Pulmonary function and physical fitness in obese children and adolescents: a comparison of impulse oscillometry, spirometry, and 6-min walk test

UNLABELLED: Obesity-associated alterations in pulmonary function have been inconsistently identified by spirometry in pediatric populations. Impulse oscillometry (IOS) offers sensitive detection of peripheral airway resistance, yet data remain limited. Moreover, the relationship between obesity indices and pulmonary function has not been comprehensively evaluated. This study aimed to compare pulmonary function and physical fitness between obese and normal-weight children and adolescents using spirometry, IOS, and the 6-min walk test (6-MWT), and assessed obesity indices as predictors of pulmonary outcomes. We enrolled 120 participants aged 8 to 15 years (obese: n = 82; normal weight: n = 38). Anthropometry included body mass index (BMI), waist circumference-to-height ratio (WHR), and chest circumference-to-height ratio (CCHR). Pulmonary function was assessed by IOS and spirometry, and physical fitness by the 6-MWT. Obese participants exhibited higher forced vital capacity (FVC) percent predicted (114 ± 17 vs 106 ± 12; P = 0.02) and FVC z-score (1.09 ± 1.35 vs 0.52 ± 1.00; P = 0.02). The ratio of volume expired in 1 s to FVC was reduced (85.0 ± 5.3 vs 88.1 ± 5.8; P = 0.005), with no significant change in volume expired in 1 s. The 6-MWT distances were shorter in the obese group (542 ± 45 m vs 583 ± 59 m; P < 0.001), and z-score-adjusted distances were lower (0.29 ± 0.75 vs 1.24 ± 0.75; P < 0.001). Height- and sex-adjusted IOS parameters (R 5, R 20, R 5-20, Fres, AX) were elevated in obesity. Regression analysis identified BMI, WHR, and CCHR as independent predictors of reduced 6-MWT distance and increased R 5-20.

CONCLUSION: Pediatric obesity is associated with increased total, central, and peripheral airway resistance, and impaired physical fitness. BMI, WHR, and CCHR predict exercise limitation, while WHR and CCHR predict peripheral airway resistance.

WHAT IS KNOWN: • Pediatric obesity is associated with reduced FRC, lower FEV1/FVC ratios, and impaired physical fitness measured by the 6-min walk test.

WHAT IS NEW: • Impulse oscillometry (IOS) reveals increased total and peripheral airway resistance in obese children and adolescents, not evident on spirometry. • Central adiposity markers, specifically waist circumference-to-height ratio (WHR) and chest circumference-to-height ratio (CCHR), are robust independent predictors of elevated airway resistance and functional limitations.