Variability and reproducibility of arterial Doppler waveforms.

The variability and reproducibility of arterial Doppler waveforms are influenced by factors such as operator experience, physiological changes in the patient, and the type of Doppler processing system. Some aspects of these were studied using Laplace transform analysis of waveforms from the femoral and posterior tibial arteries of normal subjects and arteriopaths. Five consecutive waveforms were obtained from the femoral and posterior tibial arteries of normal subjects during about 1 hr of supine rest. Group 1 (n = 20) was studied 9 months before Group 2 (n = 11), early in the operator's experience of waveform recording. Variability (root mean square) of femoral and posterior Laplace delta decreased from 16.9 to 12.5%, and 23.3 to 17.9% respectively (P less than 0.05 in each case). In arteriopaths (n = 8) there was a trend to more variable results at femoral level (only significant in the case of Laplace omega 0 - P less than 0.05), while posterior tibial results tended to be less variable. Normal subjects examined in the longer term (n = 4), with a mean interval of 28 days between recordings, did not show significantly greater variability than those examined over 1 hr. There was no significant difference in variability of results in normal subjects (n = 30) using instantaneous average Doppler processing compared with maximum frequency processing, except in the case of posterior tibial Laplace omega 0 (maximum frequency more variable - P less than 0.05).