Time-frequency analysis of laser Doppler flowmetry signals computed thanks to the S-transform on healthy subjects and on patients suffering from peripheral arterial occlusive diseases

A new time-frequency method based on the S-transform is presented to analyze the heart, respiration, myogenic, neurogenic and endothelial related metabolic activities on healthy subjects and on patients suffering from peripheral arterial occlusive diseases (PAOD). The analysis of the signal dynamics is presented at rest and during a local increase of temperature. The results show that five frequency bands, already known to correspond to the heart, respiration, myogenic, neurogenic and endothelial related metabolic activities, are clearly distinguishable. The dynamics observed on the patients are lower than on the healthy subjects. However, the heating increases the dynamic components of the two groups. The S-transform presents advantages that cannot be obtained with other time-frequency or time-scale representations.