I was diagnosed with moderate copd back in March/April time. A that time my O2 levels were 99 even though I was smoking. Since then I'm nearly 4 months quit BUT yesterday I went to an assessment appointment for pulmonary rehab and my O2 levels were only 93!! I don't feel ill or have a cold etc but I do get SOB very easily. Can anyone give me an idea of what is going on please??