Flail chest is a serious condition that can lead to long-term disability and even death. For a person to draw a breath, the muscles around the rib cage and the diaphragm have to move to expand the chest cavity.This creates a vacuum that is filled as air enters the lungs.lail chest is almost always linked to severe blunt trauma, such as a serious fall or car accident, in terms of cause. But it can develop as a result of less severe impacts.