emergency oxygen what depth do you have it on standby

[briancro]

Hi All

After diving in the blue hole today along with at least another 30 athletes, it suddenly struck me - at what depth do you go to before you make sure that you have an emergency oxygen kit available?

Some people seemed to be going beyond 70m and I could only see my own oxygen set available if anything should go wrong.

Also heard from another freedive only the day before that they suffered a lung squeeze at 35m.

Please do not use the excuse that "one of the dive centres would have one that you could use", :naughtyhaving heard about a certain scenario were an oxygen set was required, it took four sets, before they found one that worked or had oxygen in it. That was in the blue hole only last year.

30m+ or am I just being too catious.

Brian

 

[trux]

Well, I can only speak for my club, and others I know in France. The depth actually does not play any role for having or not having emergency O2. The depth would play a role for O2 decompression only, but we have emergency O2 present even at pool training, at at every diving trip as well, whatever the depth is. In case of an accident, an instructor who would organize training without emergency O2, would be in serious troubles. At trips with beginners, the depth is rarely over 30m, but there is a working O2 bottle on the Zodiac anyway.

 

[chrismar]

A (vaguely) related question, since this has been raised.

Given that pure O2 causes vasodilation to the peripheral and vasoconstriction to the brain, what is the advantage of giving O2 to a now conscious diver after a blackout? Note that I'm not talking about DCS precautions or people with severe squeeze, just run-of-the-mill blackouts that they've now woken up from.

Thoughts?

 

[trux]

Very good question, Chris! I hope some expert will answer in details, but perhaps I can write what I know (it may not be the complete answer, but may help anyway):

It is true that the high PaO2 accelerates the removal of CO2 from the blood and body, and hence it has similar effect like hyperventilation, from this point of view.

However, after the blackout, the oxygen saturation is low, and CO2 concentration high, hence the oxygen is needed to get to the normal. Not sure how fast it happens, but I think at normal respiration, and fully functional lungs, it should happen within several breaths (using an oximeter may be better).

Then, interestingly, oxygen has vasoconstrictive effects on the circulatory system, reducing peripheral circulation - in fact countering so the dilatative effect of the low CO2 (I am not sure whether is has also the inverse - dilatative - effect to the carotid arteries, but I think it may be possible).

And also, when oxygen is administered, additional oxygen is dissolved in the plasma according to Henry's Law. This happens at air breathing too, but to a very limited degree. When breathing pure O2, there is much more O2 dissolved in the blood, and hence delivered to the tissue in sufficient levels even at limited blood flow.

 

[chrismar]

An ex-paramedic brought it up with me after a club member had a blackout in the pool. As per our usual protocol, we had him recovering on O2 afterwards. He mentioned that standard practice was to not administer O2 unless the subject had trouble breathing or other complications, it was not administered because of a blackout alone.

Of course we all know that you can black out from hyperventilation and the subsequent vasoconstriction to the brain, but is that a hypocapnic or hyperoxic response?

 

[trux]

Of course we all know that you can black out from hyperventilation and the subsequent vasoconstriction to the brain, but is that a hypocapnic or hyperoxic response?

As I wrote, the effect of the oxygen is pardoxally oposite - so not a hyperoxic response. And the hypocapnic response will take place only after sufficient volume of CO2 was removed from the circulation, so I would tell that giving oxygen to someone with very low SaO2 is rather wise. The question is how long.

 

[Mullins]

How long does SaO2 usually take to come back up to normal - a few seconds? Clamping an O2 mask on somebody after they've regained consciousness and been helped out of the pool could be a bit pointless in most cases.

Also, I wonder if there's much difference between a BO and a normal, hard dive. After all, some of us would be dropping our Sa02 close to BO on a fairly regular basis. So if we administer oxygen after blackouts simply because the Sa02 is still low, we should presumably do the same after each hard swim. That'd be tedious.

 

[trux]

Yes, I think you get to the normal within a few breaths (so probably within a few tens of seconds). Personally I do not think the oxygen is necessary for proper recovery, but it is possible the early administration after blackout can help reducing any potential damage. The faster you get the brain oxygenated after the BO, the better. Doing it after big breath-holds might be perhaps better too. Finally who tells that not?

Frankly told, I do not know all the details behind the reasoning of O2 administration after BO, and hope some expert will chime in and tell us better. Finally I saw even the biggest experts of freediving physiology (Fitz-Clarke, Shagatay,...) assisting with it, so if it was wrong, I guess they would not support it.

However, even if it is perhaps not necessary for proper recovery, it is clear that the oxygen administration will not harm - on my mind the claim that it will reduce the oxygenation of the brain is incorrect (for above mentioned reasons).

EDIT: at depth competitions the BO is practically always accompanied with some degree of oedema, reducing the lung capacity, so that's another argument for the oxygen. I believe Fitz-Clarke made some statistics at the last depth WC, and the numbers were pretty high - it is possible I do not remember it well, and that I exaggerate, but I have the feeling he found that some 70% of divers come up with certain degree of oedema.

 

[rddk]

From what i know oxigen must be provided in case of really bad Bo, or in depth disciplines if the athlets has serious problems like taravana or lung squeezing, after a samba or a little blackout i think is useless to give oxingen, the person will be ok again withouth any help in 90% of cases, ofc if he say that he can't breathe properly i'll give it to him. Also i've done the DAN insurance so for any problem best thing is call them and ask what is it supposed to do as best manouvre.

 

[shrek]

the club i'm in has 2 sets with 2 bottles in each set all in a waterproof cases so for us it's a no brainer we take it everywere and if in doubt use it as no one is going to argue if someone made the call right or wrong to use it