"Long haul" flight and deep vein thrombosis: A model to help investigate the benefit of aspirin and below-knee compression stockings

Abstract

Objective: to develop a model simulating factors of "long haul" flight to investigate the relationship with DVT. Materials and methods: volunteers (19 males: 20 females) sat for 6 h in a warm (>25°C), dry environment, limited in movement, consuming alcohol (40% ml of 40% alcohol/hour) and salted foods (300g). Half of the subjects received 150 mg aspirin and wore especially designed below-knee, compression stockings (Class 1 profile). Changes in full blood counts were recorded, and as an indication of DVT formation, plasma was analysed for D-dimer. Limb swelling was assessed from leg measurements. Results: after 6 h, in controls, there were significant rises in platelet packing (Pct; p<0.04), total platelet numbers (p<0.003) and total numbers of white blood cells (WBC's; p<0.001). With aspirin plus stockings, there were similar significant rises in total platelet numbers (p<0.002) and total WBC's (p<0.001). In both groups, significant rises were seen in all WBC types (except basophils). Wearing compression stockings prevented calf swelling seen in controls after 6 h (p<0.002). No subject developed a DVT, or a change in levels of D-dimer. Conclusion: changes in the cellular components of blood, particularly WBC's, combined with vaso-compression and reduced flow could predispose towards DVT. Aspirin, combined with compression stockings, may provide prophylaxis.