What Causes COPD In A Non Smoker?

In November I was having chest pains and shortness of breath. Angina was diagnosed and problems showed up on my chemical stress test. A chest Xray was done and both lungs were cloudy. No fever, or sore throat. Heart cath came back minimal blockage with no intervention necessary. However spirometry was very bad and I was diagnosed with COPD. I have never smoked but by late husband did 5 packs a day. apulse Ox is at 93 so how can it be COPD with pulse ox at 93 and pulse at 52 reading?