Question about Pleurex Catheter

Here's a question for anyone who's had a pleurex catheter. Mom has been doing well with hers since her surger about 3 weeks ago. She started chemo last week and today she's had some pain during the removal of fluid. She said it feels like a pulling sensation (which makes sense due to the suction), but today it was actually sort of painful.

They've been taking about 500ml from her every day. The cannister holds about 550 or 600ml, so I tend to think they were just filling the cannister and then stopping. I want to believe that the increase in sensation she's having may be due to the fact that there is less fluid in there to drain, so when they get close to 500ml, it starts to pull too much on her lung. Does that make any sense? Or am I being too optomistic?

I'd be grateful for any thoughts or experiences you can share. We're seeing the surgeon tomorrow, which is good, but he's a bit of an ass, so I'm not sure he'll really listen to what's going on before making some loud prcolimation. ;-)

Thanks,
Cris.