Physics of diving with a "straw"

[KeithG]

An interesting link: http://www.personal.psu.edu/ref7/apparatus/2003 competition/deardorff-LC.htm

Skip the stuff at the top and scroll down a bit.
Discoveries learned from this device:
· Typical lung pressure ~ 1 m water = 74 mm Hg = 9.8 kPa = 0.097 atm
· The maximum lung pressure of about 1 m of water explains why breathing under water (even with SCUBA gear) is difficult for depths greater than a couple of meters.
· Even Superman could not drink from a straw that is taller than 10.3 m since this is the maximum height of a column of water supported by 1 atm and a perfect vacuum.
· The gauge pressure inside a 9” latex balloon is approximately 20 cm of water (0.02 atm), and is roughly independent of the balloon’s diameter except for the initial inflation. This manometer could be used in an experiment where student take measurements to examine the pressure as a function of diameter.

 

[scagrotto]

The maximum lung pressure of about 1 m of water ...

That's all well and good, but inhaling and exhaling are different things. Both may use the diaphragm, but they also use the internal and external intercostal muscles in opposition to one another. Perhaps they have roughly equal strength in most people, but I'm curious if the typical maximum exhalation force that a person can exert correlates well, and equally, to their ability to inhale.

Some people have trouble blowing up a standard balloon, while others can blow up hot water bottles. A bit of googling turns up links claiming some impossibly high values for the required pressure, including "as much as a truck tire", 170 psi, and even "600 pounds of air pressure". I'll settle on the conservative claims in this article:
Jemal Tkeshelashvili - The Man Who Blows Up Hot Water Bottles with His Nose | Oddity Central - Collecting Oddities
that it takes "at least three times the pressure normal human beings are capable of."

Maybe those people can drink through a longer straw than the rest of us, but I'm guessing their ability to exhale exceeds their ability to inhale by a significant margin. Maybe most of us are closer to symmetrical, but my gut says it's normal to generate a lot more force while exhaling.

 

[BRT]

your hose will collapse probably a few feet from the surface. there is no equal air pressure to counter the water pressure.

That depends on the reinforcing of the hose, but your lungs will collapse if they are on the low end of the hose.