Breath Hold Diving After Scuba Diving: is it a risk of DCS?

tittygrouper · Jul 14, 2011

Hi, apologies if this question has been asked somewhere already on this forum...

I was recently wreck diving with a buddy of mine, when he ran lower on air I returned him to the boat (after completing a safety stop) & then continued my dive with another buddy. Our dive profile was fairly ordinary, depth 29 meters & bottom time of around 48 minutes, although I think when my buddy surfaced due to running lower on air his bottom time was around 29 minutes. My buddy returned his scuba gear to the boat and then started snorkelling around performing "duck dives"/short breath hold dives. When I returned later on after my dive I noticed this and suggested to him that he should probably avoid doing breath hold descents like he was just in case of any increased DCS risk. I'm not sure if there is any evidence to support this, is there any possibility that breath hold diving following scuba diving could increase risk of DCS?

bleeb · Jul 14, 2011

This topic does indeed come up once or twice a year (relatively infrequently and scattered over several different forum, so it can be understandably hard to find). One thread is here: Scuba and freediving on the same day

The short answer is that breath hold diving below the surface shortly after scuba likely does increase the risk of DCS, although not everyone is convinced.

currier · Jul 15, 2011

Without fully understanding the math / science associated with the risk of DCS due to freediving after scuba, I only follow advice given me by an instructor once upon a time ...

don't do it!

I think your recommendation to your buddy was fair and accurate enough, tittygrouper!

DevonDiver · Jul 15, 2011

The primary issue relates to the possible existence of sub-clinical/non-symptomatic bubbles in the diver's body post-dive.

Re-pressurisation (descending to depth) will shrink these bubbles and allow them to pass through various tissue barriers into parts of the body where they wouldn't normally be able to reach.

Unlike a repetitive scuba dive, the rapid ascent associated with a breath-hold dive would not give those bubbles time to dissipate on ascent.

Once through certain tissue barriers, the bubbles may have the opportunity to coalesce and merge/join, to create bigger bubbles, thus amplify any clinical/symptomatic DCS effects.

As Currier stated: Don't Do It.

Mr Carcharodon · Jul 15, 2011

This was discussed in the last issue of the DAN magazine. They suggested that for commercial divers that do many dives over the course of a day that this could be an issue, but for typical recreational dives this risks were low. Of course for evaluating your particular case we would need more information. A "29 meter dive for 48 minutes" could have an average depth is 25 meters or 10 meters and the end result will likely be very different.

Togalive · Jul 15, 2011

Overall, most recreational divers following safe diving practices can free dive after diving with no problem or worry of DCS. It is typically only after free dives to extreme depths where you would risk DCS from bubble coalescence. Given all of the saftey factors built in by tables and computers, you would typically have to have violated a NDL or come very near it to seriously risk getting DCS from freediving to any normal depths. If that is the case and you have violated an NDL, then you have bigger things to worry about.

Case in point, come up to the Northern California coast and you will see plenty of divers who go out scuba diving for a few hours, and then come back to shore, drop their gear, and head right back out to go Abalone Diving.

Also, as was mentioned above, there is a great article published by DAN on the subject.

While you personally won't find me free diving after scuba diving, its a decision every diver must make like so many others.

DevonDiver · Jul 15, 2011

Togalive:
Overall, most recreational divers following safe diving practices can free dive after diving with no problem or worry of DCS.

Can you cite an authoratitive source for that advice? If not, it is worth ensuring that viewers understand it is only your opinion. If that opinion is qualified, then you should explain how...

jmasin · Jul 15, 2011

The doubt over freediving after scuba diving has caused significant disappointment for me, as I LOVE freediving. I'm not great at it, but the absolute quiet involved when you aren't blowing bubbles has always been such a zen for me...

But out of concern for this topic, I've stopped doing it at the end of the day. Just not worth the unknown risk in my opinion.

DevonDiver · Jul 15, 2011

When I worked in Thailand, we had a very well-regarded Freediving school near our centre. Our students often had an interest in attending their courses. The Freediving school implemented a 24hr minimum off-gassing time. At the very least, I would advise that a general 'rule-of-thumb' procedure would be to utilise your tables 'Flying After Diving' recommendations - or follow your dive computers 'No-Fly' recommendations before free-diving.

That may sound like over-kill, but I really don't like to see people get bent (and I have, a few times).

VooDooGasMan · Jul 15, 2011

Actually, an Island in the south pacific, has a dive outfit called toidiruoy Island divers. Air is hard to get for most of the village, so they scuba all the seafood they can get, then freedive the rest of the day harvesting, they have been doing this for decades. These divers are very impressed as they were told the island was named after them. With little education, to this day, they have never said the name of the Island out loud backwards.

I have done it, but no Extreme depth and only short dives.

Breath Hold Diving After Scuba Diving: is it a risk of DCS?

Please register or login

tittygrouper

Registered

bleeb

Contributor

currier

Contributor

DevonDiver

N/A

Mr Carcharodon

Contributor

Togalive

Contributor

DevonDiver

N/A

jmasin

Contributor

DevonDiver

N/A

VooDooGasMan

Contributor

Similar threads