Cardio-respiratory Events in VLBW Preterm Infants During the Transitional Period: Clinical Features and Impact of Neonatal Characteristics.

Background Cardio-respiratory events (CRE), defined as intermittent hypoxic and/or bradycardic episodes, are very common among premature infants. The poor respiratory drive, together with the increased metabolic oxygen consumption and the reduced total blood oxygen carrying capacity of this population significantly enhance CRE frequency and severity.

Evidence from animal models has shown that CRE, either alone or combined to specific clinical factors (i.e., intrauterine growth restriction, support modality, need for supplemental oxygen etc.), can trigger oxidative stress, which may contribute to adverse neonatal outcomes. In particular, a significant association between CRE and the development of retinopathy of prematurity (ROP) has been largely established, with evidence of a positive correlation between ROP severity and CRE duration, depth of desaturation, and persistency after 3 to 5 weeks of age. A critical role for CRE on early brain development has also been suggested by several studies showing a relationship between the ensuing hypoxic burden and poor neurodevelopment from early infancy up to early school age. Eventually, a possible association between CRE severity and the development of bronchopulmonary dysplasia has been recently reported in very-low-birth-weight (VLBW) neonates.

Most of the available literature on CRE characteristics, physiological mechanisms and effects in the premature population, however, is based on infants aged 2-weeks or older, while data from the transitional period, defined as the first 72 hours after birth, are scarce.

The transitional period represents a critical phase of physiological adaptation and may affect several organ systems, most notably the heart and the lungs. In particular, the dynamic cardiovascular changes that characterize the transition from fetal to neonatal circulation may enhance preterm infants' cardiorespiratory instability, with possible effects on CRE characteristics. In turn, the hemodynamic and respiratory disturbances that characterize post-natal transition may exacerbate the clinical burden of CRE during this period, with possible clinical implications.

This study aims to characterize CRE during transitional periods in VLBW preterm infants, and to evaluate whether specific neonatal characteristics may have an influence on CRE type and severity.