FEV ₆ as an alternative for FVC in detecting airflow obstruction in COPD patients undergoing six minute Walk test

Forced expiratory volume in 6 seconds (FEV 6 ) could complement forced expiratory volume in 1 second (FEV 1 ) and forced vital capacity (FVC) for detecting airflow obstruction in chronic obstructive pulmonary disease (COPD). Our aim is to evaluate the use of the FEV 1 / FEV 6 and FEV 6 as an alternative for FEV 1 /FVC and FVC in the detection of dynamic hyperinflation during six minute walk test (6MWT). Sixty-two ambulatory and clinically-stable COPD patients were randomized to this cross-over study. One group of 31 patients performed the spirometry by FVC first, then measuring FEV 6 , before and after 6MWT. The other 31 patients initiated the maneuver of FEV 6 first, then followed by FVC, during the 6MWT. FVC, FEV 1 , inspiratory capacity (IC), FEV 6 and FEV 1 /FEV 6 were recorded. FEV 6 and FEV 1 /FEV 6 were strongly correlated with FVC (r=0.907, n=62, p<0.0001) and FEV 1 /FVC (r=0.865, n=62, p<0.0001) before 6MWT. Values of FEV 6 and FEV 1 /FEV 6 were also strongly related to FVC (r=1.00, n=62, p<0.0001) and FEV 1 /FVC (r=0.809, n=62, p<0.0001) after 6MWT. We found that FVC showed good correlation to pre-exercise IC (r=0.697, n=62, p<0.0001) and post-exercise IC (r=0.642, n=62, p<0.0001). The value of FEV 6 also have similar correlation with pre-exercise IC (r=0.593, n=62, p<0.0001) and post-exercise IC (r=0.584, n=62, p<0.0001). The delta IC was correlated with delta FEV 6 (r=-0.357, n=62, p=0.004), however, was not related to delta FVC (r=-0.093,n=62, p=0.470).In conclusion, FEV 6 and FEV 1 /FEV 6 can be used as a valid alternative for FVC and FEV 1 /FVC to detect airway limitation or dynamic hyperinflation during 6MWT.