Post-ischaemic peak flow and myogenic flowmotion component are independent variables for skin post-ischaemic reactive hyperaemia in healthy subjects

The aim of this study was to clarify whether the post-ischaemic amplification of skin blood flowmotion (SBF) influences the extent of skin post-ischaemic hyperaemia. Forearm skin perfusion was measured by means of laser Doppler flowmetry (LDF) and forearm SBF was examined using Fourier analysis of LDF signal, under basal conditions and following forearm ischaemia in 50 healthy subjects. Power spectral density (PSD) of SBF total spectrum (0.009-1.6 Hz), as well of the frequency intervals (FI) related to endothelial (0.009-0.02 Hz), sympathetic (0.02-0.06 Hz), myogenic (0.06-0.2 Hz), respiratory (0.2-0.6 Hz) and cardiac (0.6-1.6 Hz) activity was measured in PU(2) (LDF perfusion unit)/Hz. Multiple regression analysis evaluated whether post-ischaemic peak-flow, as an indicator of shear stress, or post-ischaemic SBF independently affected the post-peak-flow hyperaemia calculated as corrected area under the LDF curve (C-AUC). Following ischaemia, we observed a statically significant increase in skin perfusion (from basal of 11.7+/-5.8 PU to peak flow of 62.3+/-41.4 PU, p<0.0000005) and in PSD of SBF total spectrum (p<0.01) as well of the different FI considered (p<0.005 for the endothelial and myogenic FI; p<0.05 for the sympathetic, respiratory and cardiac FI) compared to baseline. Multiple regression analysis showed that peak flow and post-ischaemic SBF component of myogenic origin were significant independent variables for the C-AUC (p=0.0000001 and p=0.009, respectively). These findings suggest that not only increased shear stress but also post-ischaemic amplification of myogenic SBF component independently contributes to the more prolonged phase of post-ischaemic skin re-perfusion in healthy subjects.