No arguments there - but a short term emergency like these fat bubbles were intended for just gave the medical staff enough time (tens of minutes) to find a more permanent solution. The COVID patient is someone who may need days or weeks of oxygenation and either dies or goes home. In that case, a perfluorocarbon enema seems a more reasonable route, especially since the COVID patient is usually sedated anyways. A heart-lung machine is a pretty expensive and invasive process where your entire blood volume has to go through the machine several times a minute. If I recall, the risks of strokes and heart attacks also goes up when you are on one of those machines - blood is a finicky material that you have to treat gently or it clots instantly - it doesn't like machines. ;)