Detection of physiological singularities in respiratory dynamics analyzed by recurrence quantification analysis of tracheal sounds

Following a previous analysis that was performed on lung sounds of right and left apexes [Chaos, Solitons & Fractals 2004;21:869–77], in the present paper we studied tracheal sounds by recurrence quantification analysis, adding chaos analysis as estimation of correlation dimension and Lyapunov spectrum. The results confirm the presence of singularities indicating that respiratory dynamics is controlled by a discrete non-deterministic dynamics based on violation of Lipschitz conditions. On the basis of the results, it is also evidenced the possibility to introduce new indexes having interest in respiratory diagnostic routine.