sal678,
You have to remember that COPD can change in a matter of seconds. One second you are feeling fine, the next you can't breathe. Your 6-minute walk test was done in a controlled environment. Clean air and probably air conditioned. Very little if any allergens or air particulates that irritate your lungs. Two days later, you go for a walk. Now you are subject to all kinds of outdoor irritants. Pollen, dust and dander, ozone, wind, heat or cold, etc. It makes a huge difference in your ability to be able to breathe and exercise or walk at the same time. You are not alone in this. All COPD sufferers are in the same boat. I always check the air quality before I go outside for any amount of time. Knowing what causes me breathing problems helps in the evaluation of air quality. Hope this helps a little. Take care and God Bless!