Having major problems in using the vac with a patient that has an fistual wound in her small intestine.The output is alot. Keep having to change the dressing b/c can not seem to figure out the best way to use the vac as after an hour or so begins to leak? Any tips or special things that can be used...Also patient is in alot of pain from constant changing of the dressing as the wound is only a week and half old.