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...
Initiating gastric decompression. Intermittent suction provides alternating periods of gastric-tube suction force followed by a release of suction, which reduces the risk of mucosal erosion. In contrast, continuous suction is the application of suction force without interruption. Intermittent suction is used for most tubes due to the risk of mucosal damage. The exception is the gastric sump tube.