Can venous occlusion plethysmography be used to measure high rates of arterial inflow?

To investigate whether venous occlusion plethysmography (VOP) may be used to measure high rates of arterial inflow associated with exercise, venous occlusions were performed at rest, and following dynamic handgrip exercise at 15, 30, 45, and 60% of maximum voluntary contraction (MVC) in seven healthy males. The effect of including more than one cardiac cycle in the calculation of blood flow was assessed by comparing the cumulative blood flow over one, two, three, or four cardiac cycles. The inclusion of more than one cardiac cycle at 30 and 60% MVC, and more than two cardiac cycles at 15 and 45% MVC resulted in a lower blood flow compared to using only the first cardiac cycle (P < 0.05). Despite the small time interval over which arterial inflow was measured (~1 s), this did not affect the reproducibility of the technique. Reproducibility (coefficient of variation for arterial inflow over three trials) tended to be poorer at the higher workloads, although this was not significant (12.7 +/- 6.6, 16.2 +/- 7.3, and 22.9 +/- 9.9% for the 15, 30, and 45% MVC workloads; P = 0.102). There was also a tendency for greater reproducibility with the inclusion of more cardiac cycles at the highest workload, but this did not reach significance (P = 0.070). In conclusion, when calculated over the first cardiac cycle only during venous occlusion, high rates of forearm blood flow can be measured using VOP, and this can be achieved without a significant decrease in the reproducibility of the measurement.