A patient has a chest tube inserted to treat a pneumothorax. Which observation causes the nurse to conclude that the water-seal chamber of the chest drainage unit (CDU) is functioning properly?
a) Continuous bubbling in the water-seal chamber.
b) Sudden rise and fall of water in the suction control chamber.
c) Absence of fluctuation in the water-seal chamber during inspiration and expiration.
d) Persistent bubbling in the suction control chamber.
