Quantitative Morphometry and Local Tissue Elasticity Measurements in a Rat Model of Ventilator-Induced Lung Injury

<bold>Introduction:</bold> Mechanical ventilation can induce or worsen pre-existing lung injury, known as ventilator-induced lung injury (VILI). We assessed alterations in structure and mechanical elasticity of bleomycin-injured and healthy lungs in response to VILI. <bold>Methods:</bold> Lungs of 12 controls (Con.) and 8 bleomycin (Bleo.) instilled rats were scanned using synchrotron based propagation based phase-contrast CT (PBI) (2µm resolution), in 5 Con. and 4 Bleo. rats VILI was induced by high tidal volume ventilation for 20 min. 3D morphological features were extracted with a dedicated image processing pipeline. Adjacent lung slices were obtained by guided sectioning to perform picrosirius red histological staining followed by atomic force microscopy (AFM) to assess the elasticity of lung tissue. <bold>Results:</bold> Fig. 1a shows a 3D representation of local pore size on µ-CT data. The mean airspace/pore size was higher in Bleo. than in Con. lungs (p<0.0001) (Fig. 1b) and VILI increased pore size significantly in both cases. <fig><object-id>erj;64/suppl_68/PA3395/F1</object-id><object-id>F1</object-id><object-id>F1</object-id><graphic></graphic></fig> Fig. 1c depicts the spatial correlation between the PBI, histopathology, and AFM data. VILI resulted in stiffening of lung parenchyma in Con. but not in Bleo. rats. However, it reduced stiffness in consolidated regions in Bleo. rats(Fig. 1d). <bold>Conclusion:</bold> Correlative morphometry and AFM revealed that Con. were more sensitive to VILI than Bleo, suggesting a reduced local strain in overall stiffer Bleo-VILI lungs.