Chapter 71

Pneumothorax occurs when air enters the potential space between the visceral and parietal pleura as a consequence of blunt trauma, penetrating trauma, or spontaneous occurrence. Iatrogenic pneumothorax occurs secondary to a diagnostic or therapeutic procedure and is a type of penetrating traumatic pneumothorax. Primary spontaneous pneumothorax (PSP) occurs in individuals without known lung disease. Secondary spontaneous pneumothorax (SSP) occurs in patients with underlying lung disease, especially chronic obstructive pulmonary disease (COPD), and generally requires more conservative treatment.

### Epidemiology

PSP has an incidence that varies with geography. In the U.S., PSP has an age-adjusted incidence of 7.4 to 18 cases per 100,000 population for men and 1.2 to 6 cases per 100,000 for women.1 For unknown reasons, the incidence in the United Kingdom is greater, estimated to be 18 to 28 per 100,000 population per year for men and 1.2 to 6 per 100,000 for women.2 PSP is primarily a disease of male smokers who have greater height-to-weight ratios. Male sex carries a 6:1 relative risk as compared with the risk for females, although more recent studies show a trend to increased cases among women, perhaps because of smoking trends.3 Smoking is an important risk factor, with a 12% lifetime risk of spontaneous pneumothorax (SP) in smoking men compared with 0.1% in nonsmokers.4 Unfortunately, 80% of smokers continue to smoke after first PSP.5 A genetic component is evidenced by clustering of cases within families such as in the autosomal-dominant Birt-Hogg-Dube syndrome with skin tumors, renal cancer, and PSP.6 Contrary to common belief, physical activity plays no role is SP. SP may rarely be associated with menses (catamenial) in women with endometriosis who have endometrial implants on the diaphragm or in the thoracic cavity. Mortality is rare in PSP (<0.1%) because most patients are younger.1,2

The incidence of SSP is comparable to PSP, with 26 (United Kingdom) and 6.3 (U.S.) per 100,000 population for men per year. Mortality is much greater in SSP due to underlying, precipitating lung disease and decreased physiologic reserve.1,2 COPD constitutes the most common cause of SSP.7 Other causes include status asthmaticus, tuberculosis, acquired immunodeficiency syndrome–related or other necrotizing pulmonary infections, cystic fibrosis, interstitial lung disease, neoplasms, and drug use.1,2,8 Pneumothorax occurs in 5% of acquired immunodeficiency syndrome patients, is associated with subpleural necrosis from Pneumocystis infection, and carries a high mortality.9 Because of necrosis of lung tissue and continued air leak, simple aspiration and nondrainage techniques fail in this group of patients.

The incidence of SP peaks in three age groups: neonates (because of hyaline membrane disease or aspiration), 20- to 40-year-olds (mostly primary pneumothorax), and older than age 40 years (mostly secondary pneumothorax). Recurrence rates are approximately 32% for primary pneumothorax and about 43% for secondary pneumothorax if no recurrence prevention procedure is performed.3,7

Hemopneumothorax occurs in 2% to 7% of patients with SP and is characterized by a large ...

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