Lung recruitability determines the impact of PEEP on mechanical power in ARDS

Absolute mechanical power increases with higher PEEP, but power per aerated lung decreases when PEEP produces substantial recruitment. PEEP-induced increases in absolute power do not necessarily imply a higher mechanical load per alveolar unit. Recruited volume and compliance changes are the main physiological determinants of this effect. Among bedside tools, the R/I ratio best identifies whether and to what extent PEEP will reduce or increase mechanical power per alveolar unit.