Fixed Airflow Obstruction in Asthma Can Be Identified Early by Low FEF25-75% and is Associated with Environmental Exposure

Ziheng Chen,1 Jinxin Ma,1 Jiahui Lei,1 Yi Li,1 Ruijuan Zhao,1 Limin Zhao2 1Department of Respiratory and Critical Care Medicine, Zhengzhou University People’s Hospital, Henan Provincial People’s Hospital, Zhengzhou, Henan, People’s Republic of China; 2Department of Respiratory and Critical Care Medicine, Henan Provincial People’s Hospital, Zhengzhou University People’s Hospital, Henan University People’s Hospital, Zhengzhou, Henan, People’s Republic of ChinaCorrespondence: Limin Zhao, Department of Respiratory and Critical Care Medicine, Henan Provincial People’s Hospital, Zhengzhou University People’s Hospital, Henan University People’s Hospital, 7 Weiwu Road, Jinshui District, Zhengzhou, Henan, 450003, People’s Republic of China, Email [email protected]: This study aimed to identify environmental risk factors associated with asthmatic fixed airflow obstruction (FAO) and assess the relationship between small airway abnormalities defined by forced expiratory flow at 25– 75% (FEF25-75%) and FAO.Patients and Methods: We analyzed data from 312 han Chinese patients with stable asthma on standard treatment. Low FEF25-75% was defined as post-bronchodilator FEF25-75% z-score 10 years (2.01 [1.06– 3.86], P=0.035) and occupational exposure for > 20 years (2.67 [1.24– 5.91], P=0.013) were associated with asthmatic FAO. In cross-sectional analyses, compared with the normal FEF25-75%/ asthmatics without FAO (NON-FAO) group, the low FEF25-75%/ asthmatics with FAO (FAO) group had lower FEV1 z-scores and FEV1/FVC z-scores, more pack-years and years of biomass and occupational exposure, higher Asthma Control Questionnaire-5 and Chronic Obstructive Pulmonary Disease Assessment Test scores, and more frequent exacerbations. The low FEF25-75%/NON-FAO group showed the same trend, but to a lesser extent.Conclusion: Chronic airway inflammation is not the only driver of asthmatic FAO, and management and treatment targeting environmental risk factors (smoking and biomass and occupational exposures) may slow FAO progression in asthmatics. The FEF25-75% determined by the z-score is a reliable marker of small airway abnormalities, and patients with low FEF25-75% are at greater risk for FAO, requiring more frequent follow-up.Keywords: asthma, fixed airflow obstruction, environmental exposures, forced expiratory flow at 25-75%