Doc Deep dies during dive.

[Lorenzoid]

That's because diffusion sucks out all the oxygen (there is a 100% gas gradient) from the alveoli and instantly knocks you out, like breathing any other inert gas, be it Co2, Nitrogen or Helium.
Respiration will slowly accumulate the co2 even with a bag over your head, leading to hyperventilation. In this case hypoxia happens because of extremely shallow breathing leading to no exchange of gas.

I'm obviously in over my head (ha ha) discussing physiology and respiration science. We're getting kind of off topic anyway. But thanks for the clarification.

 

[Germie]

There is nothing peaceful about hyperventilating to death.

Did you try? haha.

No, seriously, if you want to die peaceful, you need to have a way that the CO2 is not accumulating in your body. So diving a ccr with a functioning scrubber and the O2 closed will make you slowly dying. Sadly there are examples of accidents where this happened and probably the unfortunate diver did not feel it.

The PCO2 elevation in your body will give the signal to your brains, that you have to breath. So if there is not a too high PCO2, you will not feel unwell. Freedivers learn how to ignore the signal from the brain to breath again. This is not due to a lack of oxygen, but due to a too high PCO2. If you ignore that signal, you don't feel anymore that you get too less oxygen in your body. That makes freediving quite dangerous. That also makes why you have to do that with a buddy and why for example you have to move a finger in the statics breathholding.

Breathing helium from a balloon means you pass out due to a lack of oxygen, then you fall down and normally your brain get the signal again to breath in and then there is air again. So you will awake again.

I have had one more or less minor CO2 issue. At a depth of 132m I did not feel unwell directly, but I felt a little bit extra awake. I also felt that my breathing rate was double of my normal breathing rate. I could not get that into control. Decided to go up again and around 110m I was feeling complete normal again and also my breathing rate was normal again. I know for sure this was a CO2 issue. I happely never had this again, but I am aware of my breathing rates during a dive. CO2 hits in diving can mean you cannot go to bailout anymore, your breathing rate is soooo high that you will drain your tank 4-10 times faster than normal. And to loose CO2, the only way is the lungfilter and that is not working well anymore when you breathe too fast.

If you do really deep dives, and then I mean dives over 120-130m depth, it is not only the END anymore. You also have to deal with an EADD, equivalent air density depth. If you use a 6/72 diluent on a 134m deep dive, the END is 28m if oxygen is not narcotic, so within the DIR standards. The END is 33m if you state O2 is narcotic. BUT, a big big but, the EADD is 48m on ccr. That means the gas you are breathing is a thick as diving air to 48m.
If you dive OC, it is 44m for the EADD.
Doc deep went to a depth over 300m. Now just an example for a 200m dive: If a diver is using a 3/90 trimix, the MOD was 452m if you just look at the PO2. If he reached the 200m with this gas, the PO2 of his breathing gas was 0.62 which means a lot of deco (the higher the PO2 the less deco you will get, so normally you won't use only 0.7 at the bottom, but something between the 1 and 1.4). But we will ignore in this example the PO2 for deco. The END at 200m is only 8m (or 10 if O2 narcotic), so that is really low. A good gas you would say to stay clear at 200m. BUT, the BUT is already here the EADD, that is already 37m. So that is already really getting higher.
If he uses a 5/85 which has a MOD of 267m, the EADD at 200m will be already 46m.
This means it is impossible to reach 300m with not a quite high EADD, even if you would use 3/97. YOur breathing gas will be within the PO2 and END range that is 'safe', but the EADD will be higher.
But you will not use a gas without N2, as the risk of hpns increases then. So a little bit N2 is normally still left in the gas you breathe.
And even with a 1% N2, the EADD increases already a little bit.

Almost fur sure you get hpns on such dives. So your hands are working less in control then normal. But you are still clear in your head because of a right END. I have had hpns 1 time at 128 m. It was not something I worried about, it just felt strange and I was completely clear. It does not hurt. But if you have such a thing at the 200m, will this reduce your ability to stow or grab things? Probably yes. Will this also influence your stresslevel? I guess it will.

A recorddive like this means you have to go down as fast as possible. You must go down over 20m/minute. So you have to control your bouyancy. We don't know where it went wrong in the dive. But also if you do deep bouncedives, you go up the first part really fast, also with 25m per minute or a little bit more. This is done because you have to go up asap to reach the theoretically calculated offgassing point. The offgassing point is a theoretically point which is not completely safe to trust, but you need to use in such dives, it is a point that you can go up as fast as possible as there is no inert gasloading till that point that can cause problems. But remember, doing such dives is not safe, no diveplan is safe to trust, but you have to make a lot of theorically modifications also. If you go up with 10m per minute, the dive will take too long. So with a bounce you go down fast and go up fast till that theoretically point. I can tell you that getting up that fast is a strange feeling, you really have to train that. But you need to have that control also when having hpns, and maybe have accumulating CO2 levels.

Dives over 100m depth mean you have a lot of deco. On a 100m dive with 15 minutes bottomtime, 1 minute more bottomtime means about 8 minutes more decotime. But at 130m, the 1 minute more already means 22 minutes more decotime. Extrapolate this to 300m or more and only a few seconds longer at depth means 1 hour or more deco.
Is this relaxed diving? Such dives must be planned really strickt. It is not a relaxed dive, it is a dive that needs continuous action, evaluation and adapting.
Where I had to turn around on a try to reach the Bivac hall in the Ressel cave because we were around 5 minutes late, you will know here that 10 seconds late at 300m means maybe you will die.

 

[The Chairman]

A recorddive like this means you have to go down as fast as possible.

No. It means you have to magically overcome the effects of compressive arthralgia. You're worried about decompression and that's not what killed him.

 

[Nick_Radov]

Or, and this is an admittedly crazy thought...let's train to people to avoid high CO2 scenarios by using proper gas mixes, streamlined gear and trim, efficient propulsion techniques, and encourage some basic fitness levels. Oh, and I would be remiss if I didn't beat my GIVE THE PEOPLE HELIUM horse.

Sure, all good ideas. And yet when I had a problem with (I think) CO2 I was using a proper gas mix (15/55 trimix) going down the descent line at only about 100 ft, had streamlined gear, was riding a scooter, and had a fitness level higher than most tech divers. But I still got myself into a little trouble because I made some other mistakes including wasting too much time screwing around on the surface in rough conditions getting my gear squared away, and then tried to rush the descent instead of taking a moment to relax. It worked out fine in the end but if I had panicked then I could have had a real problem.

I'm not any kind of great diver but I think similar problems can creep up on anyone in the wrong circumstances.

 

[Nick_Radov]

If you use a 6/72 diluent on a 134m deep dive, the END is 28m if oxygen is not narcotic, so within the DIR standards. The END is 33m if you state O2 is narcotic.

The latest research indicates that oxygen is less narcotic than nitrogen.

Is Oxygen Narcosis A Thing?

There’s been a long running debate as to whether oxygen is a narcotic diving gas. Training agencies CMAS, GUE, PADI and PSAI include O2 in their equivalent narcotic depth (END) calculations. Others like BSAC, IANTD, NAUI and TDI do not. The problem has been reliably measuring gas narcosis. Enter...

gue.com

But I'm not interested in going to 134m to test that theory.

 

[The Chairman]

The latest research indicates that oxygen is less narcotic than nitrogen.

Is Oxygen Narcosis A Thing?

There’s been a long running debate as to whether oxygen is a narcotic diving gas. Training agencies CMAS, GUE, PADI and PSAI include O2 in their equivalent narcotic depth (END) calculations. Others like BSAC, IANTD, NAUI and TDI do not. The problem has been reliably measuring gas narcosis. Enter...

gue.com

But I'm not interested in going to 134m to test that theory.

Mainly because we metabolize O₂ so quickly.

 

[happy-diver]

Compression Arthralgia | Deep Diving Maladies

An overview of compression arthralgia | Hyperbaric deep diving malady | Compression arthralgia causes, symptoms, treatment | By Andy Davis

scubatechphilippines.com

 

[PirateFoxy]

Off topic, but we need to stop perpetuating the myth that panic attacks have something to do with someone's experience/mental "toughness"/etc. Especially in diving, physiological response to eleveated CO2 levels is usually the culprit.

I wouldn't be at all surprised if other factors have an influence on your sensitivity to the physiological response, also. Like external life stresses that have your body in a more 'primed' state to panic, that sort of thing. So you have your own personal tolerance, but then you can be more sensitive than that if your brain/body are in the state for it? And our brains can be weird so you may not even realize you're in a higher risk state until panic is triggered.

 

[Bob DBF]

Off topic, but we need to stop perpetuating the myth that panic attacks have something to do with someone's experience/mental "toughness"/etc. Especially in diving, physiological response to eleveated CO2 levels is usually the culprit.

There is a pretty direct connection between elevated CO2 and panic, however, for some it takes a little, and others a lot. That may be where the experience/mental toughness comes in. How one reacts to the initial problem is key, one can put the initial urge to panic aside and recognize the problem and work to solve the issue, or succumb to it.

My training in diving, and the military, focused on solving the problem, avoiding looking on one's impending doom. So far that has worked for me, however on several occasions, both underwater and on dry land, I could see where I could panic if I couldn't turn things around. None of which involved a bad CO2 hit, which I can recognize from personal experience.

Most everyone thinks they'll never panic, until they do. You just can't know and the "it'll never be me" syndrome is little protection when it hits.

Amen to that, I've been lucky, but not saying it can't happen to me, I've seen how close it can get.

 

[uwxplorer]

My suspicion is that panic, as we know it, is commonly induced by some combination of hypercapnia and the fight-or-flight reflex. If I'm building up CO2 in a controlled environment, I might feel safe enough that I don't panic; I might just pass out rather peacefully.

Like those pigs, I guess... (warning, graphic footage, probably representative of many a scene deep in a cave)

Pig Gas Chambers - A Look at the Most "Humane" Method To Kill Pigs