Figure 3.
Pressure-induced alveolar expansion. Cross-sectional area data for alveolar air pressures (Palv) of 5 and 15 cm H2O. Lines connecting data points at different Palv are inflation curves, with slopes indicating degree of pressure-induced alveolar expansion. Solid circles, before induction of single-alveolar edema model. Open circles, after induction of edema model. (A) Data for cross-sectional area (Aedem) of the alveolus that became liquid-filled. All four data points were obtained in the same alveoli (n = 11, from nine different lungs). (B) Data for cross-sectional area (Aadj) of the alveolus adjacent to the one that became liquid-filled. All four data points were obtained in the same alveoli (n = 13, from eight different lungs). (C) Aadj data for a representative individual alveolus. Combining all data in the air-filled lung before liquid-filling an alveolus: inflation increased alveolar cross-sectional area A from 7.0 ± 0.6 × 103 μm2 by 23% ± 2%, and alveolar perimeter length L from 3.2 ± 0.1 × 102 μm by 8% ± 1% (P < 0.01, n = 24). *Area greater at Palv of 15 than 5 cm H2O (P < 0.01), for either control air-filled state or edema model. #Area different in edema model than air-filled state, at constant Palv (P < 0.01). ##Area different in edema model than in air-filled state, at constant Palv (P < 0.02). ‡Slope less in edema model than in air-filled state (P < 0.01), indicating decreased compliance.