Lung barotrauma risk

[The Chairman]

I don't think people usually practice that.

They don't and this is an important skill to master. Anatomically, it's called the epiglottis and you'll feel it when you clear your throat. The glottis must remain open at all times, even if you pause breathing. Not sure? Make any vowel sound when you're not breathing in and you can be sure your glottis is open. A soft, soft continuous "uh" is all you need. Once you get it down, feel free to drop the vocals!

 

[TMHeimer]

The air in your lungs will force it's way out your mouth, the same way it will if you are breathing normally to never hold your breath.

I learned the trick when I was young, learning to swim and snorkel.


Bob

Thanks Bob--that's what I figured. Please explain exactly what aspect of snorkeling/swimming you were doing where you had your epiglottis open but were holding your breath. How did you happen to learn about this "trick" back then?

 

[The Chairman]

Your pleural cavity (where the lungs sit) can be acted on by several sets of muscles, but mostly the intercostal levators, scalenes and your diaphragm are used. You can "pause" your breathing at any point by 'freezing' these muscles in place without obstructing your epiglottis. These same muscles allow you to operate out of the normal range of breathing such as taking a 'super breath' to begin your ascent, as well as an extreme exhalation in order to begin a descent or to calm yourself down when you feel you're hyperventilating.

 

[The Chairman]

A good couch exercise:

• Take a normal breath
• Inhale a bit more
  • You should never feel or hear your glottis obstructing air when you inhale or exhale
• Hold for ten or so seconds
• Allow all your chest muscles to relax
  • This is a normal 'exhale'
• Force more air out of your lungs
  • More
  • More
  • More
• Hold that for ten or so seconds
• Breathe normally (recover)
• Repeat as you see fit
  • Don't hyperventilate
  • Don't overdo it
  • Stop if you feel any weirdness
  • Play with glottal sounds like a gentle cough, saying ugh-ugh, making an English style glottal stop and so forth

 

[Bob DBF]

How did you happen to learn about this "trick" back then?

I was getting water up my nose when swimming underwater. My mom explained how to use my lungs to "blow a bubble" in my nose, without exhaling, and control it as depth/pressure varied. You can't do this with your epiglottis closed.


Bob

 

[dmaziuk]

I was getting water up my nose when swimming underwater. My mom explained how to use my lungs to "blow a bubble" in my nose, without exhaling, and control it as depth/pressure varied.

Flip turns. Unless you can keep a little back-pressure in your nose when you push off the wall face-up, you're getting chlorinated water all the way into your sinuses. It stings, and everything stinks like vinegar for the next five minutes.

On the other hand you get used to water up your nose. Mask replacement drills are no problem.

On the gripping hand I keep running into rental regs that freeflow into my mask at the top of the inhale, with both epiglottis and soft palate open. On the last trip I even had to ask the shop to detune the one they gave me (instead they gave me another one that turned out to be tolerable). (I wonder if a detuned reg is a solution to @Marie13's problems with leaking masks and bubble head too.)

 

[Bob DBF]

(I wonder if a detuned reg is a solution to @Marie13's problems with leaking masks and bubble head too.)

It could be, although the list of other possible issues is quite long.

I got used to regs back when WOB was not on the radar, and the venturi effect was not yet used in regulators so I'm not as picky as some about needing high performance regs, they just have to work. I don't need an underwater C PAP machine.


Bob

 

[TMHeimer]

I was getting water up my nose when swimming underwater. My mom explained how to use my lungs to "blow a bubble" in my nose, without exhaling, and control it as depth/pressure varied. You can't do this with your epiglottis closed.


Bob

I see what your saying. Also have heard before what dmaziuk said about water getting into sinuses even with your airway closed if you're pretty much facing the surface (and have no mask on of course).
I have also heard and read of instructors advising students to blow out through the nose a bit to prevent water from getting in. I presume this advice is to keep a maskless diver from getting water in the nostrils as well, since I would think it is an extreme rarity for a diver to be maskless AND facing the surface. I always wonder why the advice isn't just to close the airway and ignore water in nostrils that won't hurt you.

 

[Bob DBF]

I always wonder why the advice isn't just to close the airway and ignore water in nostrils that won't hurt you.

Same as someone who runs out of gas, panics, and bolts for the surface; they have reached their limit, and logic is not working any longer. Advice, and talk in general, is no substitute for experience and drill. At times when tshtf that I'm glad my mentor was an Ahole.

I believe waterboarding works on the same principles.


Bob

 

[doctormike]

A few things.

1) The epiglottis has nothing to do with closing the airway. It's a tissue flap that helps prevent aspiration of food and saliva, but a minor player. It's possible to learn techniques to swallow without it (such as with people who have had the supraglottic larynx removed for cancer). It occasionally can cause minor airway obstruction on inhalation in babies because it is soft and floppy in the first year of life, and curled on itself (laryngomalacia). This is rarely seen in adults, and usually only in patients with neurological disease.

2)The vocal cords (glottis) coming together (adduction) is what makes an airtight seal of the airway. From an evolutionary point of view, that's why we have a larynx to begin with - speech is a later benefit. Because non-cetacean mammals have crossed air and food passages, we need some fancy reflexes to shut the vocal cords and keep us from drowning in our own saliva, or every time we take a drink of water.

3) Forcefully adducting the vocal cords while ascending is what causes pulmonary barotrauma. If you aren't doing that, but are just pausing breathing, then the expanding gas in your lungs will vent on ascent.

4) Getting back to the OP, my understanding of "surge" is that the volume of water that you are suspended in is moving up and down. Therefore, surge should not change your actual depth at all, and you should be at no risk of barotrauma. There are stories of people doing deco in heavy seas, where the waves were big enough so that divers at their shallow stop could actually be seen at deck level, but inside a wave adjacent to the trough that the boat was in! Not sure if that is apocryphal, but you get the point...