Why is inhaling while ascending safe, if breathing holding will cause lung over expansion?

[Nitrox_DiverNY]

hi all I had a question about inhalation while ascending,

If ascending at a safe conservative rate say 10-20fpm why does the act of inhalation of breathing gas no pose a risk of lung over expansion injury?

It is the slow ascent that basically rules out a LOP injury, or is it because your airway is open even if you are rising in the water column while breathing in?

Is it safe to breath in while ascending (given a safe ascent rate below 30fpm) or will this cause any issues?



I hope my question made sense, as a relatively new diver if anyone could offer any more clarity of this question that would be great!. Thanks and safe diving to all!

 

[Cthippo]

The key is to not retain gas in your lungs as you ascend. So long as you exhale regularly after each breath and maintain a reasonable ascent rate you are not keeping the gas in your lungs where it can expand.

 

[Rollin Bonz]

An open airway is the key. An open airway allows easy pressure equalization, regardless of the respiratory phase. Your inhalation phase will likely be shortened, due to lung expansion as you ascend.

 

[tursiops]

The key is to not retain gas in your lungs as you ascend. So long as you exhale regularly after each breath and maintain a reasonable ascent rate you are not keeping the gas in your lungs where it can expand.

This, plus while you are breathing normally, in-and-out, your lungs are never shut off from being allowed to have gas escape from them as it expands.

 

[Vicko]

While breathing normally you will simply start exhaling when your lungs get full, so the gas expansion becomes a part of normal respiration.

 

[tbone1004]

hi all I had a question about inhalation while ascending,

If ascending at a safe conservative rate say 10-20fpm why does the act of inhalation of breathing gas no pose a risk of lung over expansion injury?

It is the slow ascent that basically rules out a LOP injury, or is it because your airway is open even if you are rising in the water column while breathing in?

Is it safe to breath in while ascending (given a safe ascent rate below 30fpm) or will this cause any issues?



I hope my question made sense, as a relatively new diver if anyone could offer any more clarity of this question that would be great!. Thanks and safe diving to all!

So the reason we say never hold your breath on scuba is because it's the easy way to prevent an issue.
Physiologically there is a HUGE difference between "holding your breath" and "not actively breathing". That difference is whether or not the epiglottis is open or closed.
When you take a breath in and are asked to "hold your breath", if you pay attention to your throat you can actually feel when you stop inhaling when the epiglottis closes. The reason this matters is that the epiglottis can hold back a higher pressure than the lungs can withstand. I.e. the lungs are the weak link in the chain and if you are "holding your breath" with the epiglottis closed the lungs will burst before the epiglottis lets go.
When you are actively inhaling or exhaling, the epiglottis is open and as long as it is open it is highly unlikely for you to be able to suffer a lung over expansion injury. I suppose it is possible but you would have to do something pretty egregious so it is highly implausible. The same applies to when you "pause breathing", so long as the epiglottis is open, there won't be a differential pressure between your lungs and your open air cavities *sinus, mouth, nose, etc. that can equalize with ambient pressure*.

 

[Nitrox_DiverNY]

An open airway is the key. An open airway allows easy pressure equalization, regardless of the respiratory phase. Your inhalation phase will likely be shortened, due to lung expansion as you ascend.

thanks, and very interesting. so regardless if your lungs are full of air, the pressure will force the excess air out as long as your airway is open

 

[Nitrox_DiverNY]

This, plus while you are breathing normally, in-and-out, your lungs are never shut off from being allowed to have gas escape from them as it expands.

is having a brief pause after inhalation considered to be breath holding in this situation? or should it inhale in and then right back out ?

 

[tursiops]

is having a brief pause after inhalation considered to be breath holding in this situation? or should it inhale in and then right back out ?

See post #6.

 

[RobPNW]

is having a brief pause after inhalation considered to be breath holding in this situation? or should it inhale in and then right back out ?

I find myself "pausing" but not holding semi frequently to make minor adjustments in my buoyancy near obstacles without getting inflator happy.