Study flowchart.

Ten animals were studied during volume-controlled ventilation during ventilation with 5 ml/kg (baseline) and 10 ml/kg tidal volume (V_T) (measurement time point 1) in the normal lung (NL) as well as after induction of acute lung injury (ALI) (time point 2) at inspired fractions of oxygen of 0.5 and 1.0, respectively. Then a constant low-flow inflation maneuver (pressure-volume (PV) maneuver) was performed and positive end-expiratory pressure (PEEP) was set 2 cm H₂O above the lower inflection point (LIP) identified in the PV curve. Using a crossover design, further measurements were performed 5 and 30 min after ventilation with low V_T and active interventional lung assist (ILA) and after another 5 and 30 min with high V_T and inactive ILA (no ILA) (time points 3–6). Five animals were randomly ventilated in the reversed chronological order. Ventilator settings of V_T and PEEP at each measurement time point are shown in the lower part of the Figure. *, time elapsed after the change in ventilator and ILA settings.