Deco stops for Freediving

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ballastbelly

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this article mentions a diver who added breath hold deco stops during the final part of ascent for extreme free diving.

But I am wondering how if is no scuba style exhalation , what sort of off gassing can occur? Thx
 
What article? I would be surprised if a free diver applies deco stops during "extreme free diving". Check out the videos of William Trubridge and his 101m no-fins world record dive (and others) - you won't see any "deco stops" there.

Many articles written by the average journalist get it wrong when it comes to free diving.

Also, the "off gassing" is from the blood not from the lungs so no exhalation would be required anyway (and you would soon be down to residual volume on a single breath of air anyway).
 
You are correct that no nitrogen can be eliminated from the body without an exchange of gas in the lungs. The only theory I can imagine someone having for doing stops while freediving is that the nitrogen from the lungs has been absorbed and might form bubbles in the blood on a rapid ascent. Given that the gas in the lungs does not equilibrate with ambient pressure while freediving (it can't, because the lung volume can't decrease that much), and that the time spent is relatively short (even in extreme dives), I think the likelihood of bubble formation is extremely small, and the risk of stops would not be worth it.
 
It is about getting the dissolved Nitrogen out of the blood stream where it can block flow. It’s fine if the Nitrogen goes back in the lungs. A lot of these Apnea divers are getting bent now — nobody would ever have believed that would really happen 20 years ago.
 
You are correct that no nitrogen can be eliminated from the body without an exchange of gas in the lungs. The only theory I can imagine someone having for doing stops while freediving is that the nitrogen from the lungs has been absorbed and might form bubbles in the blood on a rapid ascent. Given that the gas in the lungs does not equilibrate with ambient pressure while freediving (it can't, because the lung volume can't decrease that much), and that the time spent is relatively short (even in extreme dives), I think the likelihood of bubble formation is extremely small, and the risk of stops would not be worth it.

TSandM - the gas pressure in the lungs does reach ambient pressure all the time while free diving. Lung volume decreases a lot - which is why free divers going beyond about 30 - 38m learn different techniques to equalise (search for "mouth fill" wrt equalising for explanations). Most people can only exhale down to 25% of lung volume (residual volume) so this defines the depth beyond which they have trouble equalising with the Valsalva technique. 25% equates to 30m. Some can go below this using Valsalva or Frenzel techniques if the have a flexible diaphragm (e.g. I got to 36m and an ex-Olympic swimmer I know got close to 40m). Have a look for Frenzel Fattah Mouthfill - there is a paper on this written by Eric Fattah somewhere.

Most of the seriously deep free divers limit themselves to one deep dive each day to avoid getting bent. By deep I mean beyond 60m or so.
 
What article? I would be surprised if a free diver applies deco stops during "extreme free diving". Check out the videos of William Trubridge and his 101m no-fins world record dive (and others) - you won't see any "deco stops" there.

Many articles written by the average journalist get it wrong when it comes to free diving.

Also, the "off gassing" is from the blood not from the lungs so no exhalation would be required anyway (and you would soon be down to residual volume on a single breath of air anyway).


yes they do have deco stops, to me Herbert Nitsch is the master when it comes to free diving, he is after all "The Deepest Man on Earth"

Herbert Nitsch Talks About His Fateful Dive and Recovery - DeeperBlue.com

The original plan was that I would slow down the sled between 100 and 70 meters below the surface on the way back up, and have a one minute decompression stop at approximately 10 meters depth. Because of the blackout due to narcosis (at approximately 100 meters below the surface), I was not able to slow down the sled, and thus it continued on to 10 meters where it stopped as programmed. Fortunately the safety divers brought me right away to the surface.Because this omitted the planned 1 minute decompression stop, the result was serious DCS (decompression sickness), which is equivalent in my case to several brain strokes with severe initial consequences.
 
:) I wasn't thinking of No Limits (NLT) stuff as free diving but instead the more pure "no fins" (DNF) and Constant Weight (CWT) disciplines aka William Trubridge, the two Molchanovas, David Mullins, Jonathan Sunnex etc. (all of whom are capable of over 100m with a mono fin and William Trubrisge holds the no fins world record at 101m).

IMO Herbert Nitsch is deep (and respected for that) but what he has done lately is somewhat suicidal.
 
You are correct that no nitrogen can be eliminated from the body without an exchange of gas in the lungs. The only theory I can imagine someone having for doing stops while freediving is that the nitrogen from the lungs has been absorbed and might form bubbles in the blood on a rapid ascent. Given that the gas in the lungs does not equilibrate with ambient pressure while freediving (it can't, because the lung volume can't decrease that much), and that the time spent is relatively short (even in extreme dives), I think the likelihood of bubble formation is extremely small, and the risk of stops would not be worth it.

supposed case of neurological decompression illness | DeeperBlue.com Forums

I must be especially stupid arguing with a medical doctor, but I think you are incorrect about the pressure in the lungs. The chest cavity compresses a lot. Freedivers work extensively on diaphragm flexibility, rib cage flexibility etc. In addition, the lungs can leak fluid into them and around the lungs as well. I think it may even be plasma leaked from the circulatory system. These mechanisms (and possibly others) do allow equalization of the air spaces with the ambient pressure. These deep divers experience tracheal tears as well, because this is relatively rigid and can collapse and tear leaking blood. They must be very careful not to bend the head to look up, just keep facing forward. For many of these people, they fully flood their sinuses with sea water on the descent effectively eliminating a squeeze or air to compensate for the pressure.

How much of an unequalized pressure differential do you think a diver can withstand without serious injury to the lungs?
 
Yes, I agree with DumpsterDiver overall.

There are several dangers to free diving such as "lung squeeze" which is effectively when the walls of the lungs touch each other when under pressure and stick together and the diver will cough up a little blood. A friend had this happen at the relatively shallow depth of 32m. Chest flexibility and getting your body accustomed to the changes at depth are important. As DumpsterDiver says - tracheal tears can also happen. Keeping your head steady helps avoid this. Another things is to avoid extending your arms as this can help avoid lung squeeze as it keeps your chest stable.

I have been lucky enough to chat to Dave Mullins (125m with fins is his best - just 3m off the word record last year) and dive with Jono Sunnex (3rd best at the AIDA world depth champs late last year). Seems like not too many of the top divers are flooding their sinuses with sea water at present.
 
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