What Causes Accumulation Of Blood In Pleurex Lung Catheter?

My dad has non small cell lung cancer DX last June he had 5 high power radiation treatments in Oct. He has had 2 bronchoscopy that were normal. His PET CT was normal and shows the lung mass is smaller. He has had his lung drained several times at the hospital all showing no cancer cells but the cells are abnormal. The Dr decided to put a plurex lung catheter in his lung and we have drained it 2 times this week once on Tuesday and the amount of fluid was 1000 or 1 liter and it was bloody fluid the Dr said he was not concerned. We drained it again today Saturday and took off 800 and it was bloody again poss. worse then on Tue. I assumed it would have some blood from putting in the catheter but I thought it would be better the second time we drained it and it was worse. Any idea what is going on.