(A–C) Representative confocal images of mouse (A), human (B), and pig (C) alveoli are shown at low (left images) and high magnification (right images). Images were obtained at the indicated inflation pressures. The low-magnification images are pseudocolored differently for the different inflation pressures. The merge image was obtained by superimposing the green and red images. The superimposition reveals yellow pseudocolor at a nondistending alveolar segment (solid rectangle) but separation of red and green at the distending segment (dashed rectangle). Images were centered for superimposition. An AM is located at the corner of the nondistending alveolar segment (arrow). High-magnification images of rectangles are below. (D) Bars show hyperinflation-induced alveolar diameter increase at sites of alveolar distension in 4 lungs each for mouse, human, and pig. Findings were replicated in at least 3 alveoli in each lung. (E) Bars show numbers of AMs at distending and nondistending locations of alveoli in 4 lungs each for mouse, human, and pig. Each dot represents data for 1 lung. Data analyses. Group data are mean ± SEM. P values were calculated by 1-way ANOVA with Bonferroni’s correction (D) or paired t test (E).