Clinical meaning
Pulmonary embolism results from thromboembolic occlusion of pulmonary arteries, most commonly from lower extremity or pelvic DVT (>90% of cases). The embolus obstructs blood flow to distal pulmonary vasculature, creating dead-space ventilation (ventilated but not perfused). This causes ventilation-perfusion (V/Q) mismatch, intrapulmonary shunting, and hypoxemia. Massive PE (>50% of pulmonary vasculature occluded) causes acute right ventricular failure due to sudden increase in pulmonary vascular resistance, leading to obstructive shock. Virchow's triad — venous stasis, endothelial injury, and hypercoagulability — underlies most thromboembolic events. The nurse must perform rapid respiratory and hemodynamic assessment, initiate anticoagulation therapy, monitor for deterioration, and coordinate advanced interventions.
Exam relevance
Risk factors: - Deep vein thrombosis (most common source) - Recent surgery (orthopedic, abdominal, pelvic) - Prolonged immobility (>72 hours bed rest, long flights) - Active malignancy - Pregnancy and postpartum (hypercoagulable state) - Oral contraceptives or hormone replacement therapy - Obesity - Prior history of VTE - Central venous catheter placement