Holding your breath on ascent...

[Thalassamania]

It also depends on the depth at which the breath holding takes place. Holding ones breath between 100 and 90 feet will not have the same impact as between 20 and 10 feet. IMO

As I indicated:

4 feet to the surface is enough to do it.

 

[AlexKilpatrick]

The rubber in the balloon is stronger than your lung tissue and the muscle in your throat is strong enough to keep anything from getting into (or out of) your lungs.

Bob

Ah, ok. I hadn't thought of it that way. I was just picturing the lungs like a balloon, like in all those science fair projects. It makes sense that the lung tissue would fail before the epiglottis.

 

[MXGratefulDiver]

.....

 

[JanK]

Not long ago I posted a similar question

The answers were:

- It takes a surprisingly small pressure differential to cause a lung expansion injury. A diver well might not be aware of this differential or have any other physical indication until the lung tear has already occured.

- Indeed. Dancing furiously around the technical minutiae of ventilator therapy, it can generally be said that we aim to keep pressures (relative to ambient) below 30-35 cm/H2O (about 0.4-0.5 psi) to avoid alveolar/small airway damage (volutrauma). The threshold for major airways (barotrauma) is about 45-50 cm/H2O (about 0.6-0.7 psi).

Sobering stuff!

 

[gsk3]

Ah, ok. I hadn't thought of it that way. I was just picturing the lungs like a balloon, like in all those science fair projects. It makes sense that the lung tissue would fail before the epiglottis.

To aid gas exchange between the blood and the air spaces, alveloar walls are literally one cell thick in many places. Look at the walls labeled "inter-alveolar septum" in this light micrograph:
http://legacy.owensboro.kctcs.edu/gcaplan/anat2/notes/A83_Alveoli_TypeI&II_40X.jpg

To figure out what you're seeing, thick of it as a slice through a bunch of little tiny balloons. So those big white spaces in between are the air in the middle of the sacs, and the pink/purple cells are the cells making up the wall of the balloon.

 

[Dominantly]

4 feet to the surface is enough to do it.

I have read the same, but wonder if there is difference in the amount of air taken in at 4ft. I would think that there would be a marked difference in taking in a capacity breath, vs a normal to shallow breath and then surfacing.
4' is what like .06 difference in pressure from the surface, so a fairly small percentage of Atm change.

 

[dumpsterDiver]

I understand that under no circumstances should anyone hold their breath while ascending however it seems that there are a few posts floating around that suggest that for whatever reason this still happens. I'm not trying to blame or shake my head at these people rather my intent is to further understand what happens.

When I try to to simulate a breath hold on ascent while on dry land (by breathing in as deep as I can) I can feel my lungs expand and my chest area feels tight. I'm not about to try this under water so I was wondering if anybody knew if you would feel the same sensation if this ever happened while diving. I can only imagine that you would feel pain as your lungs over expand. Anybody have any insight on this matter? Experience or hear-say?

These are the things that keep me awake at night...

I can remember two times when I held my breath on ascent. Once was a scary rescue (I had donated my reg and literallly forgot to put another reg in my mouth while I shot for the surface with a victim, so I "naturally held my breath") and another time I was being an idiot and jumping off the bottom in 12 feet or so.

For me, both times, I began to feel discomfort and an overfilling of the lungs and at the time I had my throat locked down and I was holding my breath. I quickly let the air out and maybe had some residual discomfort and a little cough, but no other symptoms.

In general, if you are calm, ascending at a normal slow rate and you do NOT have your throat locked down (i.e., you have the air way open or relaxed) expanding air in the lungs will naturally just come out by itself I would definitey NOT recommend anyone deliberately trying to prove or disprove this idea.

I think this question come up with new divers: What if I forget to exhale? The answer for 99.99% of people is that the air should naturally come out, if you are healthy, have no obstruction, and the ascent rate is reasonable.

Basically, as long as you are calm and actively breathing there should be no problem.

 

[NIT-LVR]

How right you are Doubler......less sizeable expansion of gas.....but the habit of doing so at any depth is the no no.

 

[AlexKilpatrick]

So here is a related question.

If you hold your breath during a regular commercial flight ascent (which is up to 8'000 feet or so pressure altitude) will you have a lung over-expansion problem? I think this is physically impossible because of the time it would take, but it is an interesting question.

 

[bamamedic]

I think, that with an ascent in an aircraft, you're actually reducing the pressure in your lungs, not increasing it.