Effects of acute cold exposure on carotid and femoral wave intensity indexes: evidence for reflection coefficient as a measure of distal vascular resistance.

Our aim was to investigate the effects of acute cold pressor test (CPT) on augmentation index (AI) and wave intensity (WI) indexes from right common carotid artery (RCCA) and right common femoral artery (RCFA) and to test whether the reflection coefficient (RC) from wave intensity analysis can reflect the distal vascular resistance (DVR) accurately. Forty-three healthy males were randomly selected for measurements at baseline and 1 min after CPT at RCCA or RCFA. CPT induced similar increases of heart rate and blood pressure in RCCA and RCFA groups with their pulse pressures unchanged. The W(2) (the second peak of WI) was too obscure in RCFA to be analyzed. The W(1) (the first peak of WI) of both arteries, W(1)-W(2) (interval between W(1) and W(2)), and NA (negative area between W(1) and W(2), indicating reflected waves) of RCCA and the R-W(1) (interval between the R wave of ECG and W(1)) of RCFA decreased obviously, whereas the W(2) and R-W(1) of RCCA and the RC (calculated as NA/W(1)) of RCFA increased with no changes in the RC of RCCA and the NA of RCFA during CPT compared with baseline. The AIs from both arteries increased significantly after CPT. These results suggested that acute CPT has opposing effects on cerebral and peripheral vascular resistances, with the former decreased and the latter increased. The RCs from RCCA and RCFA are more associated with the changes of cerebral and peripheral vascular resistances, respectively, than the NA and AI, and the RC is of guiding value in assessing DVR.