Analysis of stationarity and statistical changes in myographic signals from respiratory muscles

Spectral analysis of myographic signals from respiratory muscles is a promising non-invasive technique to study respiratory diseases. However, it requires that the signal be at least weakly stationary. Electromyographic (EMG) and vibromyographic (VMG) signals are related to electrical and mechanical activity, respectively. Local stationarity of the signals from an accessory respiratory muscle is evaluated by means of the reverse arrangement test. A methodology for change detection and to analyze the evolution of the stationarity during the respiratory cycle in myographic signals is also presented. These studies are performed in healthy subjects and patients with chronic obstructive pulmonary disease. Local stationarity decreases with the increase of the level of ventilation and when a maintained exercise goes forward. High levels of ventilation and respiratory muscle fatigue produce statistical changes in myographic signals