Fig. 1.

PEEP selection by EIT (Panel A and B): After a baseline phase lasting 20 min (PEEP_ARDSnet), a RM was performed (whose duration is shortened in the image for clarity purposes); end-expiratory lung impedance variation (∆EELI) was measured after 30 s (∆EELIstart) and after 10 min (∆EELIend); if ∆EELIend decreased more than 10% of ∆EELIstart, a new RM was performed, and PEEP increased by 2 cmH₂O. This was repeated until ∆EELIend decreased less than 10% of ∆EELIstart, or up to maximum PEEP level of 18 cmH₂O (PEEP_EIT). A new RM was performed and PEEP increased by 2 cmH₂O from PEEP_EIT (PEEP_EIT+2). Unstable EELI track (Panel C): an example of unstable EELI track