nscc 3b lung cancer - painful stomach bloating, gas side effect; heimlich valve

Today my husband is laying on the couch in alot of pain, caused from this stomach bloating issue. He just got out of the hospital a week ago, he was there for 3 weeks. He has a collapsed lung, with alot of fluid that they drained, but were not able to open back the lung. The fluid is starting to come back into the lung and we see the doctor tomorrow to discuss the next step. It may be a heimlich valve. Over the last 3-4 months, several times he has had this very painful bloating, he says it's like the food isn't digesting. He's been on different laxatives and has not had a recent constipation problem. Has anyone out there had to deal with this issue if if so, what's worked? or what hasn't worked?