NDL Times

[redacted]

Dr Deco once bubbled...


Open a screw-capped bottle of soda pop. If do quickly, it will bubble. Performed slowly, the liquid will remain largely quiescent. You are not decompressing the liquid in the sense that the dissolved gas is gone. What you are doing is preventing the sudden Boyle’s Law expansion of nuclei with its concomitant reduction in the Laplace pressure (= surface tension pressure that contracts the bubbles). Slow depressurizations will keep bubbles small. None of this is built into tables or deco meters. You can do it yourself for no cost.

I know that this is not simple to visualize. It is simple in principle but not necessarily easy to see.

And would shaking that bottle, before or after opening it, be comperable to the effects of work during or after the dive?

 

[leadweight]

I remain fascinated by this topic. Not only the technical aspects that Dr. Deco and other experts contribute but the intangible factor regarding how divers, especially recreational divers, approach the safety issue. Some of you may have noticed another thread on diving nitrox within the air no stop limits. Divers, especially recreational divers, are willing to make all sorts of choices to enhance their safety by limiting bottom time or breathing nitrox when the benefits are theoretical. How intangible can you get?

Meanwhile, I am giving serious thought to telling DM's that I have a bad back so they will hoist my rig on board.

 

[Dr Deco]

Dear Readers:

Activity

It is a curious phenomenon that folks will prefer to do all types of activities that will contribute to safe dives if they involve technology in the form of some gizmo. They will buy a new meter or table or use a new gas. All good. However, the avoidance of stain and exertion is quite simple, costs nothing, and is self-rewarding.

I always try to get people to do the physical work for me (e.g., cutting the grass in the back yard) and I tell them that I am avoiding DCS. They don’t believe it for some reason – I don’t know why.:mean:

In diving, this avoidance should be a sure fire winner if you could swing it. Seriously, slow and steady wins the race.

Dr Deco :doctor:

 

[TheDarknessLord]

Hi leadweight,
Yes you are right, I was checking the same thing but not in computers, but in tables, and they are totallz different!
So my question is: Which is the right one? I guess the table from the Agency that you come from...... Pretty bad answer!!!

 

[DivingDoc]

Dr. Deco once bubbled:

"The “Pyle stops” are a type of deep stop."

What are the "Pyle stops?" How does one do them and do they apply to no deco diving?

ET

 

[Dr Deco]

Dear Diving Doc:

Pyle Stops

These were named after Richard Pyle, an ichthyologist who works for the Bishop Museum in Honolulu. They are essentially a stop for about two minutes at a depth halfway between the bottom depth and the depth of the first stop as indicated on a table for that particular dive. They are said to result in decompression that leaves the diver feeling better. The effect is ascribed to the reduction in gas micronuclei growth and the consequent effects during the remainder of the decompression.

Dr Deco :doctor:

 

[Charlie99]

DivingDoc once bubbled...
Dr. Deco once bubbled:

"The “Pyle stops” are a type of deep stop."

What are the "Pyle stops?" How does one do them and do they apply to no deco diving?
ET

http://www.bishopmuseum.org/research/treks/palautz97/deepstops.html has the interesting story of how he inadvertantly discovered deep stops. Deep stops were also independently discovered by Okinawan pearl divers, Hawaiin fishermen and also WKPP.

A more technical, less readable article on deep stops is http://www.gap-software.com/docs/deepstop.pdf.

Yes, they definitely apply to no deco diving. They are not required, but doing them makes "bubbling" (circulating gas emboli, aka doppler bubbles) both less likely and less severe.

Deep stops are simpy some additonal short stops deeper than a normal safety or deco stop. These stops let the fastest tissues offgas a little bit, reducing the pressure gradients that have been found to cause bubbles in the venous system.

I have found that deep stops make the same sort of "lower fatigue" difference that many divers report as the result of diving Nitrox.

You get the same effect of deep stops by a good multi-level dive profile. For example, instead of doing 25 minutes at 80', then going directly to 15' safety stop, you are better off doing the 25 minutes at 80', then looking around at 50' for a few minutes, then 30 for a minute or 2, then on up to 15'.

You can also generate deep stop profiles in most deco programs, such as GUE's Haldane-based Decoplanner by using the Gradient Factor options.

Charlie