Question

You probably heard about deep-sea diving with suits in which the divers breath fluids. The movie "The Abyss" portrays it wonderfully. The diver is put into a diving suit which is filled with an oxygen-rich fluid that he can breath. After some disorientation, the diver starts to breath the fluid and can dive to depths of up to hunderds or thousands of meters. (Don't you love sci-fi?)

Still, one thing puzzles me. There's more air in a body than just in your lungs. What about all the air in the Eustachian tubes in your ears? Won't your eardrums rip when the pressure changes that much and there's still air in those tubes? And what about the gasses in your bowls or stomache? Will they dissolve or will you also need some sort of an enema when you dive to those depths? Is it vital to burp so that all the gasses in your stomache are gone? And are there any other air bubbles inside a body that usually are harmless but could seriously injure someone at those depths?

Answer 1

It is a very good film and it does seem very futuristic, but it is actually partly reality. These chemicals, these liquids do exist. They're called perfluorocarbons. They include fluorohexane for example, so a string of 6 to 8 carbon atoms with lots of flourines hanging off the side and they're very good at dissolving oxygen. So, one way of doing this would be to instil these fluids into the respiratory tract and you saturate them with the oxygen, and then you move the fluid in and out, in the same way that you would when you were breathing.

Why this is helpful is that when a person descends underwater, the pressure they feel from the surrounding water goes up and up, the deeper they go. So, you have to therefore put the gas into the lungs to keep the lungs inflated, under progressively higher and higher pressures. One consequence of this is that it drives other gases like nitrogen and things into the tissues at extremely high pressures which means that then when you decompress, those gases come out of solution in the tissues and form bubbles which can cause the bends, they can cause damage to the brain, and cause damage to bones and muscles and so on. So if you use a fluid in the lung, because fluids are incompressible then you wouldn