DCS and freediving

[Kars]

Hi Newwave,
Similar to you I don't have a deep diving spot nearby, max 18m, but what I do for deep diving is learning the required techniques. With some techniques like sub maximum inhale you can practice a lot at shallower depths. Doing my deep dives at my favourite freedive competition event in Sweden, Nordic Deep, in a 3mm suit I've adopted a dry preparation routine in order to keep myself warm. I actually made only 4 deep dives there last year. It works very well for me, and in the last dive things I learned the previous dives came together and it was a beauty, a moment I treasure in my mind.

I rather have quality over quantity.

Love, Courage and Water,

Kars

 

[efattah]

I would like to add that deep dives with rapid ascents will very likely cause bubbles, and any recompression dives after, on apnea or on O2, are essentially using what scuba divers call the 'bend and mend' philosophy. Namely, you get minor DCS and then try to fix it afterwards. This is never ideal.

I also know that the apnea recompression method isn't flawless. I have tried doing repeated 60m+ dives with apnea recompression after, and I still get small DCS symptoms. Maybe with O2 that could be further reduced.

In terms of why I may be susceptible, the fact is that I got minor DCS many times even years ago, I just didn't know it, because I didn't know what the symptoms were. In fact I think many divers get minor DCS and don't even know it.

 

[Kars]

Apparently Eric you've developed a keen eye for the DCS effects on your body, can you tell us what they are?

And how do you know these sensations apart from other sensations like for instance N2 narcosis?

Thank you Eric for your many generous contributions.

Kars

 

[efattah]

I think I mentioned my symptoms in another thread, but here there are again:

In order from MILD to SEVERE:
1. left or right side of one thumb will go numb, other side feels normal (occurs within 30 minutes of end of dive)
2. tingling or numbness in other fingers or toes (occurs within 30 minutes of end of dive)
3. Minor pain in knuckles (occurs within 5 hours of end of dive)
4. Weird 'prickling' momentary 'pins' or spikes in random areas of body near the skin, as if someone was poking me with a sharp object in random places at random times, or as if a bug was crawling under my skin -- perhaps air bubble traveling through skin microcapillaries?
5. Severe pain in knuckle joints, elbow joints, or toe joints
6. Severe weakness/exhaustion (usually combined with all of the above symptoms)

In the last 4 years I have 100% isolated these symptoms as DCS related and not related to anything else. For a while some doctors thought they were, for example, related to cold water. However I proved that theory wrong, because I could dive in cold water for hours at less than 15m and never get any of the symptoms; on the other hand, deep dives in either cold or warm water would reliably produce the symptoms. Similarly, various anti-DCS practices would reduce or eliminate the symptoms.

 

[cebaztian]

Updated:
DCS and apnea


Sebastian

 

[sross]

Just thought I should point out that Physiologists & Diving Medicine practitioners have learned a lot about DCS among freedivers by studying the Ama divers of Japan & Haenyo of Korea. This was going back decades ago. Unfortunately, a lot of it ended up gathering dust in academic journals & conference proceedings, because most of the interest has centred around compressed gas diving & hyperbaric medicine.

You can, however, download an entire book of research articles entitled: "Symposium on the Physiology of breath-hold diving and the Ama of Japan" from 1965, sponsored by the US NAS in Tokyo. Go to this link:

http://books.google.com/books/downl...ut=pdf&sig=ACfU3U1zIwM40woqUt0CT3e9srDPuzjwdg

It's a gold mine of info on freediving physiology (actually, the word freediving wasn't around at the time, technical people called it breath-hold diving in those days) and in particularly on DCS.

In particular- if you go to p. 207 of this book, you'll find the famous paper by Ellis R. Cross that was the first step toward establishing a consensus on whether freediving DCS is a real phenomenon. His paper is still being referenced today. Up to that time a lot of people were claiming that you couldn't develop DCS from breath-hold diving, although many voices in the wilderness, especially Japanese scientists who had seen cases of DCS in Ama divers, had been trying to tell people that you could indeed. After the 1965 symposium, Freediving DCS was considered an established phenomenon.

You can do a google search on taravana, "breath-hold diving", decompression, etc., and come up with a small, but significant no. of articles, mostly from before 1985, and a number of them are written in Japanese, with English abstracts. I'm still reading up on this.

Steve

 

[trux]

There is a new study about DCS in breath-hold diving by our DB resident Dr. Fitz-Clarke, released last month. It may interest some of you:

Risk of decompression sickness in extreme human br...[Undersea Hyperb Med. 2009 Mar-Apr] - PubMed Result

The risk of decompression sickness (DCS) in human breath-hold diving is expected to increase as dives progress deeper until a depth is reached where total lung collapse stops additional nitrogen gas uptake. We assembled a database of all documented human breath-hold dives to 100 metres or greater, including both practice and record dives. Between 1976 and 2006 there were 192 such dives confirmed by 24 divers (18 male, 6 female). The deepest dive was to 209 metres. There were two drowning fatalities, and two cases ofDCS. Depth-time risk estimates for DCS were derived for single breath-hold dives by modifying probabilistic decompression models calibrated with data from short deep no-stop air dives and submarine escape trials using maximum-likelihood estimation. Arterial nitrogen levels during apnea were adjusted for lung compression and decreased cardiac output. Predicted DCS risk is negligible up to about 100 metres, beyond which risk increases nonlinearly and reaches a plateau around 5 to 7 percent when total lung collapse occurs beyond 230 metres. Results are consistent with data available from deep breath-hold dives.

 

[efattah]

Sounds like Fitz-Clarke's study was only about single breath-hold dives, rather than repeated dives.

 

[chrismar]

Sounds like Fitz-Clarke's study was only about single breath-hold dives, rather than repeated dives.

In fairness, it's harder to find people doing 100m+ repeats...

 

[Deepwater]

Have you been tested for a PFO? Do you have an example of your tables that I could look at?