Effects of transpulmonary and vascular pressures on rate of pulmonary edema formation

The effect of transpulmonary pressure (Ptp) on rate of extravascular fluid accumulation in isolated canine left lower lobes perfused at constant vascular pressures was investigated. Changes in rate of extravascular fluid accumulation were estimated by changes in rate of slow weight gain. Mean inflow pressure (Ppa) was constant at 34 cm H₂O. Mean outflow pressure (Ppv) was constant at either 27.2 cm H₂O or 13.6 cm H₂O. When increasing Ptp is associated with a derecruitment of vascular beds as the lung changes from predominantly zone III toward zone II, or zone I, there is a decrease in rate of weight gain. When increasing Ptp is not associated with a derecruitment of vascular beds, it is impossible on the basis of these experiments to predict the change in rate of weight gain.