Can freediving cause DCS?

[efattah]

Originally Posted by Ulf

How long were your surface intervals?

Surface intervals were 8 minutes or more.

[Mullins]

Sounds like you must be pretty susceptible Eric, I've done far worse series of dives with no problems. Probably carrying more nitrogen and faster ascent rates at times too (variable weight spearfishing, great fun but easy to put yourself at risk of DCS). Scary stuff. I think the dopiest thing I did was in Dahab last year. Line was set at 90m, pulled up at 80m with an equalising problem so I waited a few minutes and did it again. Completely forgot about DCS....

[EdHornby]

what surface intervals would you recommend? say for 3 separate 40m dives?

[Mullins]

I think the AIDA tables would say 6 mins? That's if I remembered the formula correctly...

[Walrus]

Definitely some people are at greater risk then others. I have a friend that's been bent more then once on scuba doing long dives to only 10m, and was well under the tables. With freediving I've done a few things that others may have gotten DCS from. I've done 10 40m dives in a row doing some monofin testing. I think the rests in between were around 5-8min. To me these dives were on par effort wise with a recreational dive so didn't think much of it. Probably a bit stupid now I look back on it.

Eric has a point to be careful whilst doing repetive diving with a monofin because of the fast acent rates. I think it's also riskier because
not only are you diving deeper with a monofin, but often you forget the depths you are doing because it doesn't feel like a big dive effort wise. To me a 40m dive with a monofin feels like a 20m spearfishing dive effort wise. I've never had any DCS symptoms with freediving. I had a minor type 1 bend from scuba in my shoulder joint a year ago. Now am a bit paranoid so I aim to be a lot more careful with repetitive freediving also. If I had access to the equipment I would definitely like to have an O2 cylinder and do a 5min at 5m deco stop after depth training sessions.


Cheers,
Wal

[immerlustig]

hi,

i'd like to know what these AIDA tables are based on?

bubbles are forming due to increased ascent rates. a freediver will always be ascending faster than a scuba diver (>10-15m/min or 0.16-0.25 m/s) therefore there will be bubbles forming (what's regarded as a slow freedive ascent? 0.5-0.8 m/s?). when symptoms are being felt (or measurable) is a different thing, though. sooner or later the saturation (depth/time) is great enough to lead to dcs symptoms. playing with surface intervalls, breathing o2, etc will only delay the onset of symptoms, reducing the risk but not eliminating it. people can go deeper or dive repetitively more often without symptoms and that is obviously already fantastic.

what i don't quite understand is why dcs1 is occuring. i would have thought that is very unlikely.

anyhow, that's my understanding of the process. if i'm wrong or missed something please enlighten me. i had dcs on 3 different occasions so far, doing repetitive as well as deep dives.

cheers

[Lobo Marino]

Originally Posted by efattah

This is not correct. I got bent 8 times while freediving and every single one was a type 1 hit.

After years of experiments, the primary factor in my hits was the ascent rate. A dangerous ascent speed is much more likely with a monofin, and in my opinion it is much easier to get bent when using a mono.

I was able to avoid DCS by controlling my ascent rate to less that 1.0m/s, with an additional reduction to 0.5m/s in the last 10m. Even better is a short apnea deco stop at 6m, but this can increase the risk of blackout.

For me, I found that with a very fast ascent (1.35m/s), it would take just two 40m dives to get a small type 1 hit.

The worst hit I ever had was in late 2005, during a wall diving session (30m, 44m, 48m, 51m, 30m, 32m). I ended up in the chamber on Navy Table 6 for several hours. Symptoms: tingling & numbness in fingers & toes, extreme unbelievable fatigue and weakness, pain in elbows, wrists, knuckles, and clouded thinking.

Thanks for sharing the information.
I was thinking that type 1 DCS like pain in the joints was linked to slow compartments and therefore rare with freediving but was wrong.
where this dives that get you bend Deep Hangs ?
By the way aren´t tingling ,numbness in fingers and fatigue or clouded thinking the symptoms of a possible type 2 DCS (or even AGE) ?
(involving nitrogen bubbles in the blood stream and/or neurological/nervous system DCS)

UKDivers.net - Decompression Sickness
Decompression sickness - Wikipedia, the free encyclopedia

[efattah]

I never do deep hangs due to the DCS risk, and none of the time I got DCS was during deep hangs.

During my chamber day, all dives were around 2'10" in length with approximately equal ascent and descent times, and a short bottom time of about 5-7 seconds.

Another time I got bent on the Chaudiere wreck, I did 9 dives, 24-38m in depth, average dive 2'44", average interval 6'30", longest dive 3'35" at 24m.

In 2001 I did two 71m dives with a 12 minute interval, no DCS. But, I was ascending much more slowly due to tired legs. In many cases of deep diving, tired legs actually save the life of the diver because they limit the ascent rate.

If people say I'm 'susceptible' to DCS, they should consider that I was ascending (most likely) far faster than most people anyway. Very few people ascend at 1.3m/s, and I don't recommend it.

[Mullins]

How did you manage a 1.3m/s ascent rate - were they variable weight dives or were you deliberately sprinting? Just checked and I was doing 1.1 - 1.2m/s in the last 20m of those VW spearfishing dives.

[trux]

Recently I have found many interesting documents about DCS at freediving, and added them to my database. Some of them are quite interesting. Unfortunately, some of them are not available free in full text, but already the abstracts show some interesting facts and conclusions. Others are available in full extent on the web. Check them out here: DCS @ APNEA.cz

The document about detection of nitrogen saturation through tear film bubbles may be of a big interest for any deep freedivers.

I was also surprised by the freediving DCS/barotrauma mortality claim in the document eMedicine - Decompression Sickness : Article by Stephen A Pulley, because before that I did not hear about any DCS or barotrauma fatality at freediving:

(separating mortality data for DCS from those for barotrauma is impossible. One study reported that pathologists demonstrated little knowledge of diving accidents while performing autopsies and missed the more subtle diving injuries)

In the breath-hold free-diving group, fatalities have steadily increased worldwide over the past decade to 22 in 2004. Note that only 5 or less were related to free-diving competitive activities, either training or competition. Most fatalities were during snorkeling, spear fishing, or collecting of marine specimens.

[unobreath]

DCS.
How you get bent is unknown. It usually happens when your tissues are saturated with nitrogen and off gassing is not done properly i.e. missed deco stops or omitting decompression all together. relying on your computer to let you know you are still in no d limits when in fact you aren't. technology can sometimes fail resulting in injuries, but it is mostly human error. overdoing your limit, over diving your rig, wrong air mix. a number of factors can go into how or why or what causes dcs, A.G.E. and other diving related injuries.

who is immune and who is not is based on genetics. this is why when diving you may get bent but your buddy doesn't yet you have the same dive profile. There are guys at NEDU (navy experimental diving unit) that just can't get bent (within a realm of somewhat safe diving).

DSC may be possible from freediving but I have never treated anyone for dcs or any other diving related injury because of spearfishing or freediving.

Im sure it is possible and has happened but it is just not likely.

anytime you descend into a world we are not meant to be in, the risks become apparent. If we were meant to breathe under water then we would have gills. So dive safe and dive responsible. knowledge can be your greatest ally or your worst enemy.

[trux]

Originally Posted by unobreath

Im sure it is possible and has happened but it is just not likely.

I am not sure if you have read the previous posts, wisdoms of those who already got bent, and/or the documents linked earlier here in the thread. Apparently, DCS at freediving (including accidents, and even fatalities) is much more likely than most freedivers admit, and it does not concern only extreme sled performances as some may believe.

As for the mechanism of DCS at freediving, it is described in the documents linked above. Of course, basically it is quite similar to scuba, but there are some factors at freediving that are not usual at scuba: i.e. high alveolar pressures, rapid changes of intrapulmonary pressures from high positives (packing) to negatives and back again, often amplified by involuntary diaphragm contractions, rapid ascent velocities, high physical effort during ascent, repetitive dives, and more. All that contributes to a risk that cannot be evaluated only based on experience gained from scuba diving.

I highly recommend studying the available documents before doing the conclusion that DCS at freediving is unlikely!

[unobreath]

Originally Posted by trux

I am not sure if you have read the previous posts, wisdoms of those who already got bent, and/or the documents linked earlier here in the thread. Apparently, DCS at freediving (including accidents, and even fatalities) is much more likely than most freedivers admit, and it does not concern only extreme sled performances as some may believe.

As for the mechanism of DCS at freediving, it is described in the documents linked above. Of course, basically it is quite similar to scuba, but there are some factors at freediving that are not usual at scuba: i.e. high alveolar pressures, rapid changes of intrapulmonary pressures from high positives (packing) to negatives and back again, often amplified by involuntary diaphragm contractions, rapid ascent velocities, high physical effort during ascent, repetitive dives, and more. All that contributes to a risk that cannot be evaluated only based on experience gained from scuba diving.

I highly recommend studying the available documents before doing the conclusion that DCS at freediving is unlikely!

Even after reading a few of the posts and links, I still would say it is unlikely to get DCS from breath hold diving. I live in Hawaii and there are quite a few freediver's and spearo's here and not once have I ever treated a person that had gotten DCS from freediving, or even heard of it here or anywhere for that matter. Im not saying that it cannot happen but still as the ratio to people who freedive and the few that have gotten DCS over the last 10 or 20 years I would still say that it is unlikely. But that is my opinion and I am entitled to it. I am sure in a few of these cases if not most they are not giving all the information to why they got bent.

As to my experience... it is not based on scuba diving. I hold some of the highest certifications for surface supplied diving, rebreathers, recompression chambers, and scuba. I am the person you come to see when you get bent.

[Mullins]

So you think it will be fine for me to do 4x80m CW dives in a row with brief intervals? DCS still 'unlikely'?

There are plenty of freedivers around these days who could easily get themselves bent if they were not cautious about surface intervals and # of repetitions. If you haven't come across any DCS incidents, it is probably because you haven't dealt much with this group of freedivers.

[billieball]

I know of cases whereby it would be wise to monitor one's nitrogen loading when freediving and SCUBA diving in the same day. My handy dandy freediving/mixed gas Oceanic Geo dive computer even shows a hypothetical buildup of nitrogen in my tissues after repetitive deep freedives...all to err on the side of caution, I am quite sure. That being said, in my studies it would appear that DCI/DCS is improbable during freediving excursions. Sure, it could happen. It just isn't an issue I would waste too much time worrying about.