The primary analysis will include all recruited patients, irrespective of their Body mass index. Changes in transpulmonary pressure before and after Xenon wash-in will be assessed with the Wilcoxon signed-rank test for matched pairs. Center of Ventilation Index and Global Inhomogeneity Index, which will be assessed at three time points, will be compared with the use of repeated measures ANOVA with the post-hoc Sidak test.