Regional distribution of tidal cyclic collapse. Tidal changes in nonaerated tissue (tidal recruitment) in diaphragmatic slices between a nondependent region of interest (ROI) and a dependent ROI during airway pressure release ventilation (APRV) with or without spontaneous breathing (+SB/-SB). Data presented as the percentage (mean ± standard error of the mean) of the total lung volume (gas and tissue) of voxels for each ROI. §§§P < 0.001, dependent ROI versus nondependent ROI. ¶P < 0.05, APRV +SB versus APRV -SB. *P < 0.05 between ventilatory groups (post hoc results given only if significant).