D2.167 - Impact of body mass index on oscillometry parameters in children with respiratory symptoms

Childhood obesity is a growing public health concern and has been associated with potential impact on central and peripheral airways. Impulse oscillometry (IOS) offers a sensitive effort-independent assessment of small airway function that may not be evident on conventional spirometry. Evidence on the relationship between body mass index (BMI) and IOS parameters in children with respiratory symptoms remains limited.

We aimed to evaluate associations between BMI and IOS parameters in children and adolescents undergoing pulmonary function testing.

Retrospective analysis of IOS performed between 2023-2024 in pediatric patients in our Pulmonary Function Laboratory. Patients were classified according to World Health Organization BMI-for-age reference curves into normal weight, overweight and obesity groups. Demographic, clinical, spirometric and oscillometric data were collected.

This study included 262 patients (mean age 10±3.6 years), 54.2% male. Based on BMI, 61.1% had normal weight, 22.5% overweight and 16.4% obesity. Primary diagnosis included asthma (64.9%), rhinitis (19.1%), recurrent wheezing (10.3%) and exercise-induced bronchospasm (5.7%). Atopy was present in 79%.

Among children with asthma, the normal weight group (NWG) and overweight group (OWG) had significantly higher FEV1/FVC ratios compared to the obesity group (OG) (p=0.002 and p=0.012, respectively). No other significant differences were observed.

IOS revealed significantly higher resistance at 5Hz (R5%) predicted in the NWG compared to the OWG (p=0.013).

Resistance at 20Hz (R20) was significantly higher in OG compared to OWG (p=0.027). Area of reactance (AX) was significantly increased in OG compared to NWG (p=0.033). Although reactance at 5Hz (X5) tended to be more negative and resonant frequency (FRES) higher in children with higher BMI, these did not reach statistical significance. No significant associations were found between BMI and fractional exhaled nitric oxide, bronchodilator response or peripheral blood eosinophils.

In children with asthma, obesity was linked to reduced FEV₁/FVC ratio and central and peripheral airway changes detected by IOS, particularly elevated R20 and AX, respectively. These findings suggest obesity may impact airways mechanics independently of inflammatory pathways, as evidenced by the lack of association with inflammatory markers. Our study supports the use of IOS as complementary tool to evaluate obesity-related respiratory functional patterns in pediatric patients.