Observer variability in volumetric blood flow measurements in leg arteries using duplex ultrasound

Duplex ultrasound volumetric flow measurements have not found a major clinical use because of variability caused by errors in estimating cross-sectional area (CSA) and in measuring time averaged mean velocity (TAMeV). We determined inter- and intraobserver variation in volumetric blood flow measured at rest in the common femoral artery (CFA) and its main branches, the superficial femoral (SFA) and profunda femoris (PFA) arteries, in 20 normal subjects. The product of TAMeV and CSA was taken as volumetric flow. The coefficient of variation of TAMeV was consistently greater than that of CSA. Interobserver variation for blood flow (16.2%, 20.2% and 40.3% for CFA, SFA and PFA, respectively) was larger than intraobserver variation (13.0%, 15.1%, 21.2%). In conclusion, these data define the minimum changes in VQ that can be realistically detected and indicate that, with modern duplex Doppler equipment, volumetric flow can be used as a reliable haemodynamic measure for monitoring patients before and after surgical or radiological intervention.