Variations in the severity of retinopathy seen in newborn rats supplemented with oxygen under different conditions of hyperbarism.

The purposes of this experimental study were to evaluate the effects of oxygen supplementation delivered under hyperbaric conditions on the retinas of newborn rats and to determine the minimum and maximum levels of hyperbarism capable of protecting the retinal vessels from the toxic effects of oxygen without determining lethal effects in this experimental model. A control group of newborn rats were maintained with their mother for the first 12 days of life under room-air conditions. A second group of animals were exposed to a hyperbaric environment (+81 kPa) under normoxic conditions for the first 7 days of life and subsequently returned to normobaric conditions for the next 5 days. Examination of the retinal flat mounts from this latter group of animals revealed essentially normal vascular networks with only a modest degree of vasoconstriction. Two other litters of ratlings, with their mothers, were given supplemental oxygen at an FiO2 of 80% under a compression pressure of +101.25 kPa. In this group of animals, death of both of the mother rats from pulmonary edema occurred on the first day of treatment, and, in spite of immediate mother substitution, the newborn rats succumbed to the same complication. Five other groups, each containing two litters of newborn rats with their mothers, were exposed to FiO2s of 80% at hyperbaric levels ranging from +20.25- to +81.0 kPa for the first 7 days of life. On the eighth day, the FiO2s were reduced to 21%. After 5 days of room-air recovery, the animals were killed.(ABSTRACT TRUNCATED AT 250 WORDS)