I like to walk 4 miles a day but it drops my O2 level down to the mid 80's or lower. Usually lower. Dr. said put the bottle on #4 but that doesn't help much. Am I messing myself up? I was just recently given the COPD diagnoses, put on oxygen, sent home, but no info on what I can and cannot do. Actually no info at all. Tucson VA. Don't want to roll over here. Thanks.