A 62-year-old woman with a 10-year history of chronic obstructive pulmonary disease (COPD) and recent hospitalization for acute exacerbation (discharged 2 weeks ago) presents with progressive dyspnea over 3 days, mild hemoptysis, and pleuritic chest pain. She is on long-term oxygen therapy. Vital signs: HR 102/min, BP 128/75 mmHg, RR 24/min, SpO₂ 91% on supplemental oxygen. Chest X-ray shows a new wedge-shaped opacity in the left lower lobe. Arterial blood gas shows pH 7.38, PaCO₂ 48 mmHg, PaO₂ 65 mmHg on FiO₂ 0.40. D-dimer is 1.9 μg/mL. Which of the following clinical findings would be most helpful in increasing the pretest probability of pulmonary embolism in this patient?