Frothy sputum is most characteristic of which pulmonary disorder?

A. Tuberculosis is incorrect because TB primarily produces blood-tinged sputum (hemoptysis). This occurs due to cavitation and erosion of pulmonary blood vessels caused by Mycobacterium tuberculosis infection. TB sputum is typically thick, sometimes streaked with blood, but not frothy, and is associated with chronic cough, night sweats, fever, and weight loss.

B. Pulmonary edema is correct because it involves accumulation of fluid within the alveoli, which interferes with gas exchange. The presence of fluid, particularly protein-rich fluid from increased hydrostatic pressure in cardiogenic pulmonary edema, mixes with air during breathing to produce frothy, often pink-tinged sputum. This frothy sputum is a classic and early clinical indicator of acute pulmonary edema, which may result from left-sided heart failure, myocardial infarction, fluid overload, or acute respiratory distress syndrome (ARDS). Other associated signs include dyspnea, orthopnea, crackles or rales on auscultation, tachypnea, and hypoxemia. Recognizing frothy sputum is critical because pulmonary edema can rapidly progress to respiratory failure if untreated.

C. Cystic fibrosis is incorrect because this genetic disorder leads to thick, sticky, and often purulent or yellow-green mucus due to defective chloride and water transport in epithelial cells. While cystic fibrosis patients produce large amounts of mucus that can cause airway obstruction and recurrent infections, their sputum is viscous rather than frothy. Chronic cough and recurrent respiratory infections are more characteristic of cystic fibrosis.

D. Emphysema is incorrect because emphysema primarily involves alveolar wall destruction, loss of elasticity, and hyperinflation, resulting in airflow obstruction. Sputum production is usually minimal, and when present, it is not frothy, since the disease affects the alveoli rather than causing alveolar fluid accumulation. Patients may present with dyspnea, barrel chest, and prolonged expiration rather than significant sputum production.