Hypoxia

[rbdave]

Has anybody on the list experienced Hypoxia on their units and been able to react in time?

Cheers

Dave

[saturated]

I've experienced it in a chamber under controlled conditions. My experience was that I had no physical symptoms prior to black-out. Scary stuff.

[jepuskar]

You see, just another reason to justify to use PO2 monitors. I know a couple people on this board alone who will refuse to dive a rebreather without one.......and because of that, they have a good chance of being around for awhile.

I also heard that hypercapnia sneaks up on you too. The lack of CO2 sensors for rebreather divers really aggravates me. I have been in contact with several manufacturers of CO2 sensors, but I think they are just not capable. I dont quite understand this yet, but damn...this can be solved.

[rbdave]

I agree with the comments about all units should have ppo2 sensors. I now dive an inspiration which is great.

However before this unit I used to dive a homebuilt which initially did not have ppo2 monitoring. It relied on me counting my breathes. Which brings me to the reason for my post. I experienced the effects of low O2 and it is noticable prior to blackout.

There is a general sense of well being and a mental slowing. I doubt that I would have recognized it but because I was counting my breaths it became apparent. I reacted instantly grabbing my OC but as I did my feild of vision collapsed to tunnel and then nothing. I had spat the loop but not quite got the reg in when this happened. I was on deco at 3 metres at the time and had made 2 quick kicks toward the surface. The last kick I made had no power but it was enough to get me to the surface at which point my vision instantly returned. I had gotten my oc in my mouth but spat this upon reaching the surface. I was diving solo at the time so would certainly have drowned.

I personally find Hypoxia way more scary than hyperoxia but there is a very small window in which to react.

Perhaps this post will help someone to react at that critical time.

I hope that none of you are ever there as I suspect most cases probably end in fatalities.

Cheers

Dave

[The Iceni]

rbdave once bubbled...
Has anybody on the list experienced Hypoxia on their units and been able to react in time?Hi Dave,

It is generally accepted that you will have very little warning of impending hypoxia and simply lose consciousness within milliseconds of vision dimming - if that is experienced. You were VERY lucky. Do you know why you suffered dilution hypoxia? Was it a failure of both injectors?

Ever tried to stop yourself from fainting? It is a similar situation.

I would not recommend this; but when we were children we experimented with hyperventilation followed by breath-holding sitting on the edge of our bed. Unconsciousness resulted every time!

We lost consciousness due to the reduction in oxygen before the carbon dioxide level rose sufficiently to produce the reflex urge to breath. This is because the prior hyperventilation flushed out all the CO2.

Free-divers?????? :eek:

[fins wake]

I also heard that hypercapnia sneaks up on you too. The lack of CO2 sensors for rebreather divers really aggravates me. I have been in contact with several manufacturers of CO2 sensors, but I think they are just not capable. I dont quite understand this yet, but damn...this can be solved.

As several people on this board have indicated, CO2 sensors are being developed by APD for the Inspiration and seem to exist for the elusive Infinito.

But let's not kid ourselves! :hmmm:

Even if functional and reasonably cheap CO2 sensors are developed - and it's a much more difficult issue than first meets the eye - it's just another set of sensors to evaluate carefully under water. Are they working? Are they out of line? etc.

Today's solution is to carefully follow manufacturer guidelines and not exceed them! I strongly suspect that will be standard operating procedure even if CO2 monitoring is successfully implemented.

In fact, I could envisage problems if people run their scrubbers way beyond guidelines and then, in the middle of a deco dive at 50 metres suddenly get a 15 minute breakthrough warning with a 40 minute deco obligation ...

Sorb is cheaper than your life. Just switch it when it should be switched and you'll be fine.

[Mverick]

Dr Paul Thomas once bubbled...

I would not recommend this; but when we were children we experimented with hyperventilation followed by breath-holding sitting on the edge of our bed. Unconsciousness resulted every time!

We lost consciousness due to the reduction in oxygen before the carbon dioxide level rose sufficiently to produce the reflex urge to breath. This is because the prior hyperventilation flushed out all the CO2.



We used to do this as kids. In a little different way.

Bend over a little and start taking deep breaths flushing the lungs. Quickly. Hyperventilating.

Take a last deep breath, hold it and stand up.

Have a friend that's behind, wrap his arms around you like a bear hug and lift you off the ground. While you tilt your head back.

Within a short time you'll faint. 20 to 30 seconds if I remember right.

Friend gently sets you onto the ground.

Little different way's of coming back. Some people convulse. Some just wake up.

Feels like you fell asleep. Lots of time you remember a small dream that happened during the time you were out.

Once you start to faint though. You go fast....... I would say you notice the world closing in and wham you're out.

Let's you know how fast it is by trying it.

You'd think as kids we would have something better to do.

That's one thing that kinda freaked me out about free diving. Same ritual at the surface. Difference being nobody lifting you off the ground with pressure to your lungs.

[caveseeker7]

... Dave,
solo diving a RB and doing so without pO2 monitoring, that's a double whammy. Your guardian angel must have callusses. ;)


fins wake once bubbled...
Sorb is cheaper than your life.
Wise words.

[saturated]

You were extremley lucky,

Everyones physiology is different, when I did the chamber tests some individuals did notice "the tunnel effect". But the majority of us just blacked out with no precursors. The only way to survive hypoxia is to know your ppo2. Flying blind is a good way to become a statistic. The golden rule, Know your po2.

[jepuskar]

That is a neat little experiment to try..although im not going to.


Although, I wouldnt mind going for a chamber ride one of these days.

In fact, my local hospital has a chamber..I wonder if I could go for a ride...hmmmmmm

Time to bring the video camera. :)

[rbdave]

I agree that I was very lucky and once the lights start to go it is too late however I was being effected prior to this and was already reacting when this happened.

Paul asked why I suffered dilution hypoxia. It was on a homebuilt RB which relied on counting breaths and manual injection. I did probably another 70 dives on the unit without electronics but started and finished on pure O2 which was much easier.

I'm now very careful about monitoring my ppo2 but I still enjoy diving by myself ( even after resuscitating an Inspiration diver that had drowned at 42 metres only 2 weeks ago)

Cheers

Dave

[caveseeker7]

rbdave once bubbled...
I'm now very careful about monitoring my ppo2 but I still enjoy diving by myself
By now you ought to know the risks better than anybody. But you might want to have a look at Madmole's write-up of Inspiration accidents. Quite a few happened on solo dives ... . :(
http://www.btinternet.com/~madmole/DiveMole/DMDanger.htm


rbdave once bubbled...
even after resusiting an Inspiration diver that had drowned at 42 metres only 2 weeks ago
What happened ? And why?

Good luck ;)

[The Iceni]

Mverick once bubbled...
We used to do this as kids. I am often amazed that the majority survive childhood intact!

I remain concerned that dilution hypoxia is a common phenomenon with all kinds of rebreathers, when combined with solo diving - another common rebreather practice - this can be fatal.

It would seem we still have a lot to learn about the physiology of rebreather diving.

[fins wake]

I'm now very careful about monitoring my ppo2 but I still enjoy diving by myself ( even after resuscitating an Inspiration diver that had drowned at 42 metres only 2 weeks ago) I gather that Wino's Inspiration accident was due to hypercapnia, not dilution hypoxia? Perhaps merely a question of exceeding official scrubber times again? (I'm looking forward to his account when he gets well enough to jot it down, BTW.)

In any case, rbdave is not only an experienced RB diver and cave diver (you've done a few sumps, haven't you, Dave?) but also a guy I'd like to have around if I ever had an accident ... his EAR helped save the Inspiration diver's life two weeks ago ... :thumb:

I remain concerned that dilution hypoxia is a common phenomenon with all kinds of rebreathers, Could you expand on this, Paul? Not quite sure what you mean ... hypoxia in rebreathers is quite easily monitored ...
It would seem we still have a lot to learn about the physiology of rebreather diving. Maybe still some issues, yes. But a lot is actually well-known. It's when this knowledge is not properly taught, learned and mastered that the problems appear. Often the basic rules are ignored ...
when combined with solo diving - another common rebreather practice - this can be fatal. On this I agree entirely. The Queensland accident, the Sydney accident (MK15.5), the recent Norwegian Navy accident (SIVA 55), the Stockholm accident last year (Azimuth) all had happy endings because the divers essentially were not diving solo. This is not an anti-solo diving rant in general. For OC, it may have it's uses in certain circumstances (e.g. cave exploration, photography). But it does seem to increase the fatality rates for RB diving ...

[The Iceni]

fins wake once bubbled...
Could you expand on this, Paul? Not quite sure what you mean ... hypoxia in rebreathers is quite easily monitored . . . . . It's when this knowledge is not properly taught, learned and mastered that the problems appear. Quite so! I am just concerned that I read of so many near misses with RBs. The fact that some appear to consider it is safe to RB solo without a O2 monitor begars belief.

[saturated]

I think all rebreathers should come in a box that says "brain not included". Diving solo is risky, diving solo with no way of knowing your ppo2 is just plain dumb. You my friend have been lucky. While I wont say I have never dove alone, I will say that whenever practical I have a buddy. When I do dive alone redudancy is the key, and checking my ppo2 every couple minutes is the zone. There are to many new Breather guys reading this board to advocate being reckless. Why not at least have an oxygauge. Case point, what if you are at 100', you have an emergency and need to ascend quickly. (Your left foot was just bitten and is bleeding). In all the confusion you forget that you have breathed your po2 down to .7. You begin your ascent. Now your po2 is dropping rapidly. You have no audible alarms, or gauges, so you dont know your po2. The emergency has gotten your brain focused on getting out of the water. At 50 ft your po2 is below life sustaining. As you hit the surface you are unconsious. The dive boat is 500' away picking up other divers. You may die on the surface from either drowning or hypoxia if the mouthpeice stays intact. Of course had you had a simple oxygauge and had the habit of watching it, you would have seen the problem as it progressed and probably lived to tell about it.

Sorry to get like this, but what we believe to be a similiar incident happened to a friend of mine in 86. We all have the It wont happen to me syndrom, that is exactly what kills people. If you dive blind, it is my personal belief and experience that at some point it will catch up to you.

For the sake of those that care about you, get a gauge and a buddy.

[caveseeker7]

Dr Paul Thomas once bubbled...
Quite so! I am just concerned that I read of so many near misses with RBs. The fact that some appear to consider it is safe to RB solo without a O2 monitor begars belief.

All eCCRs have them (and need to to get the mix), usually three sensors and two displays. The biggest problem ought to be cmf SCRs as you simply don't know exactly what you're breathing. And as I mentioned above, I can't believe that any of their manufacturers make O2 monitoring optional if available at all. And that divers use them without ... by the time they get through their training they ought to know better.

[rbdave]

Hi Saturated,

The homebuilt is long gone ( and had triple 02 sensors by the time it was replaced )

I now dive an Inspiration which has good 02 monitoring and I'm careful to check it.

Cheers

Dave

Gee, I hope nonbody bites my foot when I have 3 hours deco to go. :)

[fins wake]

Gee, I hope nonbody bites my foot when I have 3 hours deco to go. Isn't Oz the place where you have to check under toilet seats for giant redbacks before you take a big one? And where the snakes are arguably less charming than the one in Harry Potter II? :D

[saturated]

Inspiration, way to go!

Sorry just do'nt want to see anyone hurt themselves needlessly.

congrats and welcome to the turtle family. Enjoy!

PS: Cary a turnicate.

[rbdave]

Hi Fins Wake,

Sure theirs plenty of stuff to bite you on land but I've only ever been biten underwater.

As part of my very slow learning curve I no longer pull sharks tails.

I was biten on the wrist once and it bled quite a lot. It was nearly very serious as my dive buddy nearly drowned cause he was laughing so much :)

Cheers

Dave

[Tigerscuba]

hey saturated,

Thats Tommy your speaking of of is'nt it? If I remember right it was has achilles tendon that was ripped out. That one kind of stuck with me to.

I remember the chamber rides as well. I do think it would be a good idea if you have'nt experienced hypoxia, hyperoxia to do it under controlled conditions. It will indeed show you how suddenly it manifests itself. Some people do show effects prior to black out. I myself felt very disoriented for a brief "tick" prior to black out. Definately not enough time to bail out though.

Saturated, love the profile pick!

[BigJetDriver]

saturated once bubbled...
I think all rebreathers should come in a box that says "brain not included". Diving solo is risky, diving solo with no way of knowing your ppo2 is just plain dumb. You my friend have been lucky. There are too many new Breather guys reading this board to advocate being reckless. Why not at least have an oxygauge?

Case in point, what if you are at 100', you have an emergency and need to ascend quickly. (Your left foot was just bitten and is bleeding). In all the confusion you forget that you have breathed your po2 down to .7. You begin your ascent. Now your po2 is dropping rapidly. You have no audible alarms, or gauges, so you dont know your po2. The emergency has gotten your brain focused on getting out of the water. At 50 ft your po2 is below life sustaining. As you hit the surface you are unconsious. The dive boat is 500' away picking up other divers. You may die on the surface from either drowning or hypoxia if the mouthpeice stays intact. Of course had you had a simple oxygauge and had the habit of watching it, you would have seen the problem as it progressed and probably lived to tell about it.

Sorry to get like this, but what we believe to be a similiar incident happened to a friend of mine in 86. We all have the "It wont happen to me syndrome", and that is exactly what kills people. If you dive blind, it is my personal belief and experience that at some point it will catch up to you.

For the sake of those who care about you, get a gauge and a buddy.

AMEN, BROTHER, AMEN!!!

THIS POST WAS DEFINITELY WORTH REPEATING!!!:shout: