Decreased respiratory tolerance from intermittent asphyxia in rat sucklings.

To study the respiratory tolerance of rat pups to intermittent asphyxia induced by exposure to closed rebreathing, we randomized newborn rats from four litters into two treatment groups. Respiratory tolerance was defined as the time interval during asphyxia until the first episode of 30 seconds of apnea. Rats in the experimental group were asphyxiated once daily during the first 4 days of life. Rats in the control group were asphyxiated once on day 4 of life. Pups exposed to intermittent asphyxia had a significant reduction in respiratory tolerance compared with that of littermates asphyxiated once at the same age. These findings suggest that the ability of the young mammal to withstand re-exposure to asphyxia may be impaired.