Fig. 2
From: The 30-year evolution of airway pressure release ventilation (APRV)
Method of setting expiratory duration (TLow). a Typical personalized airway pressure release ventilation (P-APRV) airway pressure and flow curves. Correctly set P-APRV has a very brief release phase (time at low pressure—TLow) and CPAP phase (time at high pressure—THigh) [6]. The THigh is ~90 % of each breath. The two other P-ARPV settings are the pressure at inspiration (PHigh) and at expiration (PLow). TLow is sufficiently brief such that end-expiratory pressure (PLow) never reaches 0 cmH2O measured by the tracheal pressure (green line). b Maintain alveolar stability by adaptively adjusting the expiratory duration as directed by the expiratory flow curve. The rate of lung collapse is seen in the normal (slope 45°) and acutely injured lung (ARDS, slope 30°). ARDS causes a more rapid lung collapse due to decreased lung compliance. Our preliminary studies have shown that if the end-expiratory flow (EEF; −45 L/min) to the peak expiratory flow (PEF; −60 L/min) ratio is equal to 0.75, the resultant TLow (0.5 s) is sufficient to stabilize alveoli [54, 55]. The lung with ARDS collapses more rapidly such that the EEF/PEF ratio of 75 % identifies an expiratory duration of 0.45 s as necessary to stabilize alveoli. Thus, this method of setting expiratory duration is adaptive to changes in lung pathophysiology and personalizes the mechanical breath to each individual patient