Spectral analysis of laser Doppler skin blood flow oscillations in human essential arterial hypertension.

The aim of this study was to investigate whether human essential arterial hypertension (EHT) is associated with modification of the skin blood flowmotion (SBF), which could be a sign of skin microcirculatory impairment. Forearm skin perfusion was measured by laser Doppler flowmetry (LDF) in conventional perfusion units (PU) before and after ischemia in 20 middle-age newly diagnosed EHT untreated patients, in 20 middle-age long standing EHT treated patients and in 30 age and sex matched healthy normotensive subjects (NS). Power spectral density (PSD) of SBF total spectrum (0.009-1.6 Hz), as well of five different frequency intervals (FI), each of them 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) or cardiac (0.6-1.6) activity, was also measured in PU(2)/Hz before and after ishemia, using Fourier analysis of LDF signal. The three studied groups did not differ in basal and post-ischemic skin perfusion or in basal SBF parameters considered. However, while a significant post-ischemic increase in PSD of total spectrum SBF (P < 0.001) and of its different FI, with the only exception of respiratory FI, was observed in NS, a significsnt post-ischemic increase in PSD was observed only for total spectrum (P < 0.01) and for endothelial FI (P < 0.001) in newly diagnosed EHT patients and only for myogenic FI (P < 0.05) in long standing EHT patients. These findings suggest that the mechanisms which mediate the post-ischemic increment of SBF are perturbed earlier in human EHT than the mechanisms which mediate the skin post-ischemic hyperaemia. The same findings also suggest that the impairment of the endothelial mechanism involved in SBF control occurs by the time in the course of EHT.