Fig. 4. Comparison of methods for evaluating positive end-expiratory pressure (PEEP) recruitment. The quasi-static compliance method, evaluated with tidal volumes of 400 ml (quasi-static compliance [CqST], VT400) and 700 ml (CqST, VT700), underestimated alveolar recruitment compared with the pressure-volume (P-V) curve method. Recruitment was compared with two PEEP levels. ** P < 0.01 between the two methods (with both tidal volumes of 400 and 700 ml) and * P < 0.05 between the two tidal volumes by the quasi-static method, by one-way analysis of variance and Bonferroni post hoc analysis.