This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Symptoms of insomnia and daytime somnolence affect 25-50% of individuals with chronic obstructive pulmonary disease (COPD) and have a negative association with general and respiratory-specific quality of life in COPD. Prior research has shown that the risk of obstructive sleep apnea is not increased in COPD, but sleep quality is impaired with a greater number of sleep stage transitions and arousals, especially as COPD progresses. Nocturnal oxygen therapy as been the primary treatment for impaired sleep in COPD if hypoventilation and hypercarbia are not present, but oxygen therapy has not been shown to improve sleep quality or other outcomes, including mortality. This research proposal seeks to better understand the causes of sleep fragmentation in COPD and introduces a new device that might improve sleep in COPD. In this research, we aim to 1) better understand the role of increased inspiratory resistance during sleep to cause sleep disruption and hypoventilation and 2) seek to understand whether nocturnal nasal insufflation (NNI) may improve sleep quality and ventilation in COPD by alleviating changes in inspiratory resistance. With sleep onset, there is a decrease in neuromuscular tone of the upper airway dilator muscles. In normal individuals, this results in an increase in inspiratory resistance that is compensated by increasing inspiratory time. However, because of the expiratory flow limitation that is characteristic of COPD, COPD patients may be unable to compensate for increased inspiratory resistance and might be more susceptible to sleep disruption. NNI delivers heated, humidified air at rates up to 20 L/min via an open nasal cannula. NNI has been shown to generate small amounts of positive air pressure in individuals with sleep apnea and improve inspiratory flow limitation. Preliminary results in COPD patients also show an improvement in inspiratory flow and ventilation, but the effects on sleep architecture are unknown. In this protocol, we will enroll 45 individuals with all stages of COPD in a research protocol that will allow us to assess the normal sleep and breathing patterns in COPD as well as to determine the effects of NNI and oxygen on breathing during sleep. Upon enrollment, individuals will have their sleep-wake cycle evaluated by actigraphy for a period of one week. Following this, they will undergo a baseline polysomnogram (PSG) to evaluate sleep and breathing. A second PSG will be performed to evaluate the effects of oxygen and NNI at variable flow rates on ventilation during wakefulness and sleep.