Exercise-induced bronchospasm in asthmatic Children. FENO and Body Mass Index relationship

Abstract

Exercise-induced bronchoconstriction (EIB) is frequent in children with asthma.FENO reflects eosinophilic inflammation and has been associated with EIB. Obesity has also been associated with EIB.

Objectives: Evaluate the relationship between clinical and functional state and EIB in asthmatic children.

Methods: Prospective study. Asthmatic children sent to the Respiratory Laboratory of P. Cassará Foundation were included. Treadmill exercise tests were performed as well as BMI, ACT and FENO measurements.

Results: n 144. Mean age 12.3 yrs (SD± 2.8 yr), male 60% (n=88). 28 of 144 children (20%) had EIB (FEV1 fall>12%).

Basal spirometry shows no relantionship with EIB. FENO was higher in EIB group (55 ppb RIQ 37-106 vs non-EIB 28 ppb, RIQ 20-57 p<0,0016). FENO ROC curve to discriminate EIB had an AUC of 0.73 (95% CI:0,65-0,82). ROC cutoff point for FENO=30.75 ppb (sensitivity 96%, specificity 52% p<0,0001); FENO negative predictive value 98% (0,91-0,99) and positive predictive value 32% (0,22-0,44) p<0,0001. FENO correlates with maximal decrease in FEV1 (r 0,34 P< 0,0001) and FMMF (r 0,27 P <0,0009) after exersice.

Children in EIB group had higher BMI (22.96 RIQ 18.6-25.3 vs 20.66 RIQ 18.0- 23.0 in non EIB p<0,026). Overweigth/obesity (BMI Z-score) had similar distribution in both groups. Higher BMI Z-score correlated with lower basal FEV1/FVC (r-0,23 p 0,005) and FMMF/FVC (r -0,17 p 0,037 ) and with larger drop in FMMF after exercise (r 0,20 p 0,01).No association was found between FeNO and BMI.

Conclusion: FENO is a useful tool for EIB screening.BMI Z-score, even within normal range, is associated with lower values of basal spirometry. FENO and BMI correlate with post exercise spirometry declination.