Dangers of 100% O2?

[Lazlo]

So, I'm back from my hols, and am gradually working through the various RSS feeds to which I'm subscribed, and I've just come across this.

Damn Interesting » Beware the Dangers of Oxygen
and there is a reference to this link which may be considered a bit more authoritative
Oxygen Meant to Resuscitate May Damage Brain: Scientific American

To summarise the bits relevant to we divers:

- Oxygen can be toxic at high partial pressures (natch).
- Conventional wisdom says that if a tissues would die for lack of O2 then obviously it makes sense to introduce (forcibly if necessary) the highest concentration of O2 possible.
- However, pure O2 can have negative effects that can cause:
a) the circulatory system to work less effectively, thereby reducing the amount of O2 taken up, and
b) the brain to have a negative reaction, further reducing effectiveness.

The article goes on to talk about the "brain dies after six minutes without O2" theory, and about how that may only be the case in the first place because of the practice of forcing O2 into (recently) clinically dead patients. Apparently, if they just waited (and tried different techniques), it might be possible to revive more patients.

Anyway, so what do you medical types think? Should we be thinking about stopping using 100% O2? Would, as the article implies, a DAN O2 kit with bottles containing 5% CO2 be much better for us? Was KnitwearMan right after all (perish the thought )?

[IainC]

Interesting, I'll wait for few more peer-reviewed studies and new advice form the 1st aid organisations though :-)

But no way would you want ot mix up a bottle of 95%O2/5%CO2 with anything you might take diving!

Iain.

[Mark Chase]

It hink the hyperbaric doctors who use very high (2.8pp02) partial presures of 02 over several hours to treat scar tissue and other areas of the boddy suffering from poor blood circulation, may disagree with some of these findings.

The reduced up take of 02 in diving terms is the lungs building a layour of mucus to protect from the burning effect of the 02. This is overcome/ reduced by the use of air breaks. However I find that there is a wide spread beleife that air breaks help prevent 02 toxing which I am not convinced about.

ATB

Mark CHASE

[witchieblackcat]

I did a dry dive in the Wirral last November and the guy that gave the talk before we dived was talking about how 100% O2 was a thing of the past and soon we'll all be using heliox (at 50% O2).

[aquaholic]

Originally Posted by Mark Chase

However I find that there is a wide spread beleife that air breaks help prevent 02 toxing which I am not convinced about that.

No,air breaks are ment to reduce pulmonary toxicity. Ever seen the lips and throat of someone straight out of the pot after high levels of O2 over prolonged periods? They are red and sore from the O2.

[Mark Chase]

Originally Posted by witchieblackcat

I did a dry dive in the Wirral last November and the guy that gave the talk before we dived was talking about how 100% O2 was a thing of the past and soon we'll all be using heliox (at 50% O2).

I remember being told the same thing years ago but its still not hapened yet.

Possably due to the cost of Helium

ATB

Mark Chase

[Fee]

I definitely agree with Iain's comment - I don't think that people will change their practice on the basis of one study. without seeing the original it's difficult to comment, but my first thoughts were
1. What tissues do in a dish is not necessarily what they do in a person
2. tests on healthy child volunteers to not necessarily translate to the same results on sick adults
(Obviously both the above methods are used in testing new treatments anyway and so i am not dismissing them - merely saying that one should be cautious with interpretation of the results)
3. unless you have intubated the patient you will not be giving them 100% oxygen. Even a tight fitting face mask with high flow O2 is likely to be giving around 85-90% so you will be getting some CO2 in there.
4. Would you be happy to be a guinea pig for the "wait and see" approach? the only way to tell if this is better is to randomise your resus patients into high/ low FiO2 and I know which arm I'd want to be in!

Will be sticking with as much O2 as i can stuff in my patients for now!

[gibbon]

there is no doubt about it oxygen is highly adictive and everyone who has ever used it will die regardless of the concentration or partial pressure.

[Lazlo]

Originally Posted by gibbon

there is no doubt about it oxygen is highly adictive and everyone who has ever used it will die regardless of the concentration or partial pressure.

And don't forget it's a gateway drug too. 100% of heroin addicts started on O2....

Originally Posted by Fee

I definitely agree with Iain's comment - I don't think that people will change their practice on the basis of one study. without seeing the original it's difficult to comment, but my first thoughts were
1. What tissues do in a dish is not necessarily what they do in a person
2. tests on healthy child volunteers to not necessarily translate to the same results on sick adults
(Obviously both the above methods are used in testing new treatments anyway and so i am not dismissing them - merely saying that one should be cautious with interpretation of the results)
3. unless you have intubated the patient you will not be giving them 100% oxygen. Even a tight fitting face mask with high flow O2 is likely to be giving around 85-90% so you will be getting some CO2 in there.
4. Would you be happy to be a guinea pig for the "wait and see" approach? the only way to tell if this is better is to randomise your resus patients into high/ low FiO2 and I know which arm I'd want to be in!

Will be sticking with as much O2 as i can stuff in my patients for now!

This all makes good sense to me. The paper was only published on May 22 this year, so maybe (hopefully) there will be follow up studies. Who knows, maybe some day it will result in more efficient deco profiles, and maybe even a better chance of success for DCI victims...

[recurve]

Methinks I won't be getting rid of my resus o2 bottle for self and family any time soon!