The present invention describes a method and apparatus for detecting and quantifying intrinsic positive end-expiratory pressure (PEEPi) of a respiratory patient breathing with the assistance of a ventilator. A processing device receives respiratory airway data from one or more sensors adapted to non-invasively monitor a respiratory patient, calculates from the respiratory airway data two or more parameters that are indicative of or quantify intrinsic positive end-expiratory pressure of the patient, and generates an indication intrinsic positive end-expiratory pressure (PEEPi).
