Variability of Peripheral Arterial Tonometry in the Measurement of Endothelial Function in Healthy Men

Measurement of endothelial function using peripheral arterial tonometry (PAT) has been reported to be significantly correlated with coronary blood flow. Repetitive PAT measurements were performed in 22 healthy mate subjects at test intervals of 1 hour (5 times within a day) and 0.5 hours (7 times within a day) to evaluate the variability of the reactive hyperemia index (RHI). A total of 10 subjects underwent additional repetitive PAT at 2 hour intervals (7 times within a day) for 3 consecutive days to evaluate the diurnal effects and day-to-day reproducibility. The RHI from each test was computed automatically based on a 15 minute recording of pulse wave amplitude changes of the fingers in response to reactive hyperemia induced by a 5 minute occlusion of the brachial artery. Intrasubject variability of RHI at different test intervals, defined as the coefficient of variation (CV) was 15.3% +/- 5.3%,16.1% +/- 7.8%, and 22.6% +/- 3.9% for the tests at 0.5 hour, 1 hour, and 2 hour intervals, respectively. Reactive hyperemia indices measured at the same time points on each of the 3 days were not statistically significant. The interday reproducibility, presented as intraclass correlation coefficients (lCC) ranged from -0-07 to 0.47. We conclude that repetitive PAT measurements have no carryover effect on RHI at 1 hour, and 2 hour intervals, and the RHI measured at 0.5 hour intervals is associated with a trend of increase. The interday reproducibility is relatively low and the intrasubject variability of RHI is similar to those observed in studies of flow-mediated dilation using brachial artery ultrasound scanning.