt) is a well-known risk factor for the development of decompression sickness (DCS). No studies to date have examined whether divers with a history of DCS with or without a r/l shunt have a reduced risk of suffering recurrent DCS when diving more conservative dive profiles (CDP).

METHODS: Twenty-seven divers with a history of DCS recommended previously to dive more conservatively were included in this study and retrospectively interviewed by phone to determine the incidence of DCS recurrence.

RESULTS: Twenty-seven divers performed 17,851 dives before examination in our department and 9,236 after recommendations for conservative diving. Mean follow up was 5.3 years (range 0-11 years). Thirty-eight events of DCS occurred in total, 34 before and four after recommendation of CDP. Four divers had a closure of their patent foramen ovale (PFO). A highly significant reduction of DCS risk was observed after recommendation of CDP for the whole group as well as for the sub-groups with or without a r/l shunt. A significant reduction of DCS risk in respect to r/l shunt size was also observed.

DISCUSSION: This study indicates that recommendations to reduce nitrogen load after DCS appear to reduce the risk of developing subsequent DCS. This finding is independent of whether the divers have a r/l shunt or of shunt size. The risk of suffering recurrent DCS after recommendation for CDP is less than or equal to an unselected cohort of divers.

CONCLUSION: Recommendation for CDP seems to significantly reduce the risk of recurrent DCS.”
 
Was there a definition for conservative dive profiles?
 
I'd love to get my hands on the actual publication. The abstract raises all sorts of red flags with regards to the potential clinical utility of the study.
 
Just saw this cited in the August 2015 Dive Training mag. Can anyone who's read the full publication report either what the conservative profile recommendations were, or if there was some description of the actual change in practices that the participants with shunts followed?

Though it's a small study, the nominal change in DCS events seems remarkable. It would be nice to know what if any changes in behavior might have contributed.
 
Just saw this cited in the August 2015 Dive Training mag. Can anyone who's read the full publication report either what the conservative profile recommendations were...?

Hi spoolin01,

The conservative profile recommendations were use of nitrox with deco times calculated on air tables, no dives >25 msw, no repetitive dives, no deco dives, 5 min safety stop at 3 msw & minimization of Valsalva manueuvers.

Cheers,

DocVikingo
 
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I'm confused. In these recommendations, what exactly is meant by "minimization of Valsalva maneuvers "?
 
Hi spoolin01,

The conservative profile recommendations were use of nitrox with deco times calculated on air tables, no dives >25 msw, no repetitive dives, no deco dives, 5 min safety stop at 3 msw & minimization of Valsalva manueuvers.

Cheers,

DocVikingo

I'm sure if they recommended no diving whatsoever there would have been a 100% absence of DCS. The recommended profiles are ridiculous. I'll wait for the DAN study that is being done now with Doug Ebersole.


iPhone. iTypo. iApologize.
 
I'm confused. In these recommendations, what exactly is meant by "minimization of Valsalva maneuvers "?
A Valsalva manuever especially performed forcefully can increase venous right atrial pressure which can pass N2 bubbles into left heart arterial circulation via a pathological PFO shunt (Patent Foramen Ovale - a persistent opening in the wall of the heart which did not close completely after birth (opening required before birth for transfer of oxygenated blood via the umbilical cord). This right heart to left heart shunt of bubbles bypasses the usual filtering of the Lungs, and can result in Cerebral Arterial Gas Embolism (CAGE), Cerebral Vascular Accident (CVA/Stroke) and/or Type 2 Neurological Decompression Sickness.
 
Thanks, I already understood the shunting and PFO etc. My confusion rests solely on the Valsalva. Is it then the advice to blow gently as one equalizes rather than really honking on it? If that's the case, I'm good because "really honking on it" is against my personal recommendations and my personal style since it's bad for a bunch of reasons not just a shunting problem.
 
https://www.shearwater.com/products/peregrine/

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