it occasionally progresses to a state "massive subcutaneous emphysema" which is quite uncomfortable and requires surgical drainage. 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. the latter are urgent situations requiring rapid, adequate decompression. severe cases can compress the trachea and do require treatment. in severe cases of subcutaneous emphysema, catheters can be placed in the subcutaneous tissue to release the air. small cuts, or "blow holes", may be made in the skin to release the gas. when subcutaneous emphysema occurs due to pneumothorax, a chest tube is frequently used to control the latter; this eliminates the source of the air entering the subcutaneous space. if the volume of subcutaneous air is increasing, it may be that the chest tube is not removing air rapidly enough, so it may be replaced with a larger one. suction may also be applied to the tube to remove air faster. the progression of the condition can be monitored by marking the boundaries of the emphysema on the patient's skin. 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. breathing oxygen may help the body to absorb the subcutaneous air more quickly. prognosis air in subcutaneous tissue does not usually pose a lethal threat; small amounts of air are reabsorbed by the body. once the pneumothorax or pneumomediastinum that causes the subcutaneous emphysema is resolved, with or without medical intervention, the subcutaneous emphysema will usually clear. however, spontaneous subcutaneous emphysema can, in rare cases, progress to a life-threatening condition, and subcutaneous emphysema due to mechanical ventilation may induce ventilatory failure. history the first report of subcutaneous emphysema resulting from air in the mediastinum was made in 1850 in a patient who had been coughing violently. in 1900, the first recorded case of spontaneous subcutaneous emphysema was reported in a bugler for the royal marines who had had a tooth extracted: playing the instrument had forced air through the hole where the tooth had been and into the tissues of his face. since then, another case of spontaneous subcutaneous emphysema was reported in a submariner for the us navy who had had a root canal in the past; the increased pressure in the submarine forced air through it and into his face. 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. 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.