[7] Although the underlying conditions require treatment, subcutaneous emphysema usually does not; small amounts of air are reabsorbed by the body.

[5] A significant case of subcutaneous emphysema can be detected by touching the overlying skin, which will feel like tissue paper or Rice Krispies.

[11] Rib fractures may tear the parietal pleura, the membrane lining the inside of chest wall, allowing air to escape into the subcutaneous tissues.

[13] When subcutaneous emphysema results from pneumothorax, air may enter tissues including those of the face, neck, chest, armpits, or abdomen.

[5][20] Trauma to parts of the respiratory system other than the lungs, such as rupture of a bronchial tube, may also cause subcutaneous emphysema.

[13] 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.

[13] It may also occur with fractures of the facial bones, neoplasms, during asthma attacks, as an adverse effect of the Heimlich maneuver, and during childbirth.

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 subcutaneous emphysema.

[8] On infrequent occasions, the condition can result from dental surgery, usually due to use of high-speed tools that are air driven.

[9][21] Air is able to travel to the soft tissues of the neck from the mediastinum and the retroperitoneum (the space behind the abdominal cavity) because these areas are connected by fascial planes.

[4] From the punctured lungs or airways, the air travels up the perivascular sheaths and into the mediastinum, from which it can enter the subcutaneous tissues.

[17] Spontaneous subcutaneous emphysema is thought to result from increased pressures in the lung that cause alveoli to rupture.

[5] In spontaneous subcutaneous emphysema, air travels from the ruptured alveoli into the interstitium and along the blood vessels of the lung, into the mediastinum and from there into the tissues of the neck or head.

On a chest radiograph, subcutaneous emphysema may be seen as radiolucent striations in the pattern expected from the pectoralis major muscle group.

CT scanning is so sensitive that it commonly makes it possible to find the exact spot from which air is entering the soft tissues.

The presence of subcutaneous emphysema in a person who appears quite ill and febrile after bouts of vomiting followed by left chest pain is very suggestive of the diagnosis of Boerhaave's syndrome, which is a life-threatening emergency caused by rupture of the distal esophagus.

[4] Of note, there are no changes in the pulse oximetry or airway pressure in subcutaneous emphysema, unlike in endobronchial intubation, capnothorax, pneumothorax, or CO2 embolism.

[1] Most of the time, SCE itself does not need treatment (though the conditions from which it results may); however, if the amount of air is large, it can interfere with breathing and be uncomfortable.

When the amount of air pushed out of the airways or lung becomes massive, usually due to positive pressure ventilation, the eyelids may swell so much that the patient cannot see.

The pressure of the air may impede the blood flow to the areolae of the breast and skin of the scrotum or labia which can lead to necrosis.

[32] Since treatment usually involves dealing with the underlying condition, cases of spontaneous subcutaneous emphysema may require nothing more than bed rest, medication to control pain, and perhaps supplemental oxygen.

A case was reported at the University Hospital of Wales of a young man who had been coughing violently causing a rupture in the esophagus resulting in SE.

[5] The cause of spontaneous subcutaneous emphysema was clarified between 1939 and 1944 by Macklin, contributing to the current understanding of the pathophysiology of the condition.