The Science Journal of the American Association for Respiratory Care

1996 OPEN FORUM Abstracts

Definition of Epidemiology, Pathophysiology and Diagnosis of COPD

James K. Stoller, M.D., Head, Section of Respiratory Therapy, Department of Pulmonary and Critical Care Medicine, Cleveland Clinic Foundation Sunday, November 3, 1996

As part of the recent ATS Standards for the Diagnosis and Care of Patients with Chronic Obstructive Pulmonary Disease, a discussion on definitions, epidemiology, pathophysiology, diagnosis and staging was included. This presentation will summarize these topics.

Chronic obstructive pulmonary disease continues to pose a major health burden in the United States today. Specifically, estimates suggest 14 million persons with chronic obstructive pulmonary disease in the United States and 85,000 annual deaths (death rate of 18.6/100,000 persons), rendering this the fourth leading cause of death in the United States today.

The diagnostic spectrum of chronic obstructive pulmonary disease includes chronic bronchitis, asthma, and emphysema, with significant overlap among these different entities.

Among the available etiologies of chronic obstructive pulmonary disease, cigarette smoking poses the major hazard. Another significant etiology is alpha-1 antitrypin deficiency, both because it is a familial disease as well as because of specific diagnostic and treatment implications related to alpha-1 antitrypsin deficiency.

The pathologic spectrum of chronic obstructive pulmonary disease includes centriacinar emphysema, panacinar emphysema, and paraseptal emphysema, concepts which will be reviewed in this talk. Laboratory testing is invaluable in the diagnosis and management of chronic obstructive pulmonary disease. Most importantly, spirometry before and after an inhaled bronchodilator is essential. Measurements of diffusing capacity and arterial blood gases may often be helpful.

Although high resolution CT scans are proven to be very sensitive in the diagnosis of chronic obstructive pulmonary disease, the ATS document does not support routine use of CT in clinical management of the patient with chronic obstructive pulmonary disease.

With regard to prognosis, measurement of FEV_{1} has proven to be a potent predictor of prognosis, with mortality rates associated with FEV_{1} values falling below 1 liter. The presence of hypoxemia worsens survival, but supplemental oxygen for patients with significant hypoxemia has been shown to prolong survival.

Finally, the ATS document proposes a new clinical staging system as follows: Stage I includes patients whose FEV_{1} is >= 60% predicted. Stage II includes patients whose FEV_{1} is between 35-49% predicted, and Stage III includes patients whose FEV_{1} is below 35% of predicted.

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