Application of MEFV Curve in the Intrathoracic Large Airway Obstruction: a retrospective study

Background Maximum expiratory flow-volume (MEFV) curve played an important part in diagnosing the intrathoracic large airway obstruction (ILAO). This study aimed to explore potential discriminative indicators for ILAO by MEFV curve. Methods In this retrospective observational study, we collected pulmonary function tests of patients with ILAO or chronic obstructive pulmonary disease (COPD). They were randomly classified into model and validation groups. The predictive model for ILAO was established by forced expiratory flow (FEF) _50% /FEF _25% and Empey’s index, and subsequently validated. Results Between January, 2012, and December, 2021, 63 patients with ILAO and 64 with COPD were included. The peak expiratory flow (PEF), FEF _50% , FEF _75% , FEF _{25 − 75%} , FEF ratios and Empey’s index were significantly different in two group. In the model group, the receiver operating characteristic (ROC) curve results showed that the areas under the curve (AUCs) were as follows: FEF _50% /FEF _25% 0.935(P = 0.000), FEF _75% /FEF _50% 0.623 (P = 0.091), FEF _75% /FEF _25% 0.795 (P < 0.001) and Empey’s index 0.922 (P < 0.001). When FEF _50% /FEF _25% was ≥ 0.960, sensitivity and specificity were 93.8% and 87.5%. When Empey’s index was ≥ 7.415, sensitivity and specificity were 84.4% and 100%. When FEF _50% /FEF _25% ≥0.960 and Empey’s index was ≥ 7.415, sensitivity and specificity were 81.3% and 87.5%. The predictive performance of FEF _50% /FEF _25%, Empey’s index and the combined parameters were calculated in the validation group, with high sensitivity and acceptable specificity. Conclusions The predictive model for ILAO established using FEF _50% /FEF _25% and Empey’s index demonstrates good practical value, which makes FEF _50% /FEF _25% and Empey’s index potential discriminative indicators for ILAO.