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.