Oxygen During Postnatal Stabilization

KEY POINTS

• 1.

  There is a precisely controlled sequence of circulatory and respiratory changes at birth that leads to the establishment of adult-type circulation and airborne respiration.

• 2.

  Despite the well-established sequence of events, 1 in 10 infants, particularly those born before term, will require interventions to achieve an adequate postnatal adaptation.

• 3.

  Oxygen has been widely accepted as the most relevant drug for preterm resuscitation.

• 4.

  There is a need to achieve oxygen saturation between 80% and 85% within the first 5 minutes after birth in very preterm infants <32 weeks’ gestation) independently of the initial fraction of inspired oxygen.

• 5.

  We need continued and critical appraisal of both the need for and the doses (concentrations) of oxygen administered during resuscitation.

Introduction

Fetal-to-neonatal transition in mammals is characterized by a precise sequence of circulatory and respiratory changes that contribute to the establishment of adult-type circulation and airborne respiration. As a consequence, there is an abrupt increase in the oxygen availability that fulfills the increased energy requirements of multicellular organisms. Despite the exquisite physiologic arrangements that regulate this sequence of events, almost 10% of all newly born infants, and especially those born prematurely, require resuscitative interventions to achieve an adequate postnatal adaptation. In the newborn period, resuscitation requires lung expansion, reducing pulmonary resistance, improving lung compliance, and achieving a functional residual capacity. All these changes improve alveolar capillary gas exchange and arterial blood oxygenation.

The lungs, the thoracic cage, and respiratory muscles mature late in gestation. Moreover, surfactant and the antioxidant enzymatic and nonenzymatic defenses, especially in males, are not readily available until the last weeks of gestation. Hence preterm infants, especially very preterm infants with a gestational age (GA) below 32 weeks, frequently experience difficulties establishing effective respiration immediately after birth. Immaturity and surfactant deficiency lead to uneven lung ventilation with hyperventilated areas coexisting with atelectasis and the inability to establish a functional residual capacity. As a consequence, the premature baby is at increased risk of developing hypoxemia, hypercapnia, and increased work of breathing, which are characteristic of respiratory distress syndrome with hypoxemic respiratory failure. Therefore prenatal interventions such as the administration of antenatal steroids and postnatal resuscitation with positive pressure ventilation and oxygen supplementation constitute essential interventions necessary to overcome respiratory insufficiency.

Oxygen has been widely accepted as the most relevant drug for preterm resuscitation. However, there are still important aspects regarding its use in the immediate postnatal period that have not yet been answered. It is necessary to address the optimal initial fraction of inspired oxygen (Fi o ₂ ), oxygen saturation (Sp o ₂ ) target ranges in the first minutes after birth, and how to titrate oxygen according to the infant’s response. Of note, oxygen in excess leads to hyperoxemia and direct tissue damage secondary to oxidative stress, activation of proinflammatory and proapoptotic pathways, and other mechanisms. At the other extreme, hypoxemia, especially when combined with bradycardia, significantly enhances the risk for intraventricular hemorrhage (IVH) and death. Both situations increase mortality and/or short- to long-term morbidities in survivors.

The aim of the present chapter is to critically analyze the most relevant and recent literature concerning the use of oxygen in the delivery room (DR) to help neonatologists optimize the care management of preterm infants during postnatal stabilization.