Computerised automated algorithm

The reactive hyperaemia index (RHI), a measure of endothelial function, was calculated using measurements from a peripheral arterial tonometry (PAT) device placed on the tip of each index finger (Endo-PAT2000, Itamar Medical, Caesarea, Israel). The PAT device applies uniform pressure to the surface of the distal finger, allowing for measurement of pulse volume changes in the finger [27 (link)]. Baseline pulse amplitude was measured from each fingertip for 5 minutes. Arterial flow was interrupted for 5 minutes by a cuff placed on a proximal forearm (Hokanson AG101, D.E. Hokanson Inc., Bellevue, WA, USA) at whichever occlusion pressure was higher between 200 mm Hg and 60 mm Hg plus systolic blood pressure. Pulse amplitude was recorded electronically in both fingers and analysed by a computerised, automated algorithm (Itamar Medical) that provided the average pulse amplitude for each 30-second interval after forearm cuff deflation for up to 5 minutes. To evaluate the vascular response in relation to baseline, with adjustment for systemic effects and skewed data, the hyperaemic response was expressed as the natural logarithm of the ratio of post-deflation to baseline pulse amplitude in the hyperaemic finger divided by the same ratio in the contralateral finger, which served as a control.