Cardiorespiratory instability during sleep in infants: Physiological and developmental consequences

Abstract During fetal life, autonomic control of the cardio‐respiratory system undergoes rapid maturation and this continues after birth during the first year of life. This underlying immaturity of cardio‐respiratory control leads to an increased risk of cardio‐respiratory instabilities and resultant hypoxaemia during infancy. In infants born preterm, the risks of cardiovascular instability, apnoea resulting in profound hypoxaemia and even death are significantly greater than those born at term. In the neonatal unit, oximeters and cardio‐respiratory monitors are set to long averaging times to reduce frequent false alarms due to movement artefacts; thus, only long apnoeas of prematurity (>20 s) or apnoeas associated with sustained oxygen desaturations or bradycardia are detected. However, the majority of apnoeic events and the apnoeas associated with periodic breathing are much shorter than this (<10 s), with only brief or very mild desaturations, and currently remain largely clinically undetected and therefore untreated. There is now growing evidence that postnatal intermittent cerebral hypoxia can affect developmental outcomes and also cardiovascular control. This narrative review will report recent findings which add to a growing literature suggesting short apnoeas and periodic breathing are not benign and the accompanying desaturation and re‐saturation may contribute to adverse outcomes, particularly in preterm infants.