Nasal cannulas are medical devices used when people are unable to get sufficient oxygen to keep their body functioning optimally, whether that's due to a condition like chronic obstructive pulmonary disease (COPD), another respiratory disorder, or an environmental change. Nasal cannulas (and the oxygen sources they connect to) are lightweight, easy to use, and affordable. They may be used in a variety of hospital settings, at home, or on-the-go.