Water in regulator at depth causing panic

[kissonerga.ccr]

Example: 30m depth. Po2 of 0.21 which is the equivalent to the po2 we have at the surface.
You ascent to 10m. Your po2 is now half. So around 0.1, which is too low. You will probably fall asleep and never reach the surface.
But you could stay at 30m for a bit longer. Because of the higher po2.

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

 

[GJC]

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

 

[lowwall]

Example: 30m depth. Po2 of 0.21 which is the equivalent to the po2 we have at the surface.
You ascent to 10m. Your po2 is now half. So around 0.1, which is too low. You will probably fall asleep and never reach the surface.

True, but not really relevant to anyone except deep technical divers. A PPO2 of .21 at 30m means the tank was filled with a hypoxic mix of only 5.25% O2.

Since your regulator delivers your gas at the ambient pressure, if your tank is filled with air (21% O2 which equals a PPO2 of .21 at 1 atmosphere), then you will be breathing gas with a PPO2 of .84 at 30m (.21 x 4 atmospheres). Which means you've got plenty of O2 molecules in your blood and tissues to perform the work needed to get you to the surface in a CESA.

 

[boulderjohn]

Remember I wasn’t operating from a full lung of air. More like 1/4 or less, whatever the residual volume is after a normal exhale.

Navy submariners are taught to exhale fully before beginning their ascent and then continue to exhale as they ascend.

I have been crusading on this issue for a very long time. The way we teach CESA makes students believe they won't make it, so they hold their breath, and statistics show that an air embolism following a panicked ascent to the surface is the number one non-health related cause of scuba fatalities.

 

[GJC]

Which means you've got plenty of O2 molecules in your blood and tissues to perform the work needed to get you to the surface in a CESA.

That's not quite right.

97% of the oxygen in your body is carried by hemoglobin. Unless you increase your hemoglobin, the rest of the oxygen in your body (the 3% that is dissolved in liquids and tissues) increases only a little bit relative to the total. The dissolved part gets metabolized and used up really fast and is then replaced from the oxygen bound to hemoglobin. So even under pressure, and even if breathing 100% oxygen, you still only get about 5-10 min before all the oxygen is used up and cells start dying after you stop breathing. (This doesn't mean you get to stay awake the whole 5-10 min though)

 

[inquis]

I'm pretty sure "... and tissues" in @lowwall 's quote includes the lungs, from which the hemoglobin can grab more O2.

 

[GJC]

I'm pretty sure "... and tissues" in @lowwall 's quote includes the lungs, from which the hemoglobin can grab more O2.

This still does not add a lot. After a full exhale, about 1200 ml of gas remains in your lungs. This expands to 4800 ml ascending from 4 atmospheres. Yes you do get the equivalent of a several breaths as you ascend, but that's still less than a minute of normal breathing on the surface at rest. So this can add maybe another minute of useful consciousness.

If your regulator still works but your tank is empty at depth. You will be able to breath from it as ambient pressure drops. You can get a lot of breaths from it on the way up if you need to and you don't ascend too fast.

 

[boulderjohn]

I

This still does not add a lot. After a full exhale, about 1200 ml of gas remains in your lungs. This expands to 4800 ml ascending from 4 atmospheres. Yes you do get the equivalent of a several breaths as you ascend, but that's still less than a minute of normal breathing on the surface at rest. So this can add maybe another minute of useful consciousness.

If your regulator still works but your tank is empty at depth. You will be able to breath from it as ambient pressure drops. You can get a lot of breaths from it on the way up if you need to and you don't ascend too fast.

So how is it that all those Navy submariners are able to get to the surface alive? Or are you saying that it is a fake--they really all died on the way up and the Navy is covering it up?

 

[boulderjohn]

Forget it

 

[Boarderguy]

So how is it that all those Navy submariners are able to get to the surface alive? Or are you saying that it is a fake--they really all died on the way up and the Navy is covering it up?

I work with one and one of the first things he asked when he found out I dive is how deep I've been. That was followed up by how in sub school they had to free ascend from 150 ft to gain their NEC.