A post-lung surgery client is placed on a chest tube drainage system.

(A) There is a separate collection bottle for drainage as part of a chest drainage system. (B) In a three-bottle chest drainage system, one bottle serves only as a pressure regulator. (C) Mediastinal chest tubes prevent accumulation of blood around the heart immediately following heart surgery. (D) The purpose of the water-seal bottle in any chest drainage setup is to allow air out of the chest, but not back in. This negative pressure promotes lung expansion.