It is an air gap that allows air to escape rather than building up in the pipe and creating an air hammer within the pipes (banging noise), and problems with drainage. (think about pouring out of a can that doesnt have the second hole punched in it.
Suction Therapy : Suction therapy is provided to assist in the removal of bronchial secretions that cannot be expectorated by the patient spontaneously. Suct...
removal of material from the wall of a cavity or other surface by scraping with a curette. 1  suction curettage (vacuum curettage) a method of induced abortion, consisting of removal of the uterine contents, after dilatation, by means of a hollow curette introduced into the uterus, through which suction is applied.