Analysis of pulmonary vascular interdependence in excised dog lobes.

The pressure-volume behavior of intraparenchymal extra-alveolar arteries and veins was measured at various lung inflation states by inflating and deflating the vasculatures with air. The vascular volumes at specific vascular pressures (Pv) and transpulmonary pressures (Ptp) were partitioned into components of axial length and cross-sectional area. An analysis of the interrelationships between the perivascular pressure (Px), the vascular pressure vs. cross-sectional area behavior, and the Ptp is presented. For in vivo values of Pv, at functional residual capacity, the vascular-parenchymal mechanical interaction was small and values of arterial and venous Px approximately Ppl. With increasing Ptp to 30 cmH2O, values of both the arterial and venous Px relative to Ppl (Px - Ppl) decreased to approximately -5 cmH2O, indicating that the magnitude of the vascular-parenchymal interaction with increasing Ptp is similar for both arteries and veins in the in vivo state. At any fixed Ptp, values of arterial and venous Px - Ppl decreased nearly linearly with decreasing vascular cross-sectional area. These results were generally consistent with a linear continuum elasticity solution relating stress and deformation in the perivascular parenchyma.