Final answer:
A CPAP mask can be used to deliver oxygen to a client who requires long-term oxygen therapy and is adequately oxygenated at a lower flow.
Step-by-step explanation:
A client who requires long-term oxygen therapy and is adequately oxygenated at a lower flow can use a CPAP mask to deliver oxygen. A CPAP (Continuous Positive Airway Pressure) device is commonly used for sleep apnea treatment, where a mask covers the nose or nose and mouth and forces air into the airway at regular intervals, keeping it open. This pressurized air helps the client to breathe more easily and maintain proper oxygenation levels.