Study objective: The purpose of the study was to compare peak expiratory flow rate (PEFR) against 1-second forced expiratory volume (FEV1) 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 FEV1 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 FEV1 and PEFR were obtained from 199 patients and compared. There was good correlation between PEFR and FEV1, both in terms of absolute value (r=84; P<.001) and in terms of PPV (r=81; P<.001). Despite good correlation, further analysis revealed that there was not uniformly good agreement between the PPVs for FEV1 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 FEV1 is not available, there may be clinically significant discrepancies between the two tests. Measurement of the FEV1 is preferable because it allows comparison with baseline studies and previously published guidelines.