OBJECTIVE. TO study risk factors for the development of air travel-related acute venous thromboembolism. METHODS. A retrospective study of 254 patients admitted from 1988 to 1993 under the diagnosis of deep vein thrombosis (DVT) and/or pulmonary embolism (PE) identified 44 patients who developed symptoms during or after air flight. RESULTS. There were 24 males and 20 females with a mean age of 63 years. Flight times were 5-17 hours. Twenty-eight patients (63.6%) had DVT only, five patients (11.4%) PE only, and II patients (25%) DVT and PE. Ninety-five percent had extension of the thrombus above the calf popliteal vein, 10 patients; superficial femoral vein, 13 patients; common femoral vein, six patients; and iliac vein, eight patients. Five patient-related risk factors were identified: history of previous DVT (34%), presence of chronic disease or malignancy (25%), hormone therapy (16%), recent lower limb injury (11%), and recent surgery or femoral catheterization (9%). CONCLUSIONS. We can speculate about the role of seven cabin-related risk factors: low humidity, hypoxia, diuretic effect of alcohol, insufficient fluid intake, smoking, ''coach'' position, and immobilization. In travelers with patient-related risk factors, the cabin-related risk factors are superimposed and may increase the risks for air travel-related acute venous thromboembolism. Active prophylaxis is recommended.
