Do you really have to exhale while ascending?

[NJMike]

Okay, I know the question seems to have an obvious answer, but...

I just read an article from the "Lessons For Life" section on scubadiving.com.

The article is about a diver who surfaced from 6' (six feet) without exhaling and suffered an arterial gas embolism.

Six feet. That's not much. And it got me thinking about my own (still inexperienced) ascents. On the few dives that I've done, I realize that I control my breathing to help bouyancy, and this includes on the ascents.

Now I can't help but wonder how easy it would be to "control my bouyancy through breathing technique" in such a way that I pause after inhaling...while continuing to ascend...

If the ascent rate is 30 fpm, and you pause for 2 seconds, you only ascend 1 foot. That doesn't sound too bad. Even at 60 fpm, you only ascend 2'.

Back to the article...question: if you ascend 6' while holding your breath, from 60' to 54', is this the same thing as ascending from 6' to the surface?

Or is it NOT the same, because the change in pressure is greater from 6' to 0' than it is from 60' to 54'?

Is the lesson here that we need to be even more cautious about the ascent rate when near the surface...like ascending from the safety stop?

 

[Tobagoman]

There is a greater pressure change in the 1st 33 fsw. Think about it, your doubling the total pressure by diving to 33 fsw. You would have to dive to 99 fsw before you would again double the total pressure.

I'm trying to understand the jist of your question(s). As you know you don't have to exhale continuously on accent, but breath normally to avoid a lung overexpansion injury. Breath holding while accending after breathing at depth is like playing Russian Roulette, do you want to take that chance? You may only be doing it for a few feet of accension, but $hit happens and if your bouyency control gets away from you or you are distracted and accend quicker/further than you had planned while you are holding your breath an LOI is a pretty good bet.

Breath naturally on your accent, control buoyancy as you accend by expelling air from your BCD and you should be fine.

 

[ReefGuy]

Or is it NOT the same, because the change in pressure is greater from 6' to 0' than it is from 60' to 54'?

Is the lesson here that we need to be even more cautious about the ascent rate when near the surface...like ascending from the safety stop?

Bingo! Give that person a cigar.

There's nothing wrong with pausing in your breathing, just make sure to keep your throat open.

 

[genxweb]

not being as freshed up as I should be on this subject I do not think that 2 second pause will hurt you though anything is possiable. The person in the article most likely held his breath the full ascent not allowing the expanding air to exit which in returned caused the arterial gas embolism. The greatest change in pressure is usally with in the first atmosphere which would make me believe that the 6 to the surface is more dangerous. DAN just had a article in their last issue that stressed the importance of the last 15 feet due to issues such as you just mentioned.

That is just my two cents.


EDITED: wow a few people beat me to the post.

 

[matts1w]

Good question-

A volume of air will will double from 33 feet to the surface.

Even the last 15 feet after a safety stop it is crucial to continue bretahing and never hold one's breath as the volume of air in the lungs will expand by almost 1/4. That is a signifigant expansion- just about the same expansion as going from 99 feet (1/4) to 33 feet (1/2).

It is not the same as going from 10 feet to the surface as it is going from 60 feet to 50feet as greater pressure makes changes in air volume smaller and more forgiving. That is why it is far easier to maintain being neutral at 50 feet than it is in ten feet.

Nonetheless...one should NEVER EVER hold one's breth while diving. Slow, continual, and relaxed. Nice breath in...slight pause....long breath out...slight pause....Nice breath in....

Hope that helps.

 

[gcbryan]

deleted:question answered while I was typing.

 

[NJMike]

It's "contra-intuitive" but from an air exhalation perspective, it seems like "the shallower the depth, the greater the danger" from not exhaling properly while ascending.

From a safety stop to surface perspective....if you are neutrally bouyant at 15', then it should be easy to fin up to the surface when the safety stop is over. I think it would also be easier to control the ascent rate by finning as opposed to adding a little air to the BC. But even with a "finning" technique, you'd still have to be releasing air from the BC.

Once the safety stop is over, I guess the attitude should be "OK, we made it this far, now let's take it nice and slow to the surface..."

 

[matts1w]

Once the safety stop is over, I guess the attitude should be "OK, we made it this far, now let's take it nice and slow to the surface..."

Exactly! That is also why it is so important to be properly weighted. Many divers have a hard time holding their shallow stop when their cylinders are around 500 psi and far more buoyant. Instead of relaxi0ng at 15 to off gas, they spend three minutes finning to keep themselves down, then cork to the surface.

 

[MXGratefulDiver]

Once the safety stop is over, I guess the attitude should be "OK, we made it this far, now let's take it nice and slow to the surface..."

That would be a nice attitude ... but the reality is something very different. From my observation, the majority of recreational divers take far too little time to surface once the safety stop is over ... often just a few seconds ... :11:

... Bob (Grateful Diver)

 

[Doc Intrepid]

Once the safety stop is over, I guess the attitude should be "OK, we made it this far, now let's take it nice and slow to the surface..."

This becomes more and more important the longer your dives are - and if you are pushing NDLs for multiple dives over multiple days it can make a critical difference. When you begin doing decompression diving your ascents can become matters of life or death.
We lost a good friend and dive buddy of ours last summer who had issues on an ascent.

As Matts just said, the goal is to be able to control your ascent all the way to the surface with nearly empty tanks - e.g. at the very end of your dive - and weight yourself accordingly, so that you are capable of doing that final 10' or so to the surface very slowly and carefully.