Mediastinal shift

Mediastinal shift a shifting or moving of the tissues and organs that comprise the mediastinum (heart, great vessels, trachea, and esophagus) to one side of the chest cavity … This can produce compression of the other lung and kinking or twisting of one or more of the great blood vessels, which in turn seriously impairs blood flow to and from the heart.

(medical-dictionary.thefreedictionary.com)