Pediatric Pneumothorax

Pneumothorax refers to the accumulation of air or gas in the pleural space that enters through disruption of any surface of the pleura.

Classification is as follows:

• Spontaneous pneumothorax: This occurs without known disease or a precipitating factor. It can be further categorized as primary (idiopathic) pneumothorax or secondary pneumothorax.
• Secondary pneumothorax: This occurs as a complication of a chronic or acute lung disease. It is usually associated with higher morbidity and mortality than primary spontaneous pneumothorax. ^[1]
• Traumatic pneumothorax: This is caused by blunt or penetrating trauma to the chest.
• Iatrogenic pneumothorax: This is a complication of certain diagnostic or therapeutic procedures such as central line placement.

Pneumothoraces can also be classified as either simple or complicated, depending on size, symptoms, progression, and recurrence. The size of a pneumothorax is not as important as the degree of clinical compromise. ^[1]

See the images below.

Pneumothorax; left side.

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Spontaneous pneumothorax occurs via rupture of the visceral pleura, whereas traumatic pneumothorax may occur following injury to either pleural layer. In both types, a loss of intrapleural negative pressure causes lung collapse. The main physiologic consequences of a pneumothorax are a decrease in vital capacity and a decrease in partial pressure of oxygen (PaO₂). Most patients with a pneumothorax have a reduced PaO₂ and an increased alveolar-arterial gradient. The reduction in PaO₂ appears to be caused by areas with low ventilation-perfusion ratios, anatomic shunts, and alveolar hypoventilation. ^[2]

Simple pneumothorax occurs when air in the pleural space does not build up significant pressure but allows the lung to collapse without further expansion of the pneumothorax. Usually, small pneumothoraces are asymptomatic and well tolerated.

Complicated pneumothorax consists of continued air leakage into the pleural space that cannot exit during exhalation, resulting in progressive lung collapse. The positive pressure within the hemithorax causes a collapse of the involved lung and a shift of the mediastinal structures to the contralateral side, creating a tension pneumothorax, a life-threatening emergency. This causes a decrease in cardiac output as a consequence of decreased venous return that could lead to rapidly progressive shock and cardiorespiratory arrest if not recognized and treated. Secondary pneumothorax can be a potential life-threatening event in patients with lung disease because they may already have decreased cardiopulmonary reserve.

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Tension pneumothorax in an infant.

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The most common risk factors for pneumothorax are smoking, male gender, family history of spontaneous pneumothorax, tall lean body habitus, premature delivery, and obstructive pulmonary disease. Pneumothorax can be associated with Valsalva maneuver, but it is usually not associated with physical exertion as it is as likely to occur during sedentary activity. ^{[1, 3]} Air leak usually occurs from rupture of apical blebs, as opposite to distention along the intrapulmonary vascular bundle, with subsequent air leakage into the pleural space. Inhalation of some toxic substances (eg, crack cocaine) can also lead to this condition.

Spontaneous secondary pneumothoraces may occur in patients with underlying lung diseases or any disease that promotes air leakage, such as asthma or cystic fibrosis. ^[4] These patients also have a high risk of recurrence, especially if pleural blebs or bullae are the cause of the pneumothorax. ^[3] The presence of an apical cyst or bullae in other patients is not necessarily predictive of recurrence. ^{[5, 6]}

Other conditions associated with the development and recurrence of spontaneous pneumothorax include parenchymal diseases (eg, interstitial lung disease, emphysema), infections (eg, necrotizing pneumonia, tuberculosis, pneumonia in immunocompromised hosts), malignancy (eg, lymphoma, metastasis), and connective-tissue disorders (eg, Marfan syndrome, Ehlers-Danlos syndrome, juvenile idiopathic arthritis, systemic lupus erythematosus, polymyositis, dermatomyositis, sarcoidosis, Langerhans cell histiocytosis, alpha-1 antitrypsin deficiency, Birt-Hogg-Dubé syndrome). ^[3] Spontaneous pneumothorax is also common in patients with lymphangioleiomyomatosis.

When trauma results in pneumothorax, it may be secondary to blunt or penetrating trauma. Penetrating trauma results in an open or communicating pneumothorax.

Iatrogenic causes of pneumothorax include central line placement, thoracentesis, cardiothoracic surgery or biopsy, mechanical ventilation, and cardiopulmonary resuscitation.

Although all age groups are affected, the peak incidence of pneumothorax occurs in individuals aged 16-64 years. ^[7] In the pediatric population, the overall incidence of pneumothorax is 5-10 cases per 100,000 children younger than 18 years. The rate of pneumothorax is relatively higher during the newborn period. ^[8] Primary spontaneous pneumothorax may have a higher recurrence rate in children than in adults. There is a strong (6:1) male predominance for spontaneous pneumothorax. It can also present in reproductive-age girls as catamenial pneumothorax. ^{[1, 5]}

The prognosis is often favorable, especially if it was an isolated event and treatment was initiated early. Prognosis also varies depending in patient’s underlying disease and pulmonary reserve. If other trauma was sustained at the same time or tension pneumothorax occurred with subsequent shock and hypoperfusion, the prognosis worsens. If the patient was allowed to be hypoxic for a long period, brain injury is possible.

Recurrence after the first episode of primary spontaneous pneumothorax in children is frequent and difficult to predict. ^[9] The recurrence rate of spontaneous pneumothoraces can range from 40-87%. The risk of recurrence is increased if the initial episode was slow to resolve and if there is ongoing cigarette smoking following the development of spontaneous pneumothorax. A high incidence of recurrence is noted after the first episode of a secondary pneumothorax and in patients who participate in activities such as deep sea diving. Patients with obstructive pulmonary disease (eg, asthma, cystic fibrosis) have an especially high rate of recurrence. ^{[3, 4]}

For patient education information, see the Lung Disease and Respiratory Health Center and the patient education article Collapsed Lung (Pneumothorax).