1) Primary: time to all-cause mortality or re-hospitalization during the 180 days post-randomization. 2) Secondary: respiratory death or respiratory re-hospitalization during the 180 days post-randomization; rate of death or readmission during the 30 days post-discharge; treatment failure (see definition below); change in health status, FEV1, and dyspnea during the 180 days post-randomization; length of hospital stay during the index hospitalization. 3) Other: assess tolerance of roflumilast vs. placebo in hospitalized AECOPD.