Project Summary/Abstract This proposed project relates to the development and evaluation of a novel closed-loop long-term oxygen therapy control system that includes an innovative smartphone-based companion software application. We hypothesize that such a system will optimize oxygen delivery in mobile patients, minimize air hunger during physical exertion, avoid hyperoxia and improve patient quality of life. More than 1.5 million Americans are currently receiving long-term oxygen therapy. Drawbacks to long-term oxygen therapy include significant limitations to patient physical activity, a heightening of social isolation and impacts to emotional well-being. Improved mobile technology is needed to address these drawbacks and improve patient outcomes. A prototype system will be designed, built, and evaluated.