Investigating alveolar mechanics and collapse via spherical indentation and in‐situ sub‐surface observation

Abstract

Understanding of alveolar mechanics is important for respiratory physiology, pathology, and clinical anesthesia. In this study, we performed spherical indentation tests on excised mammalian lung lobes to explore alveolar stiffness and collapse. The experimental apparatus allowed force‐displacement data, and in‐situ microscopic observation of alveolar collapse and recovery under quantified applied stresses. Lungs were subjected to inhalation environments of air, 100% oxygen, and small amounts (0.2%) Isoflurane (IsoF), in different orders. Salient results of our studies include the following: 1) Inhalation of oxygen immediately increases lung stiffness and alters alveolar collapse distribution significantly; 2) Re‐opening of collapsed alveoli is strongly dependent on inhaled environment; 3) When the lung was inflated with air, then oxygen (3 tidal volumes) then air, the apparent effects of oxygen on lung mechanical properties were highly reversible. This data, coupled with preliminary experiments on isolated pulmonary surfactant under different environments, support our hypothesis that inhaled gases significantly, immediately and (sometimes) reversibly affect surfactant properties, and provide further evidence that damage associated with oxygen inhalation may be importantly associated with surfactant disruption.