This single centre study enrolled 197 patients with COPD requiring admission to hospital for an unexplained acute exacerbation. Patients with any evidence of lower respiratory tract infection, pneumothorax, and those requiring invasive ventilation were excluded. Patients with clinical and radiological findings deemed out of keeping with the degree of hypoxaemia were included. All patients were investigated with computed tomogram pulmonary angiography (CTPA) and venous lower limb ultrasonography.

Evidence of pulmonary embolus (PE) was found in 49 of the 197 patients (25%, 95% CI 19 to 32). This is consistent with previously published data. The diagnosis of PE was determined by positive CTPA and deep vein thrombosis (DVT) on ultrasound in 19 patients; 24 patients had a positive CTPA alone and six with a negative CTPA had DVT seen on ultrasound. The patients were retrospectively categorised into low, intermediate, and high probability according to the Geneva score. Eleven of the 119 patients (9%) in the low probability group had PE, 35 of 75 patients (46%) in the intermediate probability category had PE, and all three in the high probability group had PE.

The diagnosis of PE could not therefore be excluded on the basis of a low probability Geneva score. The only reliable risk factors identified in this study group were previous thromboembolism, malignancy, and a decreased arterial carbon dioxide tension compared with baseline.