I'm on O2 when active. I don't use it when I'm sitting at home or sleeping. Thank you jean

If you just use the FEV1 of 25%, that's very severe, according to the GOLD, ATS and COPD Foundation standards. However, all standards use more than just the FEV1 to "stage" the disease. They also look at the number of exacerbations in the last year and to some extent how well the patient is able to function independently. Also, remember, the "staging" is really for docs who aren't necessarily pulmonologists. It's designed to help them figure out where their patients are in the disease progression and help them determine appropriate treatments, meds, etc. Unlike cancer, where stage 4 cancer is usually terminal, very severe COPD can be stable for years. It does not portend your imminent demise!