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Michael E. Hanley, MD

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Essentials of Diagnosis

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  • • The most common symptoms of pneumothorax are chest pain and dyspnea.
  • • Physical signs include hyperresonant percussion, diminished tactile and vocal fremitus, and decreased or absent breath sounds.
  • • Laboratory abnormalities include hypoxia and a widened P(a–a)O2 gradient. Pco2 may be either decreased or increased.
  • • Radiographic signs include the peripheral absence of lung markings and the presence of a pleural “stripe” that is strictly intrathoracic.

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General Considerations

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Pneumothorax, defined as the presence of air within the pleural space, is classified as either spontaneous or traumatic. Spontaneous pneumothorax occurs without obvious cause and is subclassified as either primary or secondary. Primary spontaneous pneumothorax occurs in the absence of underlying lung disease. Secondary spontaneous pneumothorax occurs as a complication of underlying lung disease. The incidence of primary and secondary pneumothorax is similar, with both conditions being more common in males than females. The incidence of primary spontaneous pneumothorax in a longitudinal health study in Olmsted County, Minnesota was 7.4/100,000/year in males and 1.2/100,000/year in females. It is more common in younger persons, with a peak incidence in the third decade of life, and is rare after age 40. The incidence of secondary spontaneous pneumothorax in the Olmsted County, Minnesota study was 6.3/100,000/year in males and 2.0/100,000/year in females. Secondary spontaneous pneumothorax is more commonly associated with severe respiratory compromise due to lack of significant respiratory reserve from the underlying lung disease.

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Traumatic pneumothorax, which results from direct or indirect trauma to the chest, is subclassified as either iatrogenic or noniatrogenic. Iatrogenic pneumothorax is the most common type of pneumothorax.

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Tension pneumothorax occurs when intrapleural pressure exceeds atmospheric pressure throughout expiration. Although any pneumothorax can cause this, the most common cause of tension pneumothorax is barotrauma from positive pressure mechanical ventilation. Tension pneumothorax is a medical emergency that is frequently associated with hemodynamic instability and considerable mortality.

Barton ED: Tension pneumothorax. Curr Opin Pulmon Med 1999;5:269.   [PubMed: 10407699] (Good review of the clinical manifestations and pathophysiology of tension pneumothorax.)

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Pathogenesis

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Primary spontaneous pneumothorax results from rupture of subpleural emphysematous blebs. The blebs tend to occur more commonly in lung apices. Although the etiology of the blebs is unknown, epidemiological observations that identify risk factors for primary spontaneous pneumothorax offer clues to processes that may contribute to their development. These studies indicate that tobacco use, body habitus, and family history are risk factors for this condition. For example, primary spontaneous pneumothorax is more common in tall, thin males. There is also a familial tendency to this type of pneumothorax; up to 11% of patients with primary spontaneous pneumothorax have a family history of spontaneous pneumothorax. Patients with primary spontaneous pneumothorax are also more likely to have bronchial abnormalities such as narrowed airways and missing or ...

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