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...
1 Reflexology - applied pressure to specific points on the foot, and sometimes the hand, to induce pain relief in other parts of the body or promote relaxation.  Massage therapy - the manipulation of tissue and joints to enhance their function and to promote relaxation.