what are the early signs and symptoms of copd?
['Shortness of breath, especially during physical activities.', 'Wheezing.', 'Chest tightness.', 'A chronic cough that may produce mucus (sputum) that may be clear, white, yellow or greenish.', 'Frequent respiratory infections.', 'Lack of energy.', 'Unintended weight loss (in later stages)']