Transplant evaluation comes with a whole slew of testing that requires multiple days of hospitalization.  

CT scans to evaluated the vasculature of the Liver which showed multiple inefficient angiogensis which is most likely putting a strain on to the liver causing the hepatopulmonary syndrome.

Although it is speculation the increase blood flow to the liver lead the heart and lungs to have to work extra hard- causing those organs to weaken dropping the oxygen saturation further.  

With this comes immense amount of fatigue from daily menial tasks.

Eileen's parents both underwent CT scans as part o the evaluation of the donor process.  Pending results.