Synchrosqueezing to investigate cardio-respiratory interactions within simulated volumetric signals

The interest of volumetric signals measured by respiratory inductive plethysmography is twofold: (1) clinical as their measurement is non-invasive and (2) physiological as they reveal the interactions between the cardiac and respiratory systems. Interestingly these signals may be seen as the addition of non-stationary cardiac and respiratory modes ordered in frequency. This feature makes them particularly suitable for time-frequency representation based on the pursuit of modes like Synchrosqueezing (SQ). As a preliminary to an application to real cardio-respiratory (CR) signals, a simulated approach has been chosen because of the availability of a reference signal which allows both the validation of the approach and the fine-tuning of the parameters of the algorithm used. Notably, the number of modes necessary to reconstruct the cardiac component from the decomposition of the whole CR signal was analyzed and might be limited to 6. So, this paper aims at investigating the functioning of SQ on one simulated CR signal and comparing its performance with the one of an already tried and tested approach: Empirical Mode Decomposition. In the present set-up, it turns out that the two approaches provide equivalent results.