Data collection from medical charts was conducted at Far Eastern Memorial Hospital, a tertiary-care hospital with around 900 beds. Patients who were admitted from January 2008 to December 2008 and diagnosed as having chronic obstructive pulmonary disease with acute exacerbation (code ICD-9: 491.21) were included in this study. The study was approved by the Institutional Review Board of the Far Eastern Memorial Hospital (FEMH:098097-3).