ABSTRACT
Fetal to neonatal transition is characterized by a precise sequence of circulatory and respiratory changes that leads to the establishment of an adult type circulation and airborne respiration. Consequently, there is an abrupt increase in the oxygen availability to tissue to fulfill the increasing energy requirements. Despite the exquisite arrangements of this sequence of events, almost 10% of all newly born infants, and especially those born prematurely, will require interventions to achieve an adequate postnatal adaptation. In the newborn period, resuscitation means fundamentally expanding the lung, facilitating pulmonary circulation by reducing pulmonary resistance, and achieving a functional residual capacity. All these changes will enhance alveolar capillary gas exchange and arterial blood oxygenation. Traditionally, pure oxygen was employed as gas admixture to ventilate the lungs. In the recent years, resuscitation with air has been recommended for asphyctic term and near term infants based on meta-analyses that have reported a significant reduction in mortality in babies resuscitated with air versus 100% oxygen. However, the initial inspired fraction of oxygen needed for stabilization of the preterm yet constitutes a matter of debate. Extremely preterm infants frequently need oxygen supplementation in the first minutes after birth to avoid hypoxemia. Moreover, those preterm infants who don't achieve oxygen saturations around 80% in the first five minutes after birth are at greater risk of death and/or intraventricular hemorrhage. The present chapter aims to shed light on this intriguing conundrum.
