Effect of elevated vascular pressure transients on protein permeability in the lung

Neurogenic pulmonary edema (NPE) may develop in individuals with head trauma or seizures and is generally thought to have a hydrostatic basis in the severe degree of pulmonary hypertension that occurs. Recently, it has been suggested that vascular pressures may rise to levels that damage the vessels, leaving the patient at risk for further edema development. The objective of this study was to determine if pulmonary vascular protein permeability is increased in a canine isolated perfused left lower lung lobe (LLL) preparation by pressure transients that may occur in NPE. Venous pressure (Pv) was transiently raised to values ranging from 8 to 102 Torr in 19 LLL. One Pv transient was studied per LLL. After Pv was returned to normal, the osmotic reflection coefficient (sigma d) for total proteins was determined by the hematocrit-protein double indicator technique. No reduction in sigma d was observed until microvascular pressure exceeded 70 Torr. The average sigma d for the 11 LLL in which the peak microvascular pressure was less than 70 Torr was 0.74 +/- 0.03 (SE). Above this level sigma d fell linearly with increasing Pv, with a value of 0.26 being observed after the highest Pv transient. These results suggest that protein permeability may increase in patients with NPE who develop very large increases in pulmonary vascular pressures but may not be a universal occurrence in this disorder.