If mild (defined as not requiring mechanical ventilation and having only one of the three cardinal symptoms of increased dyspnea, sputum purulence or sputum production), NO.
If moderate to severe (defined as requiring mechanical ventilation or having at least two of the three cardinal symptoms), YES.
Which antibiotic?
If no risk factors for complicated COPD (age < 65, < 3 exacerbations/year, no cardiac disease), treat with macrolide (azithromycin), cephalosporin, doxycycline or trimethrprim/sulfamethoxazole; if 1 or more risk factors and no risk factors for pseuduomonas, treat with fluoroquinolone (moxifloxacin, gemifloxacin, levofloxacin), amoxicillin/clavulanate or ceftriaxone; if 1 or more risk factors for complicated COPD and risk factors for pseudomonas, treat with levofloxacin, cefepime, ceftazidime or piperacillin-tazobactam.
Bottom line, most folks that show up in the ED with a COPD exacerbation should recieve an antibiotic. Which type depends on their risk for complications and pseudomonas.
Source
Bartless, J. MD. Sethi, S. MD. "Diagnosis and treatment of infection in acute exacerbations of chronic obstructive pulomonary disease." Up to Date. Oct 2008.