The reproducibility of protocols used to mediate a current-induced vasodilation in the human cutaneous microcirculation

Introduction: Current-induced vasodilation (CIV) can be used to assess the prostacyclin (PGI2) pathway. This study, for the first time, evaluated the reproducibility of several protocols used to mediate a CIV. Methods: Three CIV protocols were evaluated in 10 healthy participants who completed four testing sessions. Two testing sessions were conducted on the calf, separated by a period of seven days allowing interday reproducibility to be assessed. Two testing sessions were also conducted seven days apart on the forearm. At each testing session, cutaneous microvascular assessments were conducted for one hour on the right limb of interest before assessments were immediately performed on the left limb, allowing for intersite, intraday reproducibility to be evaluated. Assessments were then repeated at the same site on the right limb, allowing for intrasite, intraday reproducibility to be evaluated. Reproducibility was assessed using the within-subject coefficients of variation and the intra-class correlation coefficients. Results: Protocol A (Pulses of 0.03, 0.06, 0.09, 0.12, 0.15, and 0.18 mA for 10 s each; 60 s intervals), Protocol B (0.1 mA for 60 s), and Protocol C (2 pulses of 0.1 mA for 10s each; 240 s interval) had good to excellent interday reproducibility for calf and forearm assessments. The intrasite, intraday reproducibility of each protocol was less clear. Intersite testing didn’t improve intraday reproducibility. Reproducibility was consistently unacceptable when the microvascular response to the electrical stimulation was expressed as the absolute change and the percentage change between baseline values and the maximal plateau. A microvascular response wasn’t induced ∼10% of assessments on either the calf or forearm. Conclusions: This study indicates that a CIV is most reproducible with interday testing and when data are expressed as the maximal plateau in perfusion units or as cutaneous vascular conductance, and as the area under the curve.