This is a prospective pilot study. Targeted population include patients with COPD, non-oxygen dependent, with a baseline normal bicarbonate on previous lab (within 6 months of enrollment). Patients will be randomly selected to be part of the study sample. Recruitment will occur in both inpatient and outpatient settings. An email briefly explaining the objectives of the study will be sent to Internal Medicine residents and Pulmonary Critical Care fellows to help in patients' recruitment. Patients will be enrolled in the study only after being seen by Dr. Abdo or Dr. Allen. The study is expected to finish by the end of January 2017 or twelve months post IRB approval. Patients will be recruited and enrolled over six months, and the collected data will be analyzed six months after the last patient was included in the study. The study will target a study sample of 30 as detailed in the statistical analysis section, where patients will be their own control (3 months without HFNC followed by 3 months with HFNC).