Fig. 2
Method of setting time-controlled adaptive ventilation, a protocol using APRV mode with specific settings. a Typical time-controlled adaptive ventilation (TCAV, previously referred to as personalized airway pressure release ventilation or P-APRV) airway pressure and flow curves. Correctly set TCAV has a very brief release phase (TLow—time at low pressure) and CPAP phase (THigh—time at high pressure) [8]. The THigh is ~ 90% of each breath. The two other TCAV settings are the pressure at inspiration (PHigh) and at expiration (PLow), which is always programmed as 0 cmH2O. TLow is sufficiently brief such that end-expiratory pressure (PLow) never reaches 0 cmH2O measured by the tracheal pressure (green line). b Alveolar stability is maintained 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 studies have shown that if the end-expiratory flow (EFT;− 45 L/min) to the peak expiratory flow (EPF;− 60 L/min) ratio is equal to 0.75, the resultant TLow (0.5 s) is sufficient to stabilize alveoli [12, 13]. The lung with ARDS collapses more rapidly such that the EFT/EPF ratio of 75% identifies an expiratory duration of 0.45 s as necessary to stabilize alveoli. Figure and figure legend reproduced and modified from Jain et al. 2016 with permission [14]