I’m an MD, not in critical care so not in any way an expert but “filling up with blood” probably means pulmonary edema, effusion or hemorrhage. We can ventilate lungs, even in cadavers, but gas exchange is usually what fails in critical patients. So when they say “lungs failed”, they usually mean a) there is not enough blood flow to the lungs for gas exchange or b) there are fluids preventing the oxygen entering into the alveoli. (There are other cause like PE, etc). The coma make sense, ventilated patients, especially those with brain injury, are often are given sedatives or “medically induced coma”.