Arterial stiffness is suggested to be a replacement method to measurements of brachial diameter following the release of an ischemic stimulus. We tested this hypothesis by comparing resting large [C1] and small [C2] arterial stiffness (as well as total peripheral resistance [TPR]) with brachial flow mediated dilation (FMD, indicator of endothelial function). Furthermore, the anatomical location that C2 represents is unclear. Could this reflect microcirculatory changes? We tested this hypothesis by comparing C2 with concurrent microcirculatory responses.

29 subjects (aged 18 to 30 years) were investigated. A tonometer recorded the radial blood pressure; pulse waveform analysis (PWA) was used to calculate C1, C2 and TPR. These parameters were correlated with forearm FMD responses. FMD was taken as the % maximal change in brachial arterial lumen diameter following cuff release and measured by B-mode ultrasound. Microcirculatory parameters included finger flux measured by Laser Doppler Fluxmetry [LDF]; pulsatile finger volume measured by photoplethysmography [PPG] and palm skin temperature measured by infrared thermography [Tpalm].

FMD linearly related to C1 (r = 0.4, P = 0.04), but not C2 (P > 0.05). Comparison of arterial stiffness against microcirculatory responses revealed a weak relation between C2 and %PPG (r = 0.38, P = 0.07), but no relations were found for C1 (P > 0.05). For TPR, a linear relation was found with %PPG (r = 0.50, P = 0.01) and %Tpalm (r = 0.59, P < 0.001). No other correlations were evident (P > 0.05).

Small arterial stiffness (C2) is neither a viable marker for endothelial function nor of microcirculatory responses. The findings show that sonographically assessed brachial FMD is the better method for endothelial function testing.