Hypoxia & Hyperoxia

Deep Thought

I have seen several cases of low and high oxygen exposure and have some personal insights including recent events. I would like to submit a couple of the more relevant experiences as learning examples.



From the most memorable event of hypoxia to most recent; several years ago when the Nautilus Explorer was running Pseudo Tech CCR trips to Vancouver BC, I was fortunate to witness Dr. Grant demonstrating a surface hypoxic event on his CCR. The premise was a controlled experiment with Dr. Grant submitting himself as the subject, with a finger sensor to monitor blood oxygen saturation and pulse while going hypoxic on the rebreather. With a group of about a dozen onlookers, Greg proceeded to go hypoxic and it was startling to see how he went from conscious to slumping over. I do not recall the exact blood saturation, however to generalize the condition is to say that his blood oxygen dropped but not significantly while his pulse rate skyrocketed prior to going unconscious. The point he wanted to make was that there were no reliable signs or symptoms of hypoxia – down you go! This experiment was repeated by Grant on a subsequent NE trip, so others may recall a similar event.



The next event in time was a ccr trip to Cocos with a new ccr diver that had a failed solenoid stuck open. The diver was aside me at about 130 feet, watching for hammerhead sharks, when I noticed the diver burping gas out of the loop. The diver has been experiencing Po2 spikes earlier on but attributed the spikes on the crash descents to get deep and away from the extreme surge. I check the display and saw 2.5 , 2.5 , 2.5 and we were on bottom for several minutes before I noticed the mouth venting. Assuming that the display was maxed out, the PO2 was likely equal to the depth in atmospheres! Oxygen was shut down, loop flushed and dive ended controlling oxygen cylinder valve. The diver showed no signs of excessive oxygen exposure.



The same diver had remedial training in my pool after the Cocos trip and experienced hypoxia. The diver, who has good open circuit skills and open circuit habits, omitted the golden rule of pre-breath and monitoring the display, we were in the pool after all. Within only a few minutes the diver started dog paddling from the deep end of the pool toward the shallow end. I have numerous open circuit Trimix dives with this diver and dog paddling is not one of their strokes. I looked into the divers eyes to see them rolled back; the divers cheeks were puffing in and out showing difficulty in breathing, while the loop still in the divers mouth. I scooped the diver out of the water, took the loop out and checked the PO2; .12 , .10 , .14 and moments later the diver was responsive on the pool deck showing no signs of distress. After a brief heart attack on my part, I took this example and compared it to the Grant hypoxia event and concluded that in this last case the diver knew that something wasn’t correct and was following survival instincts to go to the surface. The subtle signs that told this diver to follow their instincts would not have saved their life as we know that surfacing means lowering the PO2, but none the less the instinct was there. In this case the oxygen was turned on, the cylinder was full, the injector line appeared connected yet was not engaged fully. Follow proper pre dive skills.



My personal event not long ago was a hypoxic event that occurred on the surface during a pre-breath. I was doing a shore entry with a fellow diver, when my pre-breath was interrupted by a park ranger who was doing site checks. I got to yakking with the official, doing my best job of politicking then proceeded to put my loop in. In the mean time the electronics went to sleep, I resumed pre breath and walked the few paces to the shoreline where I bent over to pick up my fins. Whoa, dizzy, something is not right….oh electronics are off, turn them on and they displayed PO2’s in the low- low digits! Interuptions happen, never take your eyes off the ball...



Now I have a couple dives under my belt, and have had things happen as do when you engage in any activity long enough. If you call yourself experienced you have probably had a few experiences. If you learn from mistakes, you can go on, if you do not learn you will most likely die on a rebreather.



Chances are that you will not be given any reliable signs or symptoms of either high or low oxygen so you must stay diligent to monitor your PO2, or you will find that little mistakes can have grave consequences.



I submit these as examples to learn from and seek no criticism from divers who get most of their experience from their computer keyboard. If you have had similar or unique experiences, I would ask that you submit them for the education of all ccr divers.



Ron

silentscuba

Great post Ron- This is the type of information that we can all learn and benefit from. I hope more will follow.

Sincerely,

Curt

__________________
Curt McNamee
rEvo CCR Diver
KISS CCR Diver
www.silentscuba.com

caveseeker7

Thanks for sharing those incidents, Ron.
Very nice going on the Cocos dive.

Would be intresting to get the numbers for the two experiments from Dr Grant.

__________________
Cheers
Stefan



"Political Correctness is a doctrine, fostered by a delusional, illogical minority,
and rabidly promoted by an unscrupulous mainstream media,
which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.!"

scubagrunt

jondive

After a year on SCR I have my first dives this Sunday on my Kiss. This has been a great reminder to 'do the basics' and 'don't take my eye off the ball'

Thanks

jhaaja

I have the near fatal O2-convulsion incident. You can read about it from its on thread.

On OC I had one slight hypoxia case. We were doing a deep dive and during the last stop at 6m we did back gas breaks from O2. On the first break I switched to back gas TX10/70. After maybe 1-2mins I started to notice that my heartrate started to climb and breathing cycle got faster. Then I realized that the gas did not have enough O2 for me. I swiched to TX20/35 insted. My buddy did all his breaks on TX10/70 and had no problems.

At that time ppO2 of 0,16 just was not enough.

JH
Finland