Lung mechanics. In the second series of experiments the ventilation strategies RM5, noRM and RM60 were applied to mice ventilated with low V T and a PEEP of 6cmH 2 O, to find out whether the impairment of lung mechanics during ventilation with noRM and RM60 could be prevented by a higher PEEP (Fig. 9 ). Ventilation with RM5 at a PEEP of 6 cmH 2 O (PEEP6_RM5) showed stable lung functions. Ventilation without RM (PEEP6_noRM) resulted, notwithstanding the increased PEEP, in a strong decrease in C during the first 180 min of ventilation until a plateau was reached at about 30% of the initial C. Correspondingly R, G and H increased and finally doubled in this group. Also ventilation with RM60 (PEEP6_RM60) did not suffice to keep lung functions entirely stable at a PEEP of 6 cmH 2 O. Although the decrease in C between the RMs was relatively moderate, the initial C was not maintained over six hours. R, in contrast, returned to the initial value after each RM. In line with this, lung impedance measurements revealed a moderate increase in H, but not in G after six hours. All three groups differed significantly from each other regarding C, R, H and G, except from the parameters measured in the PEEP6_RM60 group directly after the RM. R aw and hysteresivity were not different between the groups and R aw remained at baseline in all experiments (data not shown).