[♩INTRO ].

Wouldn’t it be awesome if you could just breathe underwater like a fish? It would be totally awesome...

Well, sorry to burst your bubble, but that’s not going to happen. Your lungs just aren’t up to the task of extracting oxygen from water. All right, so we can end the episode now, right?

We got the answer? Well, no. Because the fact that you can’t breathe water doesn’t mean you couldn’t breathe any liquid.

In fact, there are couple doctors trying to make liquid ventilation a thing, not to fulfill some sci-fi fantasy, but to save lives. Because of the difference in pressure your lungs feel in space or underwater, liquid ventilation could be useful while exploring the far reaches of the universe or the depths of the ocean. But more immediately, it has the potential to help those who struggle to get enough oxygen, like premature babies and people with lung injuries.

Of course, breathing a liquid isn’t as simple as channeling your inner fish. Your lungs just don’t have the surface area you’d need to extract enough oxygen from water. The air we breathe has twenty times as much, making things a lot easier.

And liquid is also a lot thicker than air, so our lungs struggle to flush it out efficiently. To get around the first problem, scientists studying liquid ventilation work with liquids made up of perfluorocarbons, or PFCs, instead of water. PFCs are specially designed hydrocarbons, or molecules made up of carbon and hydrogen, where some of the hydrogens have been replaced with fluorine.

They’re biologically inert, so they won’t harm things like your kidneys or liver. And thanks to the weak bonds between their molecules, they let plenty of gas molecules squeeze in. So they can carry three times as much oxygen as our blood, and almost forty times as much oxygen as water at room temperature.

But the part we haven’t quite figured out is that second problem: the viscosity. Since they’re thicker than gas, PFCs can’t move through the lungs fast enough to efficiently clear out carbon dioxide, which can lead to a dangerous condition called respiratory acidosis. And that makes total liquid ventilation very impractical, because you need a lot of complicated pumps and other equipment to make it work.

A liquid ventilator that can do this has never gotten past the prototype stage. But partial liquid ventilation, where about 40% of the lung capacity is filled with PFCs and the rest is filled with air using a normal ventilator, has shown promise in treating people with lung injuries as well as babies born prematurely. And it may not be too long before the method gets regulatory approval.

So who knows—that sci-fi future with people breathing liquid to explore far off planets might be closer than you’d think. Thanks to Patreon patron Lučka for asking, and to all of our patrons that voted for this question in our poll. If you want to pose questions like this that for us to answer, plus get tons of other cool rewards, you can head on over to patreon.com/SciShow. [♩OUTRO ].