Pediatric emergency medicine trisk 0232 0232

initiated. Expansion of the lungs increases the neonate’s PaO2 and pH, which
causes pulmonary vasodilation and a subsequent fall in pulmonary vascular
resistance. The initial breaths taken by the infant must inflate the lungs and effect
a change in vascular pressures so that the lung water is absorbed into the
pulmonary arterial system and cleared from the lung. This inflation pressure is a
powerful mechanism for the release of pulmonary surfactant, which increases
compliance of the lung and establishes functional residual capacity.
Full alveolar development and sufficient surfactant production is not complete
until 34 weeks’ gestation. Prior to 23 to 24 weeks’ gestation, there is a lack of
surfactant and terminal airways have not developed, therefore resuscitation prior
to 23 to 24 weeks is rarely successful outside of a controlled neonatal intensive
care environment.