Redefining Spirometry Hesitating Start Criteria Based on the Ratio of Extrapolated Volume to Timed FEVs

A new hesitating start criterion using EV/FEV6 of 5.25% is recommended for tracings that do not achieve a plateau or when an FEV6 is performed. An EV/FEV3 of 5.59% could be incorporated into spirometry software as an early warning signal that could help operators identify trials with potential hesitating starts.