Deep-vein thrombosis in long-haul flights

Since the randomisation code was not broken there were no data available to report. [...]without the actual frequency of symptomless calf-vein thrombosis detected by duplex ultrasonography after long haul air travel, no accurate calculation can be made. Since no study of this type had been done previously we had to calculate the required sample size after doing the study, as we state. Duplex ultrasound imaging was done by experienced vascular technologists to assess the frequency of acute DVT in preflight volunteers, spontaneous DVT in the study population (none was found), and the effect of air travel.