Transplanted lungs are vulnerable, so if you get sick a few times as Will did (first with post-transplant lymphoproliferative disorder (a kind of cancer) then with chronic rejection, then pneumonia, then Hodgkin's lymphoma, then pneumonia again) you end up with lung damage. Among other things, the lung damage means that the lungs get infected more easily and the infections are more difficult to fully get rid of.
"Airway clearance" as far as I understand it means loosening up the gunk in ones lungs and aggressively coughing it up to get rid of it. Will doesn't like adding daily airway clearance to his routine. It takes time -- about 90 minutes or so each day -- and it makes his chest hurt. Mostly, though, I think the hard part is that it was one of the CF related obligations he had hoped to leave behind forever after transplant. But he does do it, most days, because it makes him feel better and hopefully will make hospitalizations and use of IV antibiotics less frequent. Will recently started using nebulized hyper tonic saline (a 3% solution) to help with airway clearance and it does seem to help him. It seems like inhaling the saline mist makes the gunk in his lungs more susceptible to moving around and being coughed up.
For those who haven't seen it before, the maintenance gear is, from left to right: basket of nebulizer mouth-pieces ready to be taken apart and sterilized; the compressor, which blasts air into the saline to turn it into a mist (propped up for photo purposes on an albuterol inhaler which you can barely see); box of colistimine ready to be mixed up, sometimes Will takes antibiotics by inhalation; two little ampules of the saline solution, ready to go; and the home PFT tester used to measure whether lung function is staying the same, getting better, or getting worse. (More on that some other time.)
We're grateful beyond words that these treatments exist, and that Will persists in them with (mostly!) good humor and grace.