Ambulatory Oxygen Therapy for Individuals With Mild-to-moderate Interstitial Lung Disease

Inclusion Criteria: * Individuals with fibrotic ILD (all sub-groups of ILD) who have normal oxygen saturation at rest (SpO2 \> 90%) but develop exertional hypoxemia as demonstrated by a SpO2 = 80-89% with activity (measured during 6MWT). Exclusion Criteria: * Use of home oxygen therapy within the previous year for the management of ILD, co-morbid conditions that may require oxygen therapy (such as COPD, cardiovascular disease, or other illnesses), or individuals that require the use of non-invasive ventilation. Additionally, individuals with significant cardiovascular, metabolic, neuromuscular or any other disease that could contribute to dyspnea or abnormal cardiopulmonary responses to exercise will be excluded. Individuals with musculoskeletal injuries that prevent them from completing cycle ergometry exercise trials and ambulation will also be excluded. Individuals with peripheral vascular disease will be excluded from measurement of vascular function (flow mediated dilation).