Spherical indentation of lungs: Experiments, modeling and sub-surface imaging

Knowledge of mechanics in atelectasis (alveolar collapse) and reinflation would be useful during anesthesia and critical care. Here an investigation is presented in which atelectasis is induced in a controlled manner on excised inflated lungs using spherical indentation, and noninvasive imaging of the deformed subsurface region is performed using optical coherence tomography (OCT). Indentation loads are physiologic, and spatial dimensions are far larger than alveolar size to allow continuum discussions. Experimental observations of atelectasis are compared with finite element model calculations of maximum stresses. Finally, atelectasis is compared during inflation of lungs with different gases (e.g., air, oxygen/anesthesia mixture).