The effects of regional lung differences in alveolar mechanics on the transpulmonary pressure-volume (Ptp-V) relationship and the single-breath washout (SBW) of nitrogen were investigated by mathematical modeling and postmorten human lung experiments. Regional nonuniformity in alveolar collapse and re-opening were associated with differences in gravitational stress or elasticity. Model simulations predict that neither type of regional nonuniformity qualitatively affects the shape of the Ptp-V curve, but does affect the terminal (or small-volume) portion of the SBW. Comparisons of characteristics of the Ptp-V and SBW curves indicate that regional nonuniformity in alveolar collapse is an important mechanism associated with ventilation inhomogeneity.
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Ackno&dgement-This researchw as supportedin part by theM edicalR esearchS erviceo f theV eteransA dministration, NIH grantA M 08305U, nited Torch Serviceso f Cleveland, andC ysticF ibrosisF oundationD. uringp arto f thisr esearch, R.B.S. was supported by a NIH Predoctoral Traineeship (GM-01090).