Montelukast improves pulmonary function measured by impulse oscillometry in children with asthma (Mio study).

Background: Systemic drugs-like oral montelukast can reach lower airways, whose inflammation plays a crucial role in the evolution of asthma, while inhaled drugs hardly reach them. The impulse oscillometry (IOS) technique is useful to evaluate both central and peripheral airways function.

Objective: To measure the effect of oral montelukast on airways resistance evaluated by oscillometry in children with asthma.

Methods: In an open study, respiratory function in 23 children with mild asthma and a positive bronchodilator response was assessed by spirometry and oscillometry. They took oral montelukast during 4 weeks and were again evaluated. As a control group, 23 similar patients with no preventive treatment underwent the same study.

Measurements And Main Results: Children on oral montelukast showed improvements (measured in kPa s L(-1)) in all oscillometry parameters: mean 0.20 (22.4%) in total respiratory impedance Zrs5, 0.18 (21.8%) in total airway resistance Rrs5, 0.09 (17.8%) in central airway resistance Rrs20, and 0.09 (28.8%) in distal capacitive reactance Xrs5; the frequency of resonance Fres improved 2.3 Hz (8.7%) (P<0.05 in all cases). No changes were found in the control group. Expiratory flows showed no changes except for a small (0.23 L s(-1), 7.4%) but significant worsening of FEF25-75 in the control group.

Conclusions: Montelukast improves central and especially peripheral airways function in the first month of treatment, as evaluated by IOS, a technique based on tidal breathing analysis which is more sensitive than conventional forced spirometry.