Scientific studies on air breaks

[ScubaSamScubaStevesFather]

Like many things in technical diving, air breaks seem to not have a consensus among the scientific and agency communities (eg deep stops, optimal GF, etc).

Looking for any scientific studies that helps shed light on the following:
1) are air breaks effective in reducing oxygen toxicity/seizure hits?
2) if yes, what the recommended air break method is (12/6, 20/5, etc)

I know Simon Mitchel is on here; if someone knows how to @ his user that would be great

 

[Underwater Tourist]

@Dr Simon Mitchell

 

[boulderjohn]

I don't know of any such studies, and I seriously doubt there are any. How would you conduct them?

In all the reading I have done in related issues over the years, I have never heard of oxygen toxicity taking place in shallow water during a decompression stop. One could say that proves that air breaks help, or one could say that there might never have been a need for them in the first place.

Every case of oxygen toxicity that I know of has occurred at greater depths with people using incorrect mixes for the depth. It is usually a labeling error.

The use of air breaks is because of a concern about pulmonary oxygen toxicity. I don't know of any cases of pulmonary oxygen toxicity at any depth. I am not saying it hasn't happened; I am just saying I have never heard of one.

 

[LFMarm]

Also not part of CC procedures where the average pO2 during the dive is significantly higher than in OC.

 

[PfcAJ]

I don't know of any such studies, and I seriously doubt there are any. How would you conduct them?

In all the reading I have done in related issues over the years, I have never heard of oxygen toxicity taking place in shallow water during a decompression stop. One could say that proves that air breaks help, or one could say that there might never have been a need for them in the first place.

Every case of oxygen toxicity that I know of has occurred at greater depths with people using incorrect mixes for the depth. It is usually a labeling error.

The use of air breaks is because of a concern about pulmonary oxygen toxicity. I don't know of any cases of pulmonary oxygen toxicity at any depth. I am not saying it hasn't happened; I am just saying I have never heard of one.

I think studying it wouldn’t be hard. Especially in an NEDU style wet chamber.

PFT before and after. Varying oxygen exposures and gas breaks.

Dry chamber varying the same and recording comventid symptom onset time.

It doesn’t have to be a seizure to be oxygen toxicity.

Anecdotally, I am aware of guys who have had pulmonary symptoms on extreme exposures.

 

[boulderjohn]

Anecdotally, I am aware of guys who have had pulmonary symptoms on extreme exposures.

I am not surprised because I know you know people who have had some pretty extreme exposures. Why not give people a more precise definition of what you mean by extreme exposures?

 

[PfcAJ]

I am not surprised because I know you know people who have had some pretty extreme exposures. Why not give people a more precise definition of what you mean by extreme exposures?

Because it isn’t precise.

16hrs+? Long. Often with extended times at 30’ on oxygen (dry habitat).

I personally have not experienced anything that I can feel, but my longest is only 11hrs.

Working on getting a paper about gas breaks for y’all.

 

[rx7diver]

Aren't air breaks believed to reduce the irritation that lungs can experience when they are exposed to high PO2's for a lengthy amount of time? (I'm trying to recall what I read a long time ago.) Irritated lungs are less efficient for exchanging O2 and CO2, correct?

Isn't the "half-life" for the effects of high PO2 much too long for a 5 min air break (after 15 minutes breathing O2 at 20 fsw) to make much difference with respect to Pulmonary Oxygen Poisoning? But, a 5 min air break can give the lungs some relief from irritation and therefore allow your 1.6 ATA decompression to remain efficient once you switch back to O2? Is this correct?

These are two different things, correct? Irritated lungs vs. Pulmonary Oxygen Poisoning?

Hmmm. I've confused myself. Can someone 'splain this?

rx7diver

 

[OTF]

Good questions.

US Navy table 6 (the common hyperbaric recompression schedule) uses air breaks, perhaps that is based on data from some studies? Could be a starting point.

Isn't there precedence for similar breaks in administering long term medical oxygen - albeit on longer timescales and lower PO2s than in diving or hyperbaric medicine? Surely there are studies on that.

And while we're on the subject of unproven oxtox alleviators what about popping antioxidant supplements?

 

[nickbutcher]

Every case of oxygen toxicity that I know of has occurred at greater depths with people using incorrect mixes for the depth. It is usually a labeling error.

The use of air breaks is because of a concern about pulmonary oxygen toxicity. I don't know of any cases of pulmonary oxygen toxicity at any depth. I am not saying it hasn't happened; I am just saying I have never heard of one.

My tox in 2010 happened at 6m