Effect of pressure support ventilation on the respiratory pattern variability

Mechanical ventilators are used to provide life support in patients with respiratory failure. We studied the effect of pressure support ventilation (PSV) on the variational activity of the respiratory pattern in 20 patients on weaning trials from mechanical ventilation. The patients were each placed under two different levels of pressure support ventilation. The respiratory pattern was characterized by the following time series: inspiratory time (T_j), breath duration (T_TOT), and tidal volume (V_T). The variational activity of breathing was partitioned into autoregressive, periodic and white noise fractions. High pressure support ventilation increased the gross variability of the inspiratory time and the breath duration. High PSV also caused a significant increase on the power of the oscillations for T_j and T_TOT time series. During both low and high PSV uncorrelated random behavior constituted > 80% of the variance of each breath component.