Intensity-dependent effect of pulsed and continuous therapeutic ultrasound on endothelial function: a randomised crossover clinical trial

Abstract

Background/Aims The aim of this study was to evaluate the effects of different intensities and waveforms of therapeutic ultrasound on endothelial function in typically healthy participants. Methods A total of 15 participants were evaluated over 2 consecutive days. Different intensities of continuous and pulsed (20% duty cycle) 1-MHz ultrasound were applied to the brachial artery for 5 minutes each. Endothelial function was measured using flow-mediated dilation technique before and immediately after ultrasound was applied. Results Compared to baseline values, endothelium-dependent vasodilation increased with both continuous (2.8%) and pulsed (1.6%) ultrasound at an intensity of 0.4 W/cm2SPTA. At 1.2 W/cm2SPTA, endothelium-dependent vasodilation was 4.1% above baseline for pulsed and 5.3% above baseline for continuous waveforms. There was no additional increase in vasodilation at intensities above 1.2 W/cm2SPTA. The percentage of endothelium-dependent vasodilation was similar for the all of the different waveforms studied. Conclusions Both continuous and pulsed ultrasound waveforms promote endothelium-dependent vasodilation. There was a dose-dependent increase in vasodilation at intensities from 0.4 W/cm2SPTA to 1.2 W/cm2SPTA. Pulsed is more efficient than continuous ultrasound because it produces the same effect on endothelium-dependent vasodilation while employing 20% of the energy applied with continuous ultrasound.