64 - Pulmonary Gas Exchange in the Developing Lung

Abstract

Integral to the system of pulmonary gas exchange are mechanisms to maintain matching of pulmonary perfusion and alveolar ventilation, so-called ventilation/perfusion matching. The goal is that alveolar oxygen and pulmonary capillary blood have intimate contact to optimize diffusion of O2 and CO2. Requisite features of the efficient gas-exchange apparatus include sustained effective ventilation to replenish the oxygen stores in alveolar gas, free diffusion of both oxygen and carbon dioxide across the alveolar-capillary barrier, and sustained blood flow through the capillaries. However, the newborn infant is particularly vulnerable to the development of arterial hypoxemia. The mechanisms for maintaining the matching of alveolar ventilation (V_A), ̇usually referred to as V, and pulmonary perfusion (Q_P), usually referred to as Q, and the factors and diseases that influence changes in the intrapulmonary distribution of V and Q and thereby the matching of V to Q (V/Q matching) in neonates are the topics of this chapter. Given that bronchopulmonary dysplasia is the most common comorbidity of preterm birth, we will highlight how BPD influences V/Q matching and how various ventilation strategies affect V/Q matching in BPD.