Hypoxia. So you think you can bail?

Lancer4545

Hey Matt,

I have done the very same simulation but it was a Hypercapnia test we were doing......... I am not sure how you would do a Hyperoxia test without a chamber or being at depth.

If you wanted to a Hypoxia simulation pack the scrubber and leave the O2 off. (Not that I would recommend it to anyone to try!!!)

I found my breathing rate increased steadily until I was puffing like a steam train. It was not that I couldn't catch my breath it was an uncontrollable urge to breathe fast. It took around 6 1/2 to 7 mins (if I remember rightly) for the first signs to show and bailed out after 9 mins as I couldn't take any more. I had a shocker of a headache for quite a few hours later too.

It was a valuable learning experience and I now think back to it whenever my breathing becomes faster than normal and then go into some form of recovery drill or bailout.

Regards,

Lance

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CLASSIC TED

Another great thread Brent,I'm sure that of a lot of divers have related to the problems highlighted.
To the Forum Gods watching over our every word, this is why I joined RW to read and hopefully gain an insight into the many pitfalls of our sport and the ways to try and counteract them.
To all you knowledgeable ones "keep em coming"
Ted

Sutty

This is a very good point, thank you for making it - and I confess I haven't had this as a mentally rehearsed response ie even if I feel I have no problem accept the offered reg and at least take a few breaths from it (you do have to trust someone not to give you a bad mix for that depth though, as you must assume you can't judge it properly yourself).

Incidentally I've also done the chamber rapid decompression/hypoxia experience (8000' to 25000' in 3 seconds then take off mask and breathe ambient air). I couldn't write after about 2 minutes and was bad at other tests (eg serial subtractions of 6) before that. I didn't feel euphoric, just slightly anxious and "under pressure", not really bad at all though. Another subject with me got distracted when trying to put his mask back on by a speck of dirt on the floor!
The biggest difference with CCR is that onset is likely to be more insidious and likely not to even be noticed. I've also done the "breathe off ccr with O2 off" (with appropriately briefed trained resuscitation trainer next to me), all I felt was a tiny bit short of breath, and then dizzy - my handsets showed PO2 of 0.05 when I went back to breathing room air.

Neil

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zzzzzzzz

There are some people who have experienced breathing an anoxic gas. How many breathes would you guess it takes for unconciousness to set in? Would it be astounding to find out that few have made it to the fourth breath? It only takes 2-3 to get the lights out effect.

It is doubtful that one could intervene before somebody goes out, even in a gradual hypoxia event. Much like hypercapnia, there is a systemic effect that impairs judgement and that may not be obvious. Victims may be functional all the way to unconsciousness.

Astoundingly, survival is possible. Depth would be a very negative factor wrt survival. Because of the possible reflex responses involved, it is best avoided. There is no guarantee that autonomic responses will yield a favorable outcome.

If a buddy goes out, hope the mouthpieces stays firmly lodged, options involving switch to BOV and ascent may be favorable, while taking care to avoid rapid ascents that may induce embolism. Flushing with O2 may be another alternative. All these scenarios are best avoided as there is no guarantee after the lights go out. Some autonomic responses may cause the jaw to lock up on the mouthpiece, this can avoid drowning, this isn't guaranteed however.

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z

Lancer4545

Diving with a FFM is your best guard against drowning after a hit.

It won't protect you against having the hit but it will stop water entering your lungs and it's a lot easier to resuscitate a diver who has no water in their lungs.

If you have a BOV fitted a rescuer can simply "Bail" you out and you have gas available for the ascent and during the whole rescue which is especially critical if there is any deco commitment pending.

Regards,

Lance

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ISC Appointed Megalodon Dealer for East Australia
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zzzzzzzz

The thing is that procedures for what happens in a hypoxia incident are sketchy. In water, it is likely that the rescuer would have to monitor the victim until he wakes up, a process that can take several minutes. Even with the victim returning to conciousness, the rescuer would have to complete the dive for the victim. The victim would most likely be incoherent for some time. If the victim regains consciousness, it doesn't mean he can manage the rest of the dive.

Wet notes could be handy to bring the victim up to speed on the situation, expect some repetition since short term memory is not going to be there. Best to "follow the leader". Message could read: "Thank you for joining us on the dive, again. Relieved you are back. Feel as though you've awakened from a long slumber? No your slippers or usual breakfast? This is not a dream. Please just keep diving with us."

A FFM with BOV does eliminate a few variables with regard to water ingress and getting a survivable mixture to the victim.

Either way, a flush or switch to BOV is going to be hard to manage with a long ascent. Mostly because the rescuer may think the victim is "gone", which he may very well be.

On second thought wrt flushing the loop, the ascent and falling PO2 would be an issue. Thus, a switch to BOV may be less work for the rescuer. Buoyancy management is one of the major logistical burdens.

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z

Lancer4545

Hi Z,

The chance of the rescuer being relieved of the rescue by the victim is very very unlikely and I wouldn't even consider it an option.

The FFM will stop the victim spitting the DSV or BOV when they are in the "Tonic Phase" of the hit and this is the critical time when most divers drown.

The rescuer only has the simple task of twisting the knob on the BOV and the victim is now bailed out to OC and has a "Known" gas to breathe. Now whether the rescuer has time, and he very well might have during a deco stop if required, he can decide if there is any advantage in flushing the loop and putting the victim back on the loop. The advantage of leaving him bailed to OC is you can tell if he breathing by the exhaled bubbles and you can also tell if he stops breathing......

Forget about any possibility of him doing much for himslef so the less work you have to do the better chance you both have of surviving!!!

Sobering thought....Isn't it???

Regards,

Lance

__________________
You can run but you can't hide!

ISC Appointed Megalodon Dealer for East Australia
http://www.closedcircuitdivers.com.au
info@closedcircuitdivers.com.au

zzzzzzzz

Already have the t-shirt.

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z

g3stanton

"It is doubtful that one could intervene before somebody goes out, even in a gradual hypoxia event. Much like hypercapnia, there is a systemic effect that impairs judgement and that may not be obvious. Victims may be functional all the way to unconsciousness."

While I agree there are no absolutes and your point is well taken, I have personally witnessed cases where the CCR diver exibited signs of distress that required encouraged bailout. My point here is that while we should continue to train conservative resource management, shit happens. When it does, I feel an observant buddy can be a life saver.

Gregg

zzzzzzzz

We absolutely agree Gregg! Your surmise that intervention is key and encouraged bailout can be a lifesaver. It is harder when a buddy doesn't usually make sense anyway, hypoxic can sometimes mimic regular idiocy. ;-)

Do you still have the pickup?

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z