The purpose of this study is to determine whether there is a statistical association between changes in sputum serial levels of two cytokines, interleukin (IL)-17 and IL-6, during the treatment course of a severe acute exacerbation of chronic obstructive pulmonary disease (AE-COPD) and during the clinical course itself (i.e., rate of recovery or potential complicated course). AE-COPD is defined as an episode requiring emergency room (ER) evaluation.