Given the news yesterday of this guy, Mansour Ojjeh, resigning here is what operation he had in 2013
https://www.autosport.com/f1/news/111089/ojjeh-recovering-from-lung-transplant
Fast forward to yesterday and we have this from Niki Lauda:
https://www.racefans.net/2018/08/07/lauda-making-very-satisfying-progress-after-transplant-hospital/
Ojjeh is way farther up the food chain then Niki. Ojjeh is at the Bernie Eccelstone and Max Mosely level. I now think that Michael Schumacher's "accident" in 2013 was his dropping out.
Speculation now about him coming to the US to be treated.