"Deep" (Half) stops

[Marie Falardeau]

FYI NAUI has changed its deep stops recommendations for non decompression (recreational) diving over 40' deep.

It is recommended that following dives in excess of 40 feet (12 m), divers make not a one minute stop but a two to three minute stop (with two and one-half ie 2.5 minutes being optimum) at a depth that is half that of the deepest depth reached during the dive and make a precautionary stop in the 10-20 feet zone for not three to five minutes but one minute before returning to the surface. The precautionary stop time may be considered “neutral” time – not counted as either dive time or surface interval time.

This results from studies by Bennet et al (Undersea and Hyperbaric Medicine 2007;34(6):399-406.

So to recap, now 2.5 minutes stop at 1/2 max depth and 1 minute at 10-20 feet.
Reading further in the study results shows that no advantage was gained by staying longer than 1 minute at 10-20 feet (if the optimum 2.5 minute stop was done at half max depth).

Marie Falardeau
NAUI Scuba Instructor

[Tom Falardeau]

I'd do what she says...

She can get real mean....

Tom Falardeau
Marie's NAUI Dive Biatch (aka Divemaster) :D

[owlbill]

I have yet to read that article, but it sounds good. Some nice forward thinking there.

[blee]

Anyone seen anything in the new standards about problems or contraindications in making a 10-20 foot safety stop longer than 1 min? I would have (uneducatedly) guessed than even on-gassing at those depths would not be significant, but maybe the more knowledgeable (or someone with v-planner) has better opinions.

[Marie Falardeau]

Some of the detail in "Effect of Varying Deep Stop Times and Shallow Stop Times on Precordial Bubbles After Dives to 25 msw (82 fsw):
...the data indicates that the shallow stop is not as important as a deep stop for the profile, but for practical purposes, the original 3-5 min shallow stop could be retained as it also attenuates the risk for pulmonary barotrauma.
Our research seeks to control bubble growth by the intervention of a deep stop to prevent supersaturation at depth and bubbles forming at that time but growing in size with ascent in accordance with Boyle's Law. If the deep stop is effective in stopping this bubble formation, the shallow stop becomes much less important as the present research confirms. This method of decompression may be designated as "beating the bubble" rather than "treating the bubble". ...

[JimC]

This is all very reminicent of what GUE has been saying for years. Deeps stops to prevent bubble formation then "agreesive" shallow stops that make old timers used to Bhuleman M value compartments wince.