pneumonectomy-and what to expect afterwards?!

My father is 63 and on May 25th had a full pneumonectomy. We were told about some possible side effects that they would be watching out for. Pneumonia and any infections. Well he did real well when he was in and was discharged six days later. About a week later he was back in the er, because he was really sick, vomiting involuntarily. It turned out the the internal stitches on the stump, had come loose and fluid was siphoning thru it and into the right lung. Giving him an infection where the left lung was and pneumonia in the right lung. He was in the hospital for 13 days that time. Two weeks later I had him admitted because he was really winded but his O2 level was good so we had find out why he was not feeling well and looking very pale. We found out that he had fluid around the lining of his heart, and they had to extract it, 500cc's to be exact. After that was done, he was starting to feel better. He went in the next week for an appointment with his new cardiologist(he never needed one before til after the surgery),they did an echocardiogram, and everything seemed ok. Well that week after the appt, his appetite decreased greatly and by Saturday evening, he had a fever(100.4). He took two acetametaphen and it would go down to 99. It continued through the next day, Sunday. Fever and hardly eating anything and he just did not feel well at all. He had weighed himself and he had lost 14lbs in less than 7 days. I conferred with my boyfriend, who is a trained paramedic and he said to get him to the hospital. So off I dragged him off to the er. First thing that came up funny was that his O2 level was 89. The nurse asked what it usually is for him, and I advised it is usually about 93/94. So the first thing they did was put him on oxygen. And after a few x-rays, it looked like he had pneumonia....again! So he is back in the hospital and was started on 2 different antibiotics and then moved to 4 different ones and now is back down to 2. Now I should add that my dad was diagnosed in December with lung cancer, non small cell. He did go through 8 weeks of chemo and radiation. I am just wondering if anyone else has seen this course of events. I am beginning to wonder if he is going to get chronic pneumonia.