Lung overexpansion

[dberry]

Hi dberry,

To review, 1 atm=760 torr/14.7 psi.

It takes a surprisingly small pressure differential between the inside and the outside of the lung to cause an overexpansion injury. The tissue surrounding alveoli can rupture with only a 77.6 torr/1.5 psi rise in internal pressure.

Regards,

DocVikingo

Yup, I work with pressure in torr and atm all the time, and have seen plenty of spectacular failures at "only" 1-2 atm. Some of the worst have been failures under vacuum (neg 1 atm). My question was prompted by a gut feeling that a medicine bottle (heavy rubber) would require a lot more than 0.1 atm above ambient to burst. I was surprised that stunt didn't damage the guy's lungs. So maybe I'm overestimating the bursting pressure of the bottle?

In my younger and more reckless days we used to pack a short length surgical tubing with dry ice and wire both ends shut. The noise when it burst was incredible (especially indoors). Our rough calculations suggested the rubber tubing withstood a pressure >1.5 atm before bursting. We considered it relatively harmless, until the wired end nailed someone in the forehead - good thing he was wearing safety glasses. Leaving a dry-ice balloon inside a mate's desk drawer is still a form of entertainment for some grad students. :evil2:

-Don (who is not condoning pranks involving unexpected loud noises or over-pressurizing anything.)

 

[Duke Dive Medicine]

I'm stealing that.

 

[Rick Murchison]

Hokay... there seems to be a fundamental misunderstanding of the mechanics of blowing things (balloons, medicine bottles, etc) up and lung overpressure. When we blow something up the pressure is applied by the muscles around the lungs, and is not a differential (overpressure) in the lungs - that is, the pressure, though greater than ambient, is still equal on either side of the alveolar sac, so there is no overpressure present. That's not to say you can't get your lungs overpressurized - all you have to do is use your mouth to pump more air into the lungs after you've inhaled as much as you can - especially if one does this multiple times, closing the glottis between each mouthful, one can create enough overpressure in the lung to be problematic. Also, spasmotic muscle contractions (coughing fit, violent sneeze) that apply pressure to the chest cavity irregularly can create areas of momentary overpressure. But blowing up a balloon? Nah
Rick

 

[dberry]

Rick Murchison has put my mind at rest about blowing up medicine bottles. And I promise to always keep my airways open while ascending!

I realize the damage would be internal, and it's not really funny, but that scene from Monty Python's Meaning of Life with the guy exploding after dinner just popped into my head... ow, I hate when that happens!
-Don