I had my first patient with a chest tube the other day, to drain peritoneal fluid. The tube was not hooked up to suction. I noticed there was no tidalling of the float ball. I informed my colleagues and neither of them thought this signified an occlusion. They argued that it would only tidal if there was a pneumothorax. Everything I have read about chest tubes has said that a tube that does not tidal signifies an occlusion. Is this incorrect?