Pneumothorax and pneumomediastinum are examples of air leak syndromes in which air accumulates in the spaces outside the lung airways and alveoli. Pneumothorax refers to the abnormal presence of air in the pleural space, whereas pneumomediastinum describes accumulation of air in the mediastinum. Air leak can be traumatic, iatrogenic, or spontaneous. Primary air leak occurs in children without clinically apparent lung disease, and secondary pneumomediastinum and pneumothorax refer to those with known underlying pulmonary disease (e.g. asthma, cystic fibrosis). Air leak secondary to barotrauma from positive-pressure ventilation or after surgery is commonly categorized as iatrogenic.
The prevalence and incidence of air leak syndromes is better known in adults than in children. The majority of patients present in the second and third decade of life. Therefore older pediatric patients are often included within adult studies. The most recent pediatric data suggests that the overall incidence of spontaneous pneumothorax in patients less than 18 years of age is 3.41 per 100,000, with fewer than 7% occurring in children younger than 10 years of age.1 Secondary pneumothorax occurs at an annual incidence of 0.6% in cystic fibrosis patients, and pneumomediastinum in 0.3% of asthmatic patients in a children’s emergency department setting.2,3
Although patients with primary spontaneous pneumothorax (PSP) do not have underlying lung disease, computed tomography (CT) and surgical findings show that the majority have subpleural bullae, which may be ipsilateral or contralateral to the pneumothorax. The cause of such bullae is not fully understood, but they probably represent imbalances in protease and antiprotease enzymes leading to emphysema-like changes. Cigarette smoking increases the risk of the development of pneumothorax by nearly 10 times, although the magnitude of the risk from secondhand exposure in pediatric patients is not known.4 A specific gene mutation for pulmonary cysts has been identified in some familial cases.5
Increased intra-alveolar pressure, often from inflammation of small airways, results in tension on the alveolar wall and, ultimately, rupture leading to pneumothorax. Alternatively, air leak occurring within the interstitium can track through the hilum and collect in the mediastinum (causing pneumomediastinum), or rupture into the pleural space leading to pneumothorax.5
Patients with PSP typically present with an acute onset of pleuritic chest pain, usually described as sharp initially, becoming dull over time, and frequently resolving after 24 hours even without treatment. Onset frequently occurs while the patient is at rest. Many patients endorse dyspnea. Ipsilateral shoulder pain and dry cough are also common.
Physical examination findings vary depending on the size of the pneumothorax. Patients with small pneumothoraces (i.e. <15% of the hemithorax) may show only tachycardia or subjective dyspnea, or may have completely normal findings. In those with larger pleural air collections, examination findings include decreased chest wall movement and ...