Hevroni A, et al. - In this retrospective analysis of 156 infants aged 3–24 months with persistent or recurrent respiratory complaints, researchers assessed tidal breathing (TB) flow-volume and flow-time curves for detection of expiratory airway obstruction. They compared parameters derived from TB curves (including inspiratory time (t_I), expiratory time (t_E), tidal volume, peak tidal expiratory flow (PTEF), time to peak tidal expiratory flow (t_PTEF), expiratory flow when 50% and 25% of tidal volume remains in the lungs (FEF₅₀, FEF₂₅, respectively), and the ratios t_PTEF/t_E, t_I/t_E, FEF₅₀/PTEF, and FEF₂₅/PTEF) vs maximal expiratory flow at functional residual capacity (V˙maxFRC) assessed by rapid thoracoabdominal compression technique. t_PTEF/t_E, FEF₅₀/PTEF, and FEF₂₅/PTEF displayed the best correlations to V˙maxFRC. Areas under the curve of 0.813, 0.797, and 0.796 were demonstrated by ROC curves for FEF₅₀/PTEF, FEF₂₅/PTEF and t_PTEF/t_E, respectively. For these three parameters, the respective cutoff value z-scores of −0.35, −0.34, and −0.43 displayed an 86% negative predictive value for severe airway obstructions. Overall, TB curves could be of help in ruling out severe expiratory airway obstruction in infants.