Comparing the effects of human hind limb massage by analysis of Laser Doppler Flowmetry and Photoplethysmography signal components using the wavelet transform

Non-invasive optical techniques, such as LDF (laser Doppler flowmetry) and PPG (photoplethysmography) are leading technologies to assess the human microcirculation. New mathematical strategies for signal processing such as WT (wavelet transform) have been developed to enhance its quantification capabilities. We have dedicated some effort to better understand the impact of massage therapy, a non-conventional technique used to relieve symptoms of vascular failure and improve functions, using these instruments. A group of 24 young healthy volunteers (19.9 ± 1.7 years old), both sexes, was submitted to two massage protocols applied in one limb, the other serving as control. Each protocol included three phases rest (I), massage (II), and recovery (III). LDF and PPG signals were obtained from both limbs and analyzed with the WT (p<0.05). A regional circulatory adaptation seems to take place during massage manoeuvres, affecting both test and control limbs detected with LDF and PPG. Some differences are noted regarding their oscillatory components, being clear that both sympathetic and myogenic components play a central role in the process. It is also clear that the simultaneous use of these two technologies seems to provide more detail and sensitivity in the analysis of the phenomena involved.