Fig. 1.

Imaging variables obtained at baseline, after 1 h of ventilation with no positive end-expiratory pressure (PEEP), and following a recruitment maneuver in ventral and dorsal slices of a representative rat. ³He density maps (A); maps and frequency distribution histograms of regional fractional ventilation (FV) (B); and maps and frequency distributions of apparent diffusion coefficient (ADC) for ³He (C). Both FV and ADC increased at 1 h and returned to lower values after recruitment. Spreading of frequency distributions indicates higher FV heterogeneity at 1 h.