Elevated carbon dioxide levels in the blood is called:

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.

A. Varicose veins is incorrect because varicose veins typically cause bilateral or localized superficial venous distention, aching, and heaviness, rather than the acute unilateral swelling, warmth, and redness seen with DVT.

B. Peripheral artery disease is incorrect because PAD usually causes pale, cool, or cyanotic extremities, weak pulses, and pain with exertion (intermittent claudication), rather than unilateral redness, warmth, and swelling.

C. Deep vein thrombosis (DVT) is correct because DVT involves formation of a blood clot in a deep vein, often in the leg. Classic signs include unilateral swelling, redness, warmth, pain, and tenderness, usually in the calf or thigh. DVT is a medical emergency because the clot can dislodge and travel to the lungs, causing a pulmonary embolism (PE). Risk factors include immobility, surgery, pregnancy, obesity, and hypercoagulable states.

D. Intermittent claudication is incorrect because claudication refers to exercise-induced muscle pain caused by arterial insufficiency, not venous clot formation. It does not typically cause unilateral swelling or redness.