The authors found strong evidence for a benefit of inhaled beta-agonists, anticholinergics, and corticosteroids in reducing symptoms, hospitalization, and death due to COPD. However, the studies of these drugs were mostly done in patients with an FEV1 less than 60% and might not apply to patients with less severe lung abnormality. Evidence for a benefit of oxygen therapy was found for patients with very low resting blood oxygen levels. Some weak evidence indicated that pulmonary rehabilitation may help patients with COPD symptoms and an FEV1 less than 50%.