Pneumothorax, which is the accumulation of air in the pleural space, may result from external trauma or from leakage of air from the lungs or airways. Spontaneous primary pneumothorax (no underlying cause) occurs in teenagers and young adults, more commonly in tall, thin males and smokers. Factors predisposing to secondary pneumothorax (underlying cause identified) include barotrauma from mechanical ventilation, asthma, cystic fibrosis, trauma to the chest, and severe necrotizing pneumonia.
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The most common signs and symptoms of pneumothorax are chest and shoulder pain and dyspnea. If the pneumothorax is large and compresses functional lung (tension pneumothorax), severe respiratory distress and cyanosis may be present. Subcutaneous emphysema may result when the air leak communicates with the mediastinum. Physical findings associated with pneumothorax include decreased breath sounds on the affected side, a tympanitic percussion note, and evidence of mediastinal shift (deviation of the point of maximal impact [PMI] and trachea away from the side of the pneumothorax). If the pneumothorax is small, there may be few or no clinical findings. However, the patient’s clinical condition can deteriorate rapidly if the pneumothorax expands, especially if the air in the pleural space is under pressure (tension pneumothorax). This is a life-threatening condition that can result in death if the pleural space is not decompressed by evacuation of the pleural air.
The presence of a pneumothorax can usually be confirmed by upright chest radiographs. Computed tomography (CT) scans of the chest are useful in quantifying the size of pneumothoraces and differentiating air within the lung parenchyma (cystic lung disease) from air in the pleural space and for identifying subpleural blebs that may be present in spontaneous recurrent pneumothoraces. In infants, transillumination of the chest wall may be of some use in making a rapid diagnosis of pneumothorax.
The type of intervention depends on the size of the pneumothorax and the nature of the underlying disease. Small pneumothoraces (<20% of thorax occupied with pleural air) may notrequire intervention as they often resolve spontaneously. Inhaling high concentrations of supplemental O2 may enhance reabsorption of pleural air by washing out nitrogen from the blood.Larger pneumothoraces and any tension pneumothorax requireimmediate drainage of the air, preferably via chest tube. In anemergency situation, a simple needle aspiration may suffice,although placement of a chest tube is often required for resolution. In patients with recurrent or persistent pneumothoraces,sclerosing the pleural surfaces to obliterate the pleural space(pleurodesis) may be necessary. This can be done either chemically, by instilling talc or sclerosis agents (doxycycline) throughthe chest tube, or mechanically, by surgical abradement. Surgical approaches, open thoracotomy and video-assisted thoracoscopic surgery (VATS), enable visualization of the pleural spaceand resection of pleural blebs, when indicated.
Pneumomediastinum results from the dissection of air from the pulmonary parenchyma into the mediastinum. It is usually a mild, self-limited process that does not require aggressive intervention. The most common causes in children are severe forceful coughing and acute asthma exacerbations. Common symptoms are chest pain and dyspnea. There are often no physical findings, although a crunching noise over the sternum can sometimes be appreciated on auscultation, and subcutaneous emphysema may be detected about the neck. The diagnosis is confirmed by chest radiograph, and treatment is directed toward the underlying lung disease.