P8.12 CAROTID ARTERY WAVE INTENSITY ANALYSIS IN HEALTHY HUMANS DURING EXERCISE

Abstract

Background: The study of wave reflections in the carotid artery may reveal the vasoactive response of the cerebral circulation to exercise, which is not yet fully characterised. Therefore, we aim to examine the effect of exercise on wave intensity parameters measured in the carotid artery of healthy humans, using non-invasive wave intensity analysis. Methods: Ultrasound measurements of right common carotid diameter and flow velocity were obtained from 8 healthy male athletes (27 ± 4 y). Two measurements were taken at rest, followed by measurements during 5-min incremental steps of cycling at 0%, 20%, 40%, 60% and 70% of the subjects’ peak workload, then eight measurements during post-exercise recovery. Wave speed (c) and the intensity peaks and energies of Forward Compression (FCW), Backward Compression (BCW) and Forward Expansion (FEW) waves were determined and compared between the three stages. The reflection index (RI) is calculated as RI=BCW/FCW. Results: All parameters increased, following the increase of workload. At end of recovery, all parameters returned to rest values. During exercise, c increased by 200%. The intensity of FCW, BCW and FEW increased by 600%, 1100% and 600% during exercise; likewise the energy increased by 450%, 500% and 800%, respectively. Also, RI increased during exercise by 170%. Conclusions: RI results indicate that cerebral resistance increases with increased workload. Also, the increase of FEW magnitude suggests that an increase in exercise workload is associated with a greater cardiac muscle speed of deceleration in late systole.