Water in regulator at depth causing panic

[johndiver999]

No, just walking around. I was refuting @glc's claim of about a minute of consciousness yielded from those three breaths. Several small breaths circumvented the urge to breath that would have been present if I had just held a large breath (3x normal), somewhat simulating the lessening of the need to breath during an ascent.

so you are reporting that you survived breathing 3 breaths in a 90 second period while walking?

 

[inquis]

Exactly. The claim, as I understood it, was I would pass out around 60 s.

 

[Raphus]

I am not sure this is correct. I’m no physiologist, but human lung is not a rigid tank, it’s a bag (Captain Obvious mode on). So, even after a full exhalation, whatever residual volume of gas in the lungs remains, its pressure is equal to the ambient – in your example, 4 ATA at 30m. With air, that’s 0.84 PPO2, your starting point

My example is about breath holding/cesa.
Reading all the responses, maybe I didn't write this clear enough.

Of course for a ppo2 of 0.2 at 4atm it's not air. So i's ether a hypoxic mix, or one breath, where oxygen is already used up.

 

[berndo]

My example is about breath holding/cesa.
Reading all the responses, maybe I didn't write this clear enough.

Of course for a ppo2 of 0.2 at 4atm it's not air. So i's ether a hypoxic mix, or one breath, where oxygen is already used up.

You must have mixed up something here. The numbers don't make sense for any kind of swimming ascent. What gas would you be breathing at 30m that leaves you with 0.2 in you lungs?

 

[kissonerga.ccr]

My example is about breath holding/cesa.
Reading all the responses, maybe I didn't write this clear enough.

Of course for a ppo2 of 0.2 at 4atm it's not air. So i's ether a hypoxic mix, or one breath, where oxygen is already used up.

Ok, but my point is that at depth of 30m even after full exhalation, your PPO2 in the residual lung volume is not reduced to 0.2. On the surface, the difference between PPO2 in inhaled and exhaled air is about 5% – roughly speaking, from .21 to .15-.16 – that’s equivalent to the amount of oxygen metabolized and converted to CO2 (which suggests that PP CO2 in exhaled air on the surface should be about the same, i.e. .05). On open circuit, on every inhalation cycle, PPO2 of the gas in your lungs is restored to the FO2 of the gas in your tank times ambient pressure in bars. On air, that‘s .21 x 4 = .84. Gas exchange between ‘normal’ inhale and exhale can only reduce it by the same 0.05 at best – and you vent this CO2 with your exhalation. Then the starting PPO2 for your ascent is about 0.80 at worst. OK, that’s in a small volume of ‘deflated’ post-exhalation lungs, and whether it’s enough to cover your metabolic needs during the ascent would require a different calculation, assumptions would have to be made about your MET load, body weight, etc.

Incidentally, if we assume that on full exhalation we indeed went from total volume of 6 liters to residual 1.5L, i.e. 4x reduction, then on ascent from 30m, with 4x of gas expansion, at the surface we would be exactly back to the TLC, without the need to vent, and no / minimum risk of lung rapture. Could this be the reason for why submariners in training are told to fully exhale prior to the ascent (as described by @boulderjohn in #94)?

All of the above is strictly IMHO, and in no way suggesting that CESA should actually be performed without venting – what if we start with more gas in the lungs? The neat coincidence of expansion multiples in the example above is just that, a coincidence

 

[lowwall]

This still does not add a lot. After a full exhale, about 1200 ml of gas remains in your lungs.

I just wanted to note that the 1200 cc residual volume is after a deliberate maximum exhale. It's uncomfortable to empty your lungs to that extent and most people never do it.

The difference between that minimum and the amount of gas left after a normal exhalation is called the "expiratory reserve". It's around 1100cc in an average human male. Which means you will have around 2300cc of gas in your lungs at the end of a normal exhale.

 

[Wibble]

... Could this be the reason for why submariners in training are told to fully exhale prior to the ascent (as described by @boulderjohn in #94)?

When a submariner's in their suit and launched out of the escape hatch, they're literally hurtling to the surface and shoot out of the water. It seems logical to get them to start with their lungs empty as it will quickly fill during the very fast ascent.

 

[GJC]

I think he did that in the early 90s with no hood. Swim up to the surface and live or don't do the training and become a bosons mate. His explanation was that it proved they could do it from normal operating depth without any assistance if needed.

I learned a little more about submaine escape.

Ascent rates are over 400 ft/min. (So not breathing from 150 ft is not that difficult).

The difficult part is the rapid compression from the 1 atmosphere pressure inside the sub to the ambient depth pressure and then the rapid pressure reduction from depth to surface. I can imagine a substatial number of injuries to lungs, ears and sinuses now matter how well the trainees are prepared.

 

[bcaderunr]

Here's a photo of the sub escape tank that the Navy uses. 60' deep. Training is voluntary and participants can drop out without penalty at any time.

 

[L13]

I learned a little more about submaine escape.

Ascent rates are over 400 ft/min. (So holding your breath from 150 ft is not that difficult).

The difficult part is the rapid compression from the 1 atmosphere pressure inside the sub to the ambient depth pressure and then the rapid pressure reduction from depth to surface. I can imagine a substatial number of injuries to lungs, ears and sinuses now matter how well the trainees are prepared.

I was on submarines (US) in the early 90's. We did not have to do an actual ascent from depth as part of our qualifications. We were told that ascents from 600ft were survivable. ascents from 200ft almost guaranteed injury, and ascents from shallower still had significant risk. We drilled the procedure through start of ascent, but not the actual ascent. There were strict instructions not to hold your breath.

Actually, most of the time on our submarine, internal pressure was the equivalent of 5,000 to 10,000 feet (less than 1 ATA) if we had been submerged for any length of time.

EDIT:
Given where submarines operate, either the water is way deeper than 600ft, or the US government doesn't want anyone to know you were there. In either case, you will be rescued by a DSRV if you aren't dead or going to die. The escape trunk is there for emotional reasons, not practical ones.