Effect of inhaled dust mite allergen on regional particle deposition and mucociliary clearance in allergic asthmatics

Background Acute exacerbations in allergic asthmatics may lead to impaired ability to clear mucus from the airways, a key factor in asthma morbidity. Objective The purpose of this study was to determine the effect of inhaled house dust mite challenge on the regional deposition of inhaled particles and mucociliary clearance (MCC) in allergic asthmatics. Methods We used gamma scintigraphy (inhalation of (99m)Tc -sulphur colloid particles) to measure the regional particle deposition and MCC in allergic asthmatics (n = 12) 4 h following an inhaled dust mite allergen challenge (Dermatophagoides farinae extract; PD(max) = fall in forced expiratory volume in 1 s of 10%) for comparison with baseline non-challenge measures. Results In responders (n= 9 PD(max) dose), lung function returned to pre-challenge values by 3 h but was significantly decreased at 6 and 24 h in three of the responders (i. e. late-phase response) and induced sputum eosinophils were increased at 24 h post-challenge (P<0.05). Responders showed enhanced bronchial airway deposition of inhaled particles (P<0.05) and slowed clearance from the central lung zone (P<0.01) at 4 h post-challenge compared with the baseline (no allergen challenge) that was predicted by the PDmax allergen concentration (r = -0.70, P<0.05). The decline in lung function at 24 h post-challenge correlated with reduced MCC from the central lung zone (r = -0.78, P<0.02) and PDmax. Non-responders (n = 3) showed no change in lung function, regional deposition or MCC post-challenge vs. baseline. Conclusions and Clinical Relevance These data suggest that regional deposition and clearance of inhaled particles may be sensitive for detecting mild airway obstruction associated with early-and late-phase allergen-induced effects on mucus secretions. The study was listed on clinicaltrials. gov (NCT00448851).