Reversibility is assessed by spirometry before and after administration of an inhaled bronchodilator, most often a short-acting b2-adrenergic agonist. Testing should be performed when the patient is clinically stable. Short-acting bronchodilators should be withheld for 6 h, long-acting dilators for 12 h, and theophylline for 24 h prior to testing. A significant response is an increase of at least 12% and 200 mL in either FEV1 or forced vital capacity (FVC). Postbronchodilator FEV1 is useful for prognostication. Although only one-third of COPD patients show a significant response to an inhaled bronchodilator in the pulmonary function laboratory on any one day, two-thirds will show a significant response when tested with different bronchodilators on several different occasions. The degree of bronchodilator response at any one testing session does not predict the degree of clinical benefit to the patient. Therefore, bronchodilators are given irrespective of the acute response obtained in the pulmonary function laboratory. The American Thoracic Society recommends staging COPD by FEV1. Stage I, mild disease, is defined as FEV1 ?50% predicted; stage II, moderate disease, 35 to 49% predicted; and stage III, severe disease, <35% predicted.


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