Exactly what I thoughtThe cross section of a lung is a triangle with the largest side to the rear of the body.
Lying on your back (supine), the fluid (pneumonia) fills a large surface area. If you are placed 'prone' the fluid moves to the front and more space is free to exchange air. These patients are usually ventilated and heavily sedated.
https://jamanetwork.com/journals/jama/fullarticle/2769872
They're usually on a 20h prone / 4h supine schedule.
It is also encouraged for non ventilated patients with breathing difficulties.
Just kidding thanks