Wavelet analysis of oscillations in the peripheral blood circulation measured by laser Doppler technique

The wavelet transform technique, a time-frequency method with logarithmic f requency resolution, was used to analyze oscillations in human peripheral b lood flow measured by laser Doppler flowmetry. The oscillations extended ov er a nide frequency scale and their periods varied in time. Within the freq uency range studied, 0.0095-1.6 Hz five characteristic oscillations were re vealed, arising from both local and central regulatory mechanisms. After th e insertion of endothelium-dependent and endothelium-independent vasodilato rs the spectra of blood flow markedly differed in the frequency interval 0. 0095-0.02 Hz. In this way it was demonstrated that endothelial activity is a rhythmic process that contributes to oscillations in blood flow with a ch aracteristic frequency of around 0.01 Hz. The study illustrates the potenti al of laser Doppler flowmetry combined with dynamical systems analysis for studies of both the micro- and macroscopic mechanisms of blood flow regulat ion in vivo.