To determine the utility and sensitivity of the lung clearance index (LCI) technique as a marker of small airways disease in adults with chronic lung conditions compared to healthy adults, adjusting for age, sex and smoking status.

Target Population and Enrollment. The study will recruit and consent 300 patients from our Occupational Medicine and Interstitial Lung/Rheumatology Clinics at National Jewish Health who have been referred for evaluation of chronic lung conditions. 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. Inclusion criteria for the group with chronic lung disease will include physician diagnosis of a chronic lung condition (e.g. bronchiolitis, pulmonary fibrosis, asthma, coal mine dust lung disease, asbestosis), and age ≥18 years. 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. Study participation will consist of one visit that will last between 90-120 minutes. The chronic lung disease group will fill out the informed consent and complete both LCI testing and spirometry. The healthy control group will complete informed consent, a brief questionnaire, LCI testing, and spirometry.

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.

Symptomatic military deployers with deployment-related lung disease seen at National Jewish Health and healthy controls subjects.