The quantitation of arterial elasticity from Doppler flow measurements.

The pattern of phasic pressure and flow in an artery is related to the components of the impedance of that artery and hence to its compliance. Phasic patterns of velocity in peripheral arteries have been recorded by using continuous wave ultrasound Doppler flowmeters coupled to high-speed spectrum analysers; this has enabled display of the stored spectral ensembles as 'sonograms'. Simultaneous recordings at proximal and distal sites in each limb of a variety of subjects were made under standard resting conditions; characteristic patterns of change in the sonogram are recognized where gross abnormalities of arterial anatomy are present. A technique is under development whereby the mean values of velocity for each 7.4 ms time slice are derived, smoothed, and the pulse described by standard Fourier transform analysis. The change of the waveform occurring during passage through the relevant arterial segment is then described by comparing the amplitude/frequency and time-delay/frequency plots at proximal and distal sites. Although results are at present preliminary, changes relating to age and known vascular abnormality are becoming apparent. Further development is in progress to determine the significance of these findings.