Fig. 1
Experimental protocol and correlation between changes in lung volume by computed tomography (CT) and electrical impedance tomography (EIT) related data. A Experimental protocol of a representative case. Traces of airway pressure (upper row), impedance change in non-dependent (middle row) and dependent (lower row) lung regions during the study timeframe are shown. Two levels of PEEP were applied in random order (in this representative case, first low-PEEP and then high-PEEP, after a recruitment maneuver). At both PEEP levels, end-expiratory and end-inspiratory holds were applied to obtain positive end-expiratory pressure and end-expiratory lung impedance (EELI), and airway plateau pressure and end-inspiratory lung impedance (EILI), respectively. The impedance change (ΔZ) corresponded to the difference between EILI and EELI. CT and EIT assessments were performed at the same time. B Linear correlation between delta end-expiratory lung volume (ΔEELV) CT-measured and the change of lung volume obtained from changes in end-expiratory lung impedance (ΔEELIml)