Neil and Steve I consolidated my response....

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Posted by MHK on July 06, 2001 at 09:35:41:

In Reply to: to MHK posted by Neil on July 05, 2001 at 23:54:14:

I was trying hard not to delve to much into the minutae because ICD isn't really anything to worry about but it appears we'll need to demonstrate why.. I'm leaving the office at noon to drive up to Monterey so if you have follow up's I'll get back to you on Monday...

There have been several studies in this area and the leading studies that you should read are Cowley, Allegra & Lambertsen 1979 and the Kang 1992 and with respect to the vestibular issues you'll want to review the Dueker 1979 study that focuses on Middle ear gas exchanges in ICD..

Why it isn't any thing at all to worry about, specifically with respect to the 165' depth limitation by pimped by PADI is based on the above studies, which were both vivo and vitro, concluded that the Pmax in the countered diffused ear was 48 +/- 10 was the standard deviation and the mean time to reach Pmax was expressed in minutes.. They used Nitrus Oxide in these studies and Nitrus oxide is approx. 20 times more soluble than nitrogen, and substantially more soluble than Helium. So if you assume that the counter diffusion could be domonstrated by breathing nitrogen ( air/EANx ) and then consider the differences in the solubility coefficients that translates into a subcutaneous maxing pressure of about 1500 minutes... A sport diver, or even a technical diver, would never be subjected to those extreme differences in diffusity and it's rare that even a saturation diver would even come close to those exposures..

So for PADI to tell you that ICD is something to worry about and it is therefore better for you to dive deep on air is reckless, foolish and PADI hypocritical crap..

This is the kind of stuff they worry about to scare people into thinking that ICD is a worrisome event but yet they would have you believe that you can *learn* how to avoid narcosis.. It's pure BS..

Let me know if you need further clarification..


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