Question: The diagnosis coding for chronic obstructive pulmonary disease (COPD) confuses me. What separates the different COPD ICD-9 codes? North Carolina Subscriber Answer: The correct code will depend on whether the patient had a specified exacerbation along with the COPD. Report 491.21 (Obstructive chronic bronchitis; with [acute] exacerbation) for patients diagnosed with COPD who have had an exacerbation. Report 491.20 (Obstructive chronic bronchitis; without exacerbation) for patients diagnosed with COPD classified as obstructive "bronchitis" by the physician in the documentation/medical record, but without an exacerbation. When the physician does not fully classify the COPD, report 496 (Chronic airway obstruction, not elsewhere classified).