Objective: Apnoea, bradycardia and hypoxemia occur frequently in extremely preterm infants, yet there is little longitudinal data describing cardiorespiratory development in these infants. This prospective study characterized early age-dependent changes in cardiorespiratory function and determined how activity is affected by factors such as underlying disease, postnatal insults and therapeutic interventions.
Patients and methods: Thirty-three infants born between 23 and 28 weeks gestational age (GA) were monitored weekly from birth to beyond term-equivalent age (i.e. 25-45 weeks postconceptional age, PCA). Baseline cardiorespiratory activity as well as apnoea/hypopnoea, bradycardia and hypoxemia events were examined using impedance pneumography, electrocardiography (ECG) and pulse oximetry, respectively.
Results: Three hundred thirty-eight cardiorespiratory recordings lasting 3236 h were analysed. While the respiratory rate (RR) did not change during the early postnatal period, heart rate (HR) decreased and O2 saturation improved. There were 5973 total cardiorespiratory events, and their incidence decreased with advancing age. However, they still occurred frequently at term-equivalent age and after hospital discharge (mean PCA at discharge=38.3+/-0.5 weeks). Moreover, infection significantly increased apnoea/hypopnoea and hypoxemia incidence.
Conclusion: The persistence of cardiorespiratory events beyond term-equivalent age as well as the marked impact of infection on cardiorespiratory function indicate that close surveillance after hospitalization is of crucial importance in extremely preterm infants.