Reversal of cardiopulmonary failure during active sleep in hypoxic kittens: implications for sudden infant death.

Experimentally induced hypoxia in kittens precipitated episodes of depressed respiration and irregular cardiac function during quiet sleep, waking, and transitional states. The onset of active sleep stimulated both breathing and heart rate and decreased abnormal variability in these functions. However, hypoxia markedly reduced the proportion of active sleep. These data suggest that active sleep protects against respiratory and cardiac abnormalities in infants. Chronic hypoxemia or other factors that reduce active sleep in infants, including the normal developmental decrement in this state, may increase the risk of cardiopulmonary failure and death.