Clinical physiology and functional imaging
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Clin Physiol Funct Imaging · Nov 2003
Comparative Study Clinical Trial Controlled Clinical TrialQuantification of inspiratory-induced vasoconstrictive episodes: a comparison of laser Doppler fluxmetry and photoplethysmography.
Laser Doppler fluxmetry (LDF) or photoplethysmography (PPG) are frequently used as non-invasive tools to assess skin blood flow. They are both thought to be suitable and interchangeable methods for the detection of sympathetically activated vasoconstrictive episodes that can be provoked by a voluntary deep inspiration (DI), the so-called inspiratory gasp response (IGR). However, a rigorous comparison of the two methods has not been reported in the literature. ⋯ Overall correlation of IGR amplitude detected with LDF and PPG was significant (r=0.433). Surprisingly, there was a continuous increase of the correlation coefficient from the first (r=0.105) or second (r=-0.184) IGR to the fifth (r=0.727) IGR. This implies that experimental data obtained with PPG and LDF are not equivalent and that one has to be cautious regarding the comparison and interpretation of results obtained with these two different methods.