Measurement of inspiratory flow in children with acute asthma

Dry-powder inhalers (DPIs) have been proposed for treatment of acute asthma. Different DPIs vary in their inspiratory resistance and have different recommended optimal peak inspiratory flows (PIFs). Reduced PIF during acute asthma may result in inadequate drug delivery to the lungs. Our aim was to measure the inspiratory flow in relation to inspiratory resistance during acute asthma in children presenting to the emergency room. School-age (range, 6-18 years) children were referred to the emergency room for acute asthma. PIF measurements were performed by In-Check Dial™ device with simulated airflow resistances equivalent to Turbuhaler®, Diskus®, and free flow. Percent change in PIF between remission and acute asthma (%Δ) was correlated with percent change in clinical score (CS) and percent change in spirometry in children <9 and >9 years old. Thirty-three children (21 males) participated. PIF with simulated Turbuhaler resistance was significantly lower than with simulated Diskus resistance in both acute and remission states (P < 0.0001). PIF with simulated Turbuhaler resistance increased from 62.1 ± 15.3 (acute) to 74.4 ± 16.5 l/min (remission, P < 0.0001), while with Diskus it rose from 72.6 ± 20.5 to 91.1 ± 18.9 l/min (P < 0.0001). Turbuhaler %Δ PIF correlated with %Δ FEV₁, (P = 0.01) and with %Δ CS (P = 0.0001). A lesser degree of correlation was observed while using Diskus resistance and in children above 9 years old. During acute asthmatic attacks, PIF is reduced; this reduction is particularly prominent in young children who use a high-resistance device. However, the PIF generated is generally within the values considered compatible with adequate lung deposition with both Diskus and Turbuhaler.