Pulmonary function of children with tracheomalacia and associated clinical factors

Objectives: Spirometry is easily accessible yet there is limited data in children with tracheomalacia. Availability of such data may inform clinical practice. We aimed to describe spirometry indices of children with tracheomalacia, including Empey index and flow-volume curve pattern, and determine whether these indices relate with bronchoscopic features. Methods: From the database of children with tracheomalacia diagnosed during 2016–2019, we reviewed their flexible bronchoscopy and spirometry data in a blinded manner. We specially evaluated several spirometry indices and tracheomalacia features (cross-sectional lumen reduction, malacic length, and presence of bronchomalacia) and determined their association using multivariable regression. Results: Of 53 children with tracheomalacia, the mean (SD) peak expiratory flow (PEF) was below the normal range [68.9 percent of predicted value (23.08)]. However, all other spirometry parameters were within normal range [Z-score forced expired volume in 1 s (FEV₁) = −1.18 (1.39), forced vital capacity (FVC) = −0.61 (1.46), forced expiratory flow between 25% and 75% of vital capacity​​​​​​ (FEF_25%–75%) = −1.43 (1.10), FEV₁/FVC = −1.04 (1.08)], Empey Index = 8.21 (1.59). The most common flow-volume curve pattern was the “knee” pattern (n = 39, 73.6%). Multivariable linear regression identified the presence of bronchomalacia was significantly associated with lower flows: FEV₁ [coefficient (95% CI) −0.78 (−1.54, −0.02)], FEF_25%–75% [−0.61 (−1.22, 0)], and PEF [−12.69 (−21.13, −4.25)], all p ≤ 0.05. Other bronchoscopic-defined tracheomalacia features examined (cross-sectional lumen reduction, malacic length) were not significantly associated with spirometry indices. Conclusion: The “knee” pattern in spirometry flow-volume curve is common in children with tracheomalacia but other indices, including Empey index, cannot be used to characterize tracheomalacia. Spirometry indices were not significantly associated with bronchoscopic tracheomalacia features but children with tracheobronchomalacia have significantly lower flow than those with tracheomalacia alone.