Reference ranges for SpO2, respiratory rate, and tidal volume in term newborn infants after birth: a narrative review

Background and Objective: Post-natal adaptation implies respiratory and hemodynamic changes that contribute to the successful switching from transplacental to lung-based respiration and from serial to parallel circulation after cord clamping. Initial respiratory efforts extrude lung fluid to the interstitial space, facilitate alveolar aeration, and alveolar-capillary gas exchange contributing to an increase in the arterial partial pressure of oxygen (paO2). Consequently, there is a decrease in pulmonary vascular resistance and the closure of the intra-and-extracardiac shunts. The establishment of a functional residual capacity contributes to the stabilization of the respiratory rate (RR) and the arterial paO2. This study sought to update the reference ranges for respiratory function, oxygen saturation, and heart rate (HR) to guide neonatologists in the stabilization and/or resuscitation of newborn infants in the delivery room (DR). Methods: Data on the respiratory function and oxygenation pattern of normal term infants in the stabilization period during the first minutes after birth were retrieved and stored by employing continuous pre-ductal pulse oximetry and respiratory function monitoring. The electronic databases searched included MEDLINE, Embase, CINAHL, and Scopus. Statistical methods were employed to establish the percentile curves for each parameter. Key Content and Findings: We provide data of HR and oxygen saturation measured by pulse oximetry and RR and tidal volume (VT) measured by a respiratory function monitor and recorded during the first 10 minutes after birth in healthy term infants. Post-natal respiratory and cardiorespiratory adaptation in healthy term babies is enhanced by delayed cord clamping. HR and oxygen saturation achieved values of 140–160 bpm and 90–95% in the first 2–3 minutes after birth, respectively, and a VT and RR between 5–10 minutes. Conclusions: Updated reference ranges for clinical parameters in the DR constitute a useful tool for guiding neonatologists in the stabilization of newborn infants.