Expression of vascular escape: conductance or resistance?

Vascular escape is that phenomenon whereby a tachyphylaxis occurs in the vasoconstriction of an arteriole to a constant sympathetic stimulation. Vascular escape, in vivo, is primarily a blood flow event. Calculated resistance, as an index of vascular tone, does not consistently describe the responses of the arterioles undergoing vascular escape. Conductance, which is the inverse of resistance, obviates several of the errors produced by the use of resistance. In this study, we illustrate this issue using hypothetical and experimental data. Escape responses were calculated in terms of resistance and conductance and plotted against blood flow escape responses. Resistance escape responses were nonlinearly related to blood flow escapes and overestimated vascular escape with both hypothetical and experimental data. Conductance escape responses were linearly related to flow escape responses and consistently described vascular escape. We therefore conclude that conductance is a better index of vascular tone to express vascular escape.