Beyond its impact on mortality, COPD leads to considerable morbidity. Acute exacerbations of COPD (AECOPDs) contribute to the disproportionate health burden of COPD. AECOPDs present a short-term risk for death and result in an accelerated decline in lung function. Patients often do not suffer a single exacerbation but tend to experience multiple exacerbations over their lifetimes. Furthermore, AECOPDs are a common reason for nonsurgical hospitalization and account for approximately one-half of the direct medical costs related to COPD.

AECOPDs can range in severity from mild to life threatening. Physicians can treat some individuals safely as outpatients. Other subjects may require mechanical ventilation (MV) for respiratory failure. In addition, some with AECOPD may initially respond to therapy but then decline. Unfortunately, clinicians lack a simple, validated risk-stratification tool for assessing the likely prognosis and severity of AECOPDs. For other diseases that share these features of variability in disease severity and the potential for a rapid change in patient status, clinicians can use various risk-stratification schemes. For example, both the Pneumonia Severity Index and the CURB-65 (confusion, urea, respiratory rate, BP) score serve as easy-to-apply and reliable severity-of-illness scoring rubrics in community-acquired pneumonia. The Pulmonary Embolism Severity Index and the Prognosis in Pulmonary

Embolism scores exist to aid in the management of acute pulmonary embolism. Unfortunately, although risk-assessment tools exist for patients with stable COPD, none have been validated for use in AECOPD.

A disease-specific severity-of-illness score for AECOPD would serve to improve treatment. It would facilitate triage decisions and identify patients who might potentially benefit for early and aggressive use of selected interventions, such as noninvasive ventilation. A reliable severity-of-illness score could also be applied in clinical trials. It would provide a standardized means for describing the patients studied while helping to ensure that the populations in these trials were well balanced with respect to disease severity.