A single decline of FEV3/FVC in determine the application potential of early lung disease

Abstract

Objective To explore the application potential of forced expiratory volume in three second/forced vital capacity (FEV3/FVC) in early lung diseases, such as early airway obstruction and mild gas trap. Methods A total of 288 patients (excluding those with restrictive ventilation dysfunction) who underwent pulmonary function examination in the pulmonary function room of our hospital from January 2014 to October 2017 were collected. 288 patients were divided into three groups. Group A: FEV3/FVC and forced expiratory volume in one second/forced vital capacity (FEV1/FVC) were normal; Group B: FEV3/FVC decreased alone; Group C: FEV1/FVC decreased. The general data and pulmonary function indexes of the three groups were compared. Results Compared with group A, group B had lower FEV1 % and diffusion capacity for carbon monoxide of the lung (DLCO%), but higher total lung capacity (TLC%), residual volume (RV%) and RV/TLC. Compared with group B, group C had higher TLC %, RV%, RV/TLC%, while FEV1%, DLCO% reduce more remarkably. There were significant differences in the three groups of small airway function (P<0.01). FEV3/FVC was positively correlated with max expiratory at 50% FVC (MEF50%), max expiratory at 75% FVC (MEF25%) and maximal mid expiratory flow (MMEF%). The correlation coefficients were respectively 0.613, 0.610, 0.608 (P<0.01). When FEV3/FVC serves as an indicator to determine airway obstruction, the specificity of it is 45.7%, sensitivity 98.5%, and negative predictive value 99%, positive predictive value 35.5%. Conclusions FEV3/FVC individual decline is the indication of early lung diseases such as mild airway obstruction , mild gas trap and diffuse disorder. Key words: Forced expiratory volume; Vital capacity; Respiratory function tests; Lung diseases