Trilogy breathing device

My husband is coming home from hospital tomorrow. He has COPD and was hospitalized for 19 days with pneumonia. He was on nighttime oxygen (2 liters) only. Now he will be on the same but 24hrs. The Dr. is adding a Trilogy breathing device at night. He is worried that we won't t know how to use it. My research indicates that it is easy to manage. Anyone have experience like ours?!