OSCE
PREFINAL OSCE Pathophysiology An uninjured healthy lung contains an intact respiratory epithelial layer and alveolar space patrolled by resident alveolar macrophages. Type I and type II pneumocytes contribute to regulation of alveolar contents, including surfactant, and maintain the integrity of the alveolar-capillary barrier. Following infection or inj ury, an influx of innate immune cells such as neutrophils and monocytes migrate from the circulation into the interstitial and alveolar spaces, • During respiratory distress, damage to the epithelial and endothelial layers results in breakdown of the alveolar-capillary barrier and accumulation of edematous fluid and debris in the alveolar spaces. Pro-inflammatory and destructive functions of alveolar macrophages, monocytes, and neutrophils co ntribute to disease pathology. • The consequence is the loss of alveolar-capillary barrier function. This disruption permits the accumulation of proteinaceous fluid in the alveolar space coupl