Forced Expiratory Volume in 6 s (FEV(6)) and FEV(1)/FEV(6) Values as a Viable Alternative for Forced Vital Capacity (FVC) and FEV(1)/FVC Values During Pregnancy in South East Nigeria: A Preliminary Study

BACKGROUND: Forced expiratory volume in 6 s (FEV(6)) and FEV(1)/FEV(6) ratio have traditionally been used as a surrogate for forced vital capacity (FVC) and FEV(1)/FVC in the assessment of spirometric lung function in nonpregnant subjects. However, the existence of this relationship during pregnancy is yet to be ascertained. AIM: The aim of this study was to determine if FEV(6) and FEV(1)/FEV(6) can effectively be used instead of FVC and FEV(1)/FVC in the interpretation of lung function test during pregnancy. SUBJECTS AND METHODS: This study was a descriptive cross-sectional study carried out among 200 pregnant women who were recruited by using systematic random sampling during the period between April and October 2011. One hundred matched nonpregnant women served as control. A standard spirometer was used to determine the FVC, FEV(6), FEV(1)/FVC, and FEV(1)/FEV(6). Data analysis was done using SPSS version 11.0 (Chicago, IL, USA). Values were recorded as mean (standard deviation), and also median and interquartile ranges. The one-way analysis of variance, Mann–Whitey U and the Kruskal–Wallis were used to test for significance where applicable. P <0.05 were considered to be significant. RESULTS: All the values were within normal range, but the FVC and FEV(6) decreased significantly while the FEV(1)/FVC and FEV(1)/FEV(6) increased as pregnancy progressed. However, for first and last trimester, FVC differed significantly from FEV(6). The values of the FVC were comparable to the values of FEV(6). The FEV(1)/FVC and FEV(1)/FEV(6) ratio were similar and well above the 0.7 cutoff for obstructive lung diseases. CONCLUSION: FEV(6) requires a short exhalation time and can effectively be used in place of FVC in evaluation of lung function test during pregnancy. The FEV(1)/FEV(6) may be applied as a proxy for FEV(1)/FVC in pregnant and nonpregnant women.