"Acute bronchial obstruction for any reason, such as lung cancer, mucus plugs, foreign bodies, or malpositioned endotracheal tubes, can cause acute lobar collapse and a marked increase in negative intrapleural pressure around the collapsed lobe which results in gas - that is, nitrogen from surrounding tissues and blood vessels - being drawn into the pleural space around the collapsed lobe while the seal between the visceral and parietal pleura around aerated lobes remains intact."