Physiological measurements of transition and resuscitation at birth

Abstract

The neonatal transition is characterized by major physiological changes in respiratory and hemodynamic function, which are predominantly initiated by breathing and clamping of the umbilical cord. Lung aeration leads to the establishment of functional residual capacity, allowing pulmonary gas exchange to commence. This triggers a significant decrease in pulmonary vascular resistance, consequently increasing pulmonary blood flow and venous return. Clamping the umbilical cord contributes to these hemodynamic changes by altering the cardiac preload and increasing peripheral systemic vascular resistance. The resulting changes in the systemic and pulmonary circulations influence blood flow through both the oval foramen and ductus arteriosus. This eventually leads to closure of these structures and the separation of the pulmonary and systemic circulations. Most of our knowledge on human neonatal transition is based on human (fetal) data from the 1970s and extrapolation from animal studies. However, there is renewed interest in performing measurements directly at birth. By using less cumbersome techniques, (n.b. and probably more accurate), our previous understanding of the physiologic transition at birth is challenged, as well as the causes and consequences for when this transition fails to progress. This thesis provides an overview of physiological measurements of the respiratory and hemodynamic transition at birth.