Fig. 3

Ventilator-induced lung injury (VILI) in the microenvironment arises through a permeability-originated obstruction response (POOR) that is self-reinforcing (POOR-becomes-POORer). A In normal homogeneously ventilated lung, alveoli (hexagons) are uniformly open and stress is evenly distributed. B Isolated POOR areas of edema-filled or collapsed alveoli (center) that occur in early lung injury concentrate stress in adjacent patent alveoli, causing overdistension and instability. C The size of the POOR area expands due to collapse and flooding of surrounding alveoli, leading to the POOR region becoming POORer. D As the size of the POORer region expands, the stress applied to the surrounding alveoli is amplified and, unless this pathogenesis is interrupted, tissue damage secondary to VILI will continue to spread rapidly. (Permission to republish requested)