Representative CT scan of one animal at three different levels (apical, middle, basal). (a) Expiratory occlusion (10 cmH2O) before and after the recruitment maneuver. Lung volumes in this animal changed as follows: VHYP +1%, VNORM +15%, VPOOR +17%, VNON -30%, VGAS +11%. (b) Inspiratory occlusion at plateau pressure before and after the recruitment maneuver. Lung volumes in this animal changed as follows: VHYP +6%, VNORM +17%, VPOOR +26%, VNON -29%, VGAS +17%. VGAS, intrathoracic gas volume; VHYP, volume of hyperinflated lung parenchyma; VNON, volume of nonaerated lung parenchyma; VNORM, volume of normally aerated lung parenchyma; VPOOR, volume of poorly aerated lung parenchyma.