Forced expiratory volume in the third second and its derivatives for diagnosis of airway obstruction in obese patients

Abstract

BackgroundSpirometry is a simple diagnostic tool for pulmonary diseases, as obstructive pulmonary disorders, especially in obese. Obesity is an increasing worldwide public health concern that contributes to many respiratory problems that affect both large and small airways. The traditional use of forced expiratory volume in the first second (FEV1) and FEV1/forced vital capacity (FVC) in defining large-airflow obstruction may be confined not only by the limitation of FVC maneuver, but also by the long time to reach plateau flow rate in geriatrics and in patients with moderate-to-severe airflow obstruction. FEV3 and its derivatives FEV1/FEV3 and FEV3/FVC are used for better diagnosis of obstruction, especially in deteriorated patients who cannot blow for more than or equal to 6 s even after their best trials. Regarding small-airway obstruction, FEV3/FEV6 abnormality may be used to diagnose it in the early stages, especially with obesity.AimTo compare the accuracy of FEV3, FEV1/FEV3, and FEV3/FEV6 with that of FVC, FEV1/FVC, and forced expiratory flow (FEF) 25–75% as indices for large-airway and small-airway obstruction in obese persons, in order to replace the ordinary spirometric maneuvers that are easier to perform.Patients and methodsIn this study, 95 patients were enrolled. All participants were classified according to BMI into normal, overweight, and obese groups. FEV1, FEV3, FEV6, FVC, FEV1/FVC%, FEV1/FEV3%, FEV3/FVC%, and FEV3/FEV6% were determined.ResultsFifty participants were males, 52.63%, and 45 were females, 47.37%. Acceptable accuracy of FEV1/FEV3 test for diagnosis of large-airway obstruction, if compared with FEV1/FVC. While FEV3/FVC test showed less-satisfied accuracy. FEV3/FEV6 failed to show an acceptable accuracy for diagnosis of small-airway obstruction when compared with FEF25–75%. Regarding the effect of BMI on spirometric values, FEV1/FVC (P = 0.027), FEV1/FEV3 (P = 0.029), and FEF25–75% (P = 0.002) were more significant in obese patients than overweight patients or normal participants. No differences in FEV3/FVC and FEV3/FEV6 were found among the various groups studied.ConclusionTargeting obese persons, FEV3 and its derivatives as FEV1/FEV3 and to a lesser extent FEV3/FVC can be used as substitutes for FVC and FEV1/FVC, respectively, for evaluation of large-airway obstruction, while FEV3/FEV6 cannot identify people with small-airflow obstruction.