Utility of Lung Clearance Index Score as a Noninvasive Marker of Small Airways Disease

Inclusion Criteria: * physician diagnosis of a chronic lung condition (e.g. bronchiolitis, pulmonary fibrosis, asthma, coal mine dust lung disease, asbestosis), and age ≥18 years. The healthy control group will comprise 300 volunteers who are at least 18 years of age, have no history of pre-existing lung disease, and report no respiratory illness in the four weeks preceding enrollment Exclusion Criteria: * Exclusion criteria will include recent myocardial infarction, stroke, eye surgery, chest/abdominal surgery (within past month), known thoracic, aortic, or cerebral aneurysm, or uncontrolled hypertension.