High oxygen breathing improves inhomogeneities of ventilation-perfusion distributions in acutely injured lungs

Using twenty-five mongrel dogs either with or without alveolar flooding induced by oleic acid administration, the effects of high oxygen breathing (60% O₂) on ventilation-perfusion (V̇(A)/Q̇) distributions in the lungs were systematically investigated. V̇(A)/Q̇ distributions were examined by multiple inert gas elimination technique, from which the V̇(A)/Q̇ values describing mean positions of perfusion (Q̇) and ventilation (V̇(A)) distributions against the V̇(A)/Q̇ axis were calculated (mean Q̇ and mean V̇(A)). As the first measure of dispersion for V̇(A)/Q̇ distribution, the log standard deviation was estimated (log SD (Q̇) and log SD (V̇(A))). As the second measure of dispersion, the area under the curve, constructed by plotting inert gas arterial-to-alveolar partial pressure differences as a function of blood-gas partition coefficient, was calculated (aAD area). High oxygen breathing slightly enhanced the dispersion of V̇(A)/Q̇ distributions in the normal dogs but decreased that in the dogs injured with oleic acid. Therefore, we concluded that high oxygen breathing worsened the inhomogeneities of V̇(A)/Q̇ distributions in normal lungs but did improve those in acutely injured lungs.