Correlation of changes in oxygenation, lung water and hemodynamics after oleic acid-induced acute lung injury in dogs

Changes in oxygenation after oleic acid (OA)-induced acute lung injury were correlated to changes in extravascular lung water (EVLW) and hemodynamics in 19 mongrel dogs. Three patterns seemed apparent. In group 1 (seven dogs) EVLW increased by 88% from control values but Pa(O₂) fell only 15%. The change in Pa(O₂) in this group was related directly to the change in mixed venous O₂ tension (P(V̄O₂)) after the OA-induced fall in cardiac output. In group 2 (eight dogs), EVLW rose by 120% and PaO₂) fell 53%, 90 min after OA administration. In this group, there was a subsequent spontaneous improvement of Pa(O₂) to 75% of control values, without any measured change in EVLW. In group 3 (four dogs), the fall in Pa(O₂) was comparable to that of group 2, but the increase in EVLW was greater (148%) and there was no spontaneous improvement in oxygenation. Cardiac index fell in all three groups. A small but significant increase in P(V̄O₂) partially explains the improvement in oxygenation in group 2. We conclude that changes in oxygenation are a poor index of injury during this model of acute lung injury and that the course of oxygenation is directly related to measured changes in EVLW and hemodynamics.