• Zachary Q Morris, Najia Huda, and Robert R Burke.
• Henry Ford Health System, Division of Pulmonary and Critical Care Medicine, Detroit, Michigan, USA. zmorris1@hfhs.org
• COPD. 2012 Feb 1; 9 (1): 22-8.

BackgroundOn spirometry the FEV(1)/FEV(6) ratio has been advocated as a surrogate for the FEV(1)/FVC. The significance of isolated reductions in either the FEV(1)/FEV(6) or FEV(1)/FVC is not known.MethodsFirst-time adult spirograms (n = 22,837), with concomitant lung volumes (n = 12,040), diffusion (n = 14,154), and inspiratory capacity (n = 12,480) were studied. Four groups were compared. 1) Only FEV(1)/FEV(6) reduced (n = 302). 2) Only FEV(1)/FVC reduced (n = 1158). 3) Both ratios reduced (n = 6593). 4) Both ratios normal (n = 14,784).ResultsIn patients with obstructed spirometry (either a reduced FEV(1)/FVC and/or FEV(1)/FEV(6)), 3.8% only had a reduced FEV(1)/FEV(6), while 14.4% only had a reduced FEV(1)/FVC. The mean FEV(1) was lower when both ratios were reduced. The group with only a reduced FEV(1)/FEV(6), compared to only the FEV(1)/FVC reduced, had a lower FEV(1), FVC, BMI, Expiratory Time, and IC (p values < 0.0001). DL(CO) was also lower (p = 0.005), and the FEV(1)/FVC and RV/TLC were higher (p values < 0.0001). When the patients with only a reduced FEV(1)/FEV(6) had a subsequent spirogram, 60% had a reduced FEV(1)/FVC when their mean expiratory times were 3.5 seconds longer. Ninety percent of this group had strong clinical evidence of airways obstruction.ConclusionsThe FEV(1)/FEV(6) is not as sensitive as the FEV(1)/FVC for diagnosing airways obstruction, but in the presence of a normal FEV(1)/FVC, subjects have greater physiologic abnormalities than when only the FEV(1)/FVC is reduced. The FEV(1)/FEV(6) ratio should not replace the FEV(1)/FVC as the standard for airways obstruction, but there is benefit including this measurement to identify individuals with greater air trapping and diffusion abnormalities.

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