Hamman's sign is most characteristic of

(D) Pneumomediastinum # Subcutaneous emphysema is a frequently found in pneumothorax (air outside of the lung in the chest cavity) and may also result from air in the mediastinum, pneumo- pericardium (air in the pericardial cavity around the heart). Pneumothorax (plural pneumothoraces) is a collection of air or gas in the pleural cavity of the chest between the lung and the chest wall. It may occur spontaneously in people without chronic lung conditions ("primary") as well as in those with lung disease ("secondary"), and many pneumothoraces occur after physical trauma to the chest, blast injury, or as a complication of medical treatment. Pneumopericardium is a medical condition where air enters the pericardial cavity.lt can be congenital, or introducec by a wound Hamman's crunch is caused by pneumomediastinum , and is associated with tracheobronchial injury due to trauma, medical procedures (e.g., bronchoscopy) or proximal pulmonary bleb rupture