Impact of Mechanical Ventilation on the Developing Airway

Abstract

After completing this article, readers should be able to: 1. Explain why immature infants are at a greater risk for mechanical ventilation-induced airway damage than are more mature infants. 2. Describe the effect of ventilatory pressures on components of the airway. 3. Delineate how mechanical ventilation disrupts airway mechanics. 4. Characterize how mechanical ventilation affects immature airway smooth muscle. 5. Describe techniques of optimizing ventilation to minimize respiratory damage. Although the air passages take on a mature appearance well before a fetus is viable, they undergo significant maturational changes in late gestation. During development, the airways are more susceptible to damage. In fact, although controversy still surrounds the pathogenesis of bronchopulmonary dysplasia (BPD) and other neonatal airway complications, it appears that the duration and higher pressures of mechanical ventilation, along with the use of oxygen, are related to the development of airway-related problems in preterm infants. As a result, because of their greater need for ventilatory assistance, very preterm infants are at substantially increased risk of airway damage. With recent and continuing advancements in neonatal care, a growing number of immature infants survive premature births. One of the primary hurdles that must be overcome in these infants is respiratory system immaturity. In this context, an understanding of the embryologic development and physiologic maturation of the respiratory system is imperative. The respiratory system can be subdivided grossly into the airways and the lung parenchyma. Developmental changes in the mechanical properties of these two components predispose the immature airway to injury. The immature lung is a relatively noncompliant structure. During neonatal development, lung compliance increases with lung maturity. However, the opposite is true for airways. Immature airways are relatively more compliant than their mature counterparts, with airway maturation resulting in a decrease in airway compliance. This produces an interesting predicament when contemplating the administration of mechanical ventilation …