Mite avoidance can reduce air trapping and airway inflammation in allergic asthmatic children

We investigated the effects of prolonged allergen avoidance in 18 house dust mite-sensitized asthmatic children during a prolonged residential period at a high altitude, allergen-free environment. METHODS: Evaluations of residual volume (RV) and exhaled nitric oxide (eNO) were performed (i) at admission to the residential house in September, (ii) in December after 3 months of stay, (iii) in January after 15 days at home, exposed to allergens, and (iv) in June after 9 months of stay. RESULTS: During the study period RV showed a significant decrease in December (from 117.5 +/- 7.7\% to 96.5 +/- 3.2\%) (P < 0.02) and a following increase in January (126.2 +/- 17.2\%), after allergen re-exposure (P < 0.03). RV decreased again in June at the end of the study period (91.1 +/- 6.0\%) (P = 0.001). FEV(1), FEF(25-75) and VC values did not present significant variations. ENO showed a significant decrease in December after 3 months at high altitude (from 21.3 +/- 3.9 p.p.b. to 11.9 +/- 1.7 p.p.b.) (P = 0.03), but no further significant change. No correlation was found between lung volumes and eNO, probably reflecting different aspects of asthma. CONCLUSIONS: Results suggest that RV may be more sensitive than other respiratory function parameters in identifying children with air trapping, being influenced significantly as the inflammatory indices by effective allergen avoidance/exposure regimen.