Development, anatomy, and physiology of the lungs

Abstract

Because of the anatomic proximity of the upper airway and gastrointestinal (GI) tracts, there is a risk of lung injury through aspiration. A number of lines of defense counter penetration of gastric acid or meals into the airways, including laryngeal closure, swallowing apnea and cough. Nonetheless, the prevalence of aspiration is greatly increased in a number of chronic diseases including chronic cough, asthma, interstitial lung diseases, lung transplantation and others. A causal relationship between these disorders and aspiration is not established, neither is there a clear benefit to treating aspiration. In part, this relationship may be difficult to prove due to limitations in detection of aspiration. This chapter focuses on systems of protection against aspiration, methods to detect aspirations of meals into the upper and lower airways, common pulmonary disorders associated with increased risk of aspiration and responses of normal lung tissue to acidification of the distal esophagus.