One, two, three.

Skinny face, yeah.

All right, a lot of you guys probably heard about this thing called pruning for coronavirus

patients, putting patients on their belly to improve their oxygenation, their blood oxygen

levels.

How does this work?

Well, this doctor is going to try to explain it to you, and I haven't thought about this

much since medical school.

So here goes.

It turns out that most of human lung tissue is in the back.

Why is that?

You would think it'd be all over, right?

Well, we have this thing called the heart, sits right about here.

And there's other structures in the center of your chest, and then your belly, your abdominal

contents push up on the diaphragm.

And so all that is to say, a lot of our lung tissue is towards our backs.

So this is what happens in patients who get sick with, say, coronavirus or other things

that cause acute respiratory distress syndrome.

The alveoli, the little sacks that air goes into in the lungs.

Those alveoli are surrounded by blood vessels that exchange gas.

So they're coming into the lung from the right side of the heart, and oxygen is coming into

that blood vessel through the little air sac, the alveolis, and carbon dioxide is going

...