The effects of 50% oxygen on the resolution of pulmonary injury.

We studied the effects in dogs of long-term inhalation of 50% oxygen on an 8-day course of pulmonary injury caused by intravenous oleic acid. After lung injury, the experimental animals were placed in an environmental chamber where the inspired oxygen fraction (FIO2) was maintained at 0.5 (N = 12) or 0.21 (N = 12). Oleic acid caused a marked increase in venous admixture and a decreae in PaO2, which persisted at about the same concentration for 3 days after injury. These variables gradually returned toward preinjury values at 8 days. There was no significant difference in the clinical course, gravimetric lung water measurements, or lung histologic findings between oxygen-treated and air-breathing control animals. We concluded that 50% oxygen does not affect either the extent or resolution of lung injury induced by a sublethal dosage of oleic acid.