Preliminary data show that in COPD patients, HFT substantially decreases ventilatory demand during sleep. The central hypothesis of this proposal is that lowering ventilatory demand using nasal high-flow therapy during sleep will elevate lung function, reduce dyspnea on exertion and improve quality of life. Thus, this proposal aims will determine the effects HFT over time on 1) lung function; 2) dyspnea on exertion; and 3) quality of life.