Trauma Conditions that cause<unk>  may result from both blunt and penetrating trauma;<unk>  is often the result of a stabbing or gunshot wound.<unk>  is often found in car accident victims because of the force of the crash. Chest trauma, a major cause of<unk> , can cause air to enter the skin of the chest wall from the neck or lung. When the pleural membranes are punctured, as occurs in penetrating trauma of the chest, air may travel from the lung to the muscles and<unk>  tissue of the chest wall. When the alveoli of the lung are ruptured, as occurs in pulmonary laceration, air may travel beneath the visceral pleura (the membrane lining the lung), to the hilum of the lung, up to the trachea, to the neck and then to the chest wall. The condition may also occur when a fractured rib punctures a lung; in fact, 27% of patients who have rib fractures also have<unk> . Rib fractures may tear the parietal pleura, the membrane lining the inside of chest wall, allowing air to escape into the<unk>  tissues.<unk>  is frequently found in pneumothorax (air outside of the lung in the chest cavity) and may also result from air in the mediastinum, pneumopericardium (air in the pericardial cavity around the heart). A tension pneumothorax, in which air builds up in the pleural cavity and exerts pressure on the organs within the chest, makes it more likely that air will enter the<unk>  tissues through pleura torn by a broken rib. When<unk>  results from pneumothorax, air may enter tissues including those of the face, neck, chest, armpits, or abdomen. Pneumomediastinum can result from a number of events. For example, foreign body aspiration, in which someone inhales an object, can cause pneumomediastinum (and lead to<unk>  by puncturing the airways or by increasing the pressure in the affected lung(s) enough to cause them to burst.<unk>  of the chest wall is commonly among the first indications that barotrauma, damage caused by excessive pressure, has occurred; it suggests that the lung was subjected to significant barotrauma. Thus the phenomenon may occur in diving injuries. Trauma to parts of the respiratory system other than the lungs, such as rupture of a bronchial tube, may also cause<unk> . Air may travel upward to the neck from a pneumomediastinum that results from a bronchial rupture, or downward from a torn trachea or larynx into the soft tissues of the chest. It may also occur with fractures of the facial bones, neoplasms, during asthma attacks, when the Heimlich maneuver is used, and during childbirth. Injury with pneumatic tools, those that are driven by air, is also known to cause<unk> , even in extremities (the arms and legs). It can also occur as a result of rupture of the esophagus; when it does, it is usually as a late sign. Medical treatment<unk>  is a common result of certain types of surgery; for example it is not unusual in chest surgery. It may also occur from surgery around the esophagus, and is particularly likely in prolonged surgery. Other potential causes are positive pressure ventilation for any reason and by any technique, in which its occurrence is frequently unexpected. It may also occur as a result of oral surgery, laparoscopy, and cricothyrotomy. In a pneumonectomy, in which an entire lung is removed, the remaining bronchial stump may leak air, a rare but very serious condition that leads to progressive<unk> . Air can leak out of the pleural space through an incision made for a thoracotomy to cause<unk> . On infrequent occasions, the condition can result from dental surgery, usually due to use of high-speed tools that are air driven. These cases result in usually painless swelling of the face and neck, with an immediate onset, the crepitus (crunching sound) typical of<unk> , and often with<unk>  air visible on X-ray. One of the main causes of<unk> , along with pneumothorax, is an improperly functioning chest tube. Thus<unk>  is often a sign that something is wrong with a chest tube; it may be clogged, clamped, or out of place. The tube may need to be replaced, or, when large amounts of air are leaking, a new tube may be added. Since mechanical ventilation can worsen a pneumothorax, it can force air into the tissues; when<unk>  occurs in a ventilated patient, it is an indication that the ventilation may have caused a pneumothorax. It is not unusual for<unk>  to result from positive pressure ventilation. Another possible cause is a ruptured trachea. The trachea may be injured by tracheostomy or tracheal intubation; in cases of tracheal injury, large amounts of air can enter the<unk>  space. An endotracheal tube can puncture the trachea or bronchi and cause<unk> . Infection Air can be trapped under the skin in necrotizing infections such as gangrene, occurring as a late sign in gas gangrene, of which it is the hallmark sign.<unk>  is also considered a hallmark of fournier gangrene. Symptoms of<unk>  can result when infectious organisms produce gas by fermentation. When<unk>  occurs due to infection, signs that the infection is systemic, i.e. that it has spread beyond the initial location, are also present.
Subcutaneous emphysema
Bronchophony
Tracheal deviation
Tracheobronchomegaly
Barrel chest
Visakhapatnam gas leak
Pleural friction rub
Grand Rounds