Lung tissue (HE original magnification ×400). A: in the control group, the alveolar interval was normal, and there was no inflammatory cell; B: in the BUD group, slightly inflammatory cell infiltration and mild alveolar interstitial edema were found; C: in the VILI group, part of alveoli were ruptured, and there were diffuse pulmonary interstitial edema and inflammatory cell infiltration.