Yeah. A lot of guesswork. Fascinating how so many intensivists talk about this as something they’ve never seen before. Really compliant lungs and people dropping their sats to their boots without realising it. I’ve also never heard proning talked up this much.
To be honest, it's not that shocking from a physiological point of view. Shortness of breath and distress mainly hinges on accumulation of CO2 and a high work of breathing. We don't see these patients with abnormal PCO2 levels. They can get rid of that, albeit with a high required effort. Hypoxia usually causes respiratory distress if you're already accustomed to elevated PCO2 levels. I mean, you already know this so I'm not looking to educate you, just saying that it makes sense in a way.
Proning is a cornerstone in classic ARDS treatment, just that it's rare enough to have patients with such severe cases of ARDS since there's an underlying disorder that is treatable. Usually, the ARDS clears before you've exhausted all supine treatment options. In my ICU, I'd say that we have (ballpark figure) 15 patients in a year that require proning.
In moderate to severe ARDS, it halved the mortality from 32% to 16% in one RCT, which is quite a lot better than many other ICU treatments. The "two phenotypes of Covid-19" might be a thing or it may just be two phases of the same disorder, but in the ARDS-like state, it makes a lot of sense to prone the patients to improve ventilation/perfusion matching.
But yeah, regarding your main point, it's a weird fecking disease. I mean, we see people with the flu getting this bad but by the time you tube them the infection's already getting better so you only need to ride it out and let them recover from the effort of breathing. We've had patients in our ICU for nigh on three weeks now that look the same on their CXR as they did when they arrived.