Which factor most increases pretest probability for Pulmonary Embolism?

Prolonged immobilization after hip surgery is one of the strongest clinical risk factors for deep vein thrombosis and subsequent pulmonary embolism. Immobility promotes venous stasis, one component of Virchow's triad (stasis, hypercoagulability, endothelial injury), which describes the pathophysiological conditions predisposing to thromboembolism. Hip surgery adds additional risk factors: direct endothelial trauma from the procedure and a postoperative hypercoagulable state from surgical stress and inflammatory mediators. Taken together, prolonged immobilization after hip surgery dramatically increases pretest probability for PE on clinical scoring tools such as the Wells Criteria. Productive cough with green sputum (option A) is characteristic of a respiratory infection such as pneumonia or bronchitis, not PE. Seasonal allergies (option C) are associated with rhinitis and asthma but carry no recognized thromboembolic risk. A recent influenza vaccine (option D) has no established association with PE risk. When assessing a patient for PE, nurses and clinicians should be alert to classic risk factors — recent surgery, immobility, prior DVT/PE, malignancy, pregnancy, oral contraceptive use — and escalate evaluation accordingly using validated clinical decision tools.