Studying the development of transcutaneous blood gas levels (tcpO2 and tcpCO2) and the sleep apnea profile in relation to sleep states in normal preterm infants between 36 and 52 weeks postconceptual age we found a dynamic increase in tcpO2 during regular breathing (without apnea) and a steady decrease in tcpCO2 during both regular and periodic breathing. The mean tcpO2 of periodic breathing, however, persistently remained well below the corresponding level found during regular breathing. It is suggested that in normal preterm infants there is a continued maturational adjustment of autonomic respiratory control up to 3 months post term and, furthermore, that periodic breathing may persistently be associated with a relative hypoxemia.
