Acute Respiratory Distress Syndrome (ARDS) is a pulmonary disease that afflicts approximately 200,000 people in the United States every year with a 40% mortality rate. ARDS causes reduced gas exchange throughout the body, resulting in hypoxia and a decline in metabolic processes. Mechanical ventilators are commonly used to treat the ailment, as it forcibly pushes air into the lungs. However, despite its short term benefits to a patient’s condition, it can have long term negative effects such as ventilator induced lung injury (VILI). VILI is caused by two phenomenon, known as volutrauma and atelectrauma. Volutrauma damages pulmonary airways and alveoli through overdistension, and atelectrauma harm these structures through repeated recruitment and derecruitment (RecDer). Both cause mechanical stress to epithelial cells in the alveoli, which reduces its viability. The goal of this study is to investigate the likelihood of RecDer as a function of airway collapsibility as modulated by the transmural pressure (Ptm) and orientation (θ). To do so, we develop a compliant airway model and compare its compliance characteristics (“tube law”) to that of pulmonary airways. Using this model, we create a pressure chamber to modulate the Ptm and θ. We study the instability through the measurement of the frequency of RecDer events that occur at a fixed flow rate. We find that as Ptm decreases and the angle of inclination increases, occlusion frequency rises. Furthermore, the instability frequency increases at a faster rate at higher angles of inclination. These studies can help researchers and clinicians by providing more insight into RecDer, VILI, ARDS, and their relationships.
