I have stage 3 COPD I use oxygen at night and on any exertion . I'm 78 years old. About 4 or 5 years ago I was diagnosed with PAD. For the last couple of years the testing has been negative for that. I do a slow walk on a treadmill 20 minutes a day at 1.2 speed . I can only go maybe 5 to 7 minutes before my calves really ache so bad that I have to stop and then I start up again after a little rest, Which is the symptoms of pad but my tests are clear from that. The length of walking and the pain in the leg is always the same . My oxygen fluctuates from 88 to 94 when I'm doing that short walk without using my oxygen . Sometimes it'll stay in the low 90s. But I still get the hurting in my leg . I am wondering if anybody else with COPD has that same problem.