Effect of end-expiratory airway pressure on accumulation of extravascular lung water.

The effect of end-expiratory airway pressure on the accumulation of extravascular lung water during lobar venous occlusion for 2 h was studied in closed-chest artifically ventilated dogs. Dogs were divided into two groups by end-expiratory airway pressures of 0 or 10 cmH2O. High-pressure lobar pulmonary edema was produced by lobar venous occlusion, which elevated microvascular hydrostatic pressure. After occlusion of the lobar pulmonary vein, lobar venous pressure (and microvascular hydrostatic pressure) rapidly became identical to pulmonary arterial pressure. We measured extravascular lung water (post mortem) and pulmonary arterial pressure and calculated plasma colloid osmotic pressure to determine the relationship between the accumulation of lung water and the difference between pulmonary microvascular pressure and plasma colloid osmotic pressure (net intravascular filtration pressure). At comparable net intravascular filtration pressures, dogs ventilated at the higher end-expiratory airway pressure accumulated more extravascular lung water. This study indicates that increasing end-expiratory airway pressure from zero to 10 cmH2O increases the accumulation of extravascular lung water when microvascular hydrostatic pressure is raised.