Back pain is not directly a symptom of chronic obstructive pulmonary disease (COPD). If breathing is labored, however, that can cause strain of the ribs and other chest wall structures, such as muscles, ligaments, etc. Another possibility would be rupture of a bleb, a bubble on the lung, resulting in a pneumothorax. Given that you should probably see your doctor for an examination and chest x-ray.
Good luck.
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