Exploring Ventilator-Induced Lung Injury: A Comprehensive Ex-Vivo Study Using Phase-Contrast MicroCT and Atomic Force Microscopy

Mechanical ventilation (MV) can induce or exacerbate ventilator-induced lung injury (VILI), particularly in mechanically heterogeneous lungs with pre-existing injury. We investigated VILI in a rat model of bleomycin-induced lung injury and compared it with healthy controls using a combined in-vivo and ex-vivo imaging approach. Previously acquired in-vivo data from four-dimensional (4D) phase-contrast synchrotron micro-computed tomography (microCT) and forced oscillation measurements showed increased lung elastance and reduced local acinar strain in bleomycin-induced injured lungs at baseline and after injurious MV. To identify structural and mechanical correlates, we performed automated three-dimensional (3D) pore analysis and atomic force microscopy (AFM) on formalin-fixed, paraffin-embedded lung tissue, complemented by histology and spatial co-registration. Ex-vivo analysis revealed pronounced airspace enlargement after injurious MV of healthy lungs, whereas this effect was attenuated in fibrotic lungs. AFM demonstrated region-specific mechanical responses, and correlation analyses linked pore geometry and nanoscale stiffness to in-vivo lung mechanics. Spatial analysis further showed colocalization of VILI-associated airspace damage with injured regions. Overall, extracellular matrix remodelling modifies the lungs mechanical response to injurious MV. This multiscale correlative approach provides mechanistic insight into the interplay between lung injury and VILI and informs ventilation strategies in structurally altered lungs.