Noninvasive pulsed Doppler blood velocity measurements and calculated flow in human digital arteries

Few quantitative studies of blood velocities and calculated flow measurements in the human digital arteries have been reported due to resolution limitations of existing Doppler instruments. Under carefully controlled conditions, we transcutaneously measured blood flow velocities in the ten digital arteries in the right hand of five male adults (BSA 1.83-2.19m2) with a high resolution 20MHz pulsed Doppler instrument which was calibrated in vitro. A 1.0mm2 ultrasonic transducer was mounted on a 16 gage needle in a stereotaxic apparatus at a known Doppler angle to the vessel flow axis. The sample volume (SV) was adjustable in both range (1 - 13 mm) and length (0.3 - 4.0 mm). In order to obtain a more uniform acoustic field in the SV, the transmitted pulse was attenuated exponentially at a rate consistent with acoustic attenuation in blood. This permitted measurement of velocity profiles and spatially averaged velocities along the sound beam. Deconvoluted calculations of vessel internal diameter (D) and volume flow rates (Q) were made in the 10 different digital vessels. Velocity waveforms were triphasic with positive diastolic flow. In the digital vessels, the average D varied from 0.78 +/- 0.11 to 1.04 +/- 0.05 mm and the average Q from 2.03 +/- 0.92 to 3.71 +/- 0.69 ml/min. For each vessel, Q correlated with body surface area r = 0.80 to 0.91 (p less than .05) with a coefficient of variance calculated from the normalized flow rate (Q/BSA) ranging from 10% to 38%. Flows in parallel vessels of the middle digits were not significantly different. These studies suggest that noninvasive, spatially averaged blood velocity and calculated flow measurements, which are accurate and reproducible, can be made in human digital arteries.