Use of Peak Expiratory Flow Rate in Emergency Department Evaluation of Acute Exacerbation of Chronic Obstructive Pulmonary Disease

Abstract

Study objective: The purpose of the study was to compare peak expiratory flow rate (PEFR) against 1-second forced expiratory volume (FEV 1) as a measure of airway obstruction in patients with acute exacerbation of chronic obstructive pulmonary disease (COPD). Methods: The participants were patients older than 50 years of age who presented with an acute exacerbation of COPD to the emergency department of a large, urban medical center. Pulmonary function was measured with a computerized Fleisch pneumotachygraphic spirometer before, during, and after treatment. PEFR and FEV 1 were compared both as absolute values and after conversion to percent of predicted normal values (PPVs). Results: Five hundred fifty-six paired sets of measurements of FEV 1 and PEFR were obtained from 199 patients and compared. There was good correlation between PEFR and FEV 1, both in terms of absolute value ( r=.84; P<.0001) and in terms of PPV ( r=.81; P<.0001). Despite good correlation, further analysis revealed that there was not uniformly good agreement between the PPVs for FEV 1 and PEFR. Although the mean difference between the PPVs obtained from the two measurements was only 4.3%, the 95% limits of agreement ranged widely, from -15% to 24%. Conclusion: Although PEFR can be used as an alternative measure of airway obstruction in instances in which FEV 1 is not available, there may be clinically significant discrepancies between the two tests. Measurement of the FEV 1 is preferable because it allows comparison with baseline studies and previously published guidelines. [Emerman CL, Cydulka RK: Use of peak expiratory flow rate in emergency department evaluation of acute exacerbation of chronic obstructive pulmonary disease. Ann Emerg Med February 1996;27:159-163.]