Respiratory Mechanics and Gas Exchange: The Effect of Surfactants
The purpose of the lung is to exchange gases, primarily oxygen and carbon dioxide, between the atmosphere and the circulatory system. To enable this exchange, the airways in the lungs terminate in some 300 million alveoli that provide adequate surface area for transport. A common lung defect is the dysfunction of a complex mixture called pulmonary surfactant that is found in a thin layer of fluid coating the alveoli. This is a leading cause of respiratory distress syndrome (RDS), a well-known condition that affects premature infants and adults, and results in mortality rates ranging from 10% to 60% depending on patient age. The main goal of this work is to further the understanding of pulmonary surfactants to improve treatments and consequently decrease the high morbidity that accompanies RDS. To do so, we develop a mathematical model to study the action of pulmonary surfactant and its determinative contributions to breathing. The model is used to explore the influence of surfactants on alveolar mechanics, gas exchange and microscale work of breathing. Using the model, we can also examine the role that individual surfactant components such as phospholipids, proteins and cholesterol play during breathing. This provides insight into the design of exogenous pulmonary surfactants for clinical applications to treat RDS.