Pneumomediastinum infrequently complicates diagnostic bronchoscopy. Increased airway or alveolar pressure results in air leaks to the mediastinum through existing or induced defects. Excessive cough, recurrent episodes of increased abdominal pressure, vomiting, or sneezing can all induce spontaneous pneumomediastinum. Less commonly it has been documented with lung or neck infections, esophageal or tracheal tears, and rapid increases in altitude such as during plane flights or scuba diving, with mechanical ventilation, substance abuse, and after bronchoscopy. Pneumomediastinum may be, but is not always, associated with pneumothorax.