Unilateral lung edema: effects on pulmonary gas exchange, hemodynamics, and pulmonary perfusion distribution

Two types of unilateral lung edema in sheep were characterized regarding th eir effects on pulmonary gas exchange, hemodynamics, and distribution of pu lmonary perfusion. One edema type was induced with aerosolized HCl (0.15 M, pH 1.0) and the other with NaCl (0.15 M, pH 7.4). Both aerosols were nebul ized continuously for 4 h into left lungs. In HCl-treated animals, pulmonar y gas exchange deteriorated [from a partial arterial O-2, pressure-to-inspi red O-2, fraction ratio (Pa-O2/FIO2) of 254 at baseline to 187 after 4 h HC l]. In addition, pulmonary artery pressure and total pulmonary vascular res istance increased (from 16 to 19 mmHg and from 133 to 154 dyn.s.cm(-5), res pectively). In NaCl-treated animals, only the central venous pressure signi ficantly increased (from 7 to 9 mmHg). Distribution of pulmonary perfusion (measured with fluorescent microspheres) changed differently in both groups . After HCl application, 6% more blood flow was directed to the treated lun g, whereas, after NaCl, 5% more blood flow was directed to the untreated lu ng. HCl and NaCl treatment both induce an equivalent lung edema, but only H Cl treatment is associated with gas exchange alteration and tissue damage. Redistribution of pulmonary perfusion maintains gas exchange during NaCl tr eatment and decreases it during HCl inhalation.