Value of forced expiratory volume in 6 seconds (FEV(6)) in the evaluation of pulmonary function in Chinese elderly males

Abstract

Objective: To evaluate the value of forced expiratory volume in 6 seconds (FEV(6)) in the evaluation of pulmonary function in Chinese elderly males. Methods: Pulmonary function tests of elderly who had received regular physical examination in Beijing Hospital from July 2003 to April 2015 were analyzed on subjects with the following characteristics: aged 60 years or older, completion of bronchial dilation test and able to exhale for at least six seconds. The included subjects were divided into 2 groups: 60-<80 years group and ≥80 years group. The association of FEV(6) with forced vital capacity (FVC), FEV(1)/FEV(6) with FEV(1)/FVC, the diagnostic efficiency and influencing factor of FEV(6) and FEV(1)/FEV(6) were analyzed; the value of FEV(6) in the evaluation of pulmonary function in the study population was evaluated. Results: A total of 475 elderly men aged 60 years or older were enrolled, with a mean age of (77.13±9.53) years. Totally there were 269 subjects in 60-<80 years group, which accounted for 56.6%; 206 subjects were in ≥80 years group, which accounted for 43.4%. There were 292 subjects with irreversible airflow obstruction, accounting for 61.5%. In all the included subjects, FEV(6) was significantly correlated with FVC and post-bronchodilator FEV(1)/FEV(6) was significantly correlated with post-bronchodilator FEV(1)/FVC(r=0.971, 0.978; both P<0.001), which were similar in 60-<80 years group and ≥80 years group (r=0.967, 0.974 and r=0.955, 0.967; all P<0.001). FEV(1)/FEV(6) showed excellent accuracy in diagnosing airflow obstruction[area under curve (AUC)=0.990(95%CI: 0.983-0.996); P<0.001]. Using FEV(1)/FVC<0.70 as a reference, FEV(1)/FEV(6)<0.73 had the best sensitivity (0.952) and specificity (0.945), and there was excellent agreement between the two diagnostic cutoffs (κ=0.891; P<0.001). When difference between before and after bronchial dilation test was analyzed, no correlation was observed between FEV(6) improvement and the improvement of forced expiratory time (r=0.089; P=0.053), but FVC improvement was significantly correlated with the improvement of forced expiratory time (r=0.460; P<0.001). Similar results were also found in subjects with irreversible airflow obstruction. Subjects with FEV(1)/FEV(6)≥0.70 and FEV(1)/FVC<0.70 were categorized as pulmonary function middle group, a total of 73 cases, which included 20 cases ≥80 years old. The proportion of middle group among ≥80 years group was significantly less than that of the 60-<80 years group (χ(2)=8.958; P=0.003). In pulmonary function middle group, FEV(1)/FEV(6) or FEV(1)/FVC had no correlation with inspiratory capacity or residual volume/total lung capacity (all P>0.05). Conclusions: FEV(6) and FEV(1)/FEV(6) are strongly correlated with FVC and FEV(1)/FVC, and there is excellent agreement between FEV(1)/FEV(6) and FEV(1)/FVC. FEV(6) is simple, easy to operate and with less influencing factors, which can be used as a valid alternative for FVC in diagnosing airflow obstruction in elderly males.