Lung clearance index: A sensitive measure of airway function improvement in adolescents after weight loss from bariatric surgery

Background: Morbid obesity in adolescents impacts respiratory function, often leading to reduced lung volume and obstructive ventilatory defects. However, standard spirometric values frequently remain within normal ranges. Objectives: We hypothesized that Lung Clearance Index (LCI) is a more sensitive marker for detecting airway dysfunction in adolescents with morbid obesity than conventional lung function tests. Methods: A prospective single-center cohort study evaluated adolescents with morbid obesity undergoing laparoscopic sleeve gastrectomy (LSG). Assessments included fractional exhaled nitric oxide, multiple breath washout, spirometry, plethysmography, diffusion capacity, and a 6-min walk test, conducted pre- and post-surgery. Results: Seventeen adolescents (mean age 17.1 years, BMI 45.5 kg/m²) were studied. Pre-surgery, LCI was slightly elevated (mean 7, SD ± 0.7), other lung function measures were normal. LCI correlated with BMI (r = 0.637, p = 0.014), no correlation was found between FEV₁ and BMI (r = −0.083, p = 0.752). Post-surgery, mean LCI fell from 7 (±0.7) to 6.5 (±0.7), p = 0.009. The pre-operatively observed correlation between LCI and BMI was no longer present post-operatively (r = 0.362, p = 0.225). LCI changes (r = 0.676, p = 0.011) correlated with BMI changes, whilst FEV₁ did not (r = 0.160, p = 0.540). Conclusions: LCI appeared to be a more sensitive marker than conventional spirometry for detecting airway dysfunction in adolescents with morbid obesity. Significant post-surgery improvements suggested enhanced ventilation homogeneity. LCI may detect subtle airway changes in this population, and be potentially valuable for both clinical assessment and research.