Abstract
Age appropriateness is a major concern of pulmonary delivery devices, in particular of dry powder inhalers (DPIs), since their performance strongly depends on the inspiratory flow manoeuvre of the patient. Previous research on the use of DPIs by children focused mostly on specific DPIs or single inspiratory parameters. In this study, we investigated the requirements for a paediatric DPI more broadly using an instrumented test inhaler. Our primary aim was to assess the impact of airflow resistance on children’s inspiratory flow profiles. Additionally, we investigated children’s preferences for airflow resistance and mouthpiece design and how these relate to what may be most suitable for them. We tested 98 children (aged 4.7–12.6 years), of whom 91 were able to perform one or more correct inhalations through the test inhaler. We recorded flow profiles at five airflow resistances ranging from 0.025 to 0.055 kPa0.5.min.L−1 and computed various inspiratory flow parameters from these recordings. A sinuscope was used to observe any obstructions in the oral cavity during inhalation. 256 flow profiles were included for analysis. We found that both airflow resistance and the children’s characteristics affect the inspiratory parameters. Our data suggest that a medium-high resistance is both suitable for and well appreciated by children aged 5–12 years. High incidences (up to 90%) of obstructions were found, which may restrict the use of DPIs by children. However, an oblong mouthpiece that was preferred the most appeared to positively affect the passageway through the oral cavity. To accommodate children from the age of 5 years onwards, a DPI should deliver a sufficiently high fine particle dose within an inhaled volume of 0.5 L and at a peak inspiratory flow rate of 25–40 L.min−1. We recommend taking these requirements into account for future paediatric inhaler development.
Highlights
Drug delivery to the lungs is complex and involves several process steps depending on the inhalation device used
The profiles of four children, who were all younger than 6 years of age, were immediately excluded because they exhaled through the test inhaler
We investigated the applicability of dry powder inhalation in school children by a general approach using an instrumented test inhaler
Summary
Drug delivery to the lungs is complex and involves several process steps depending on the inhalation device used. To achieve sufficient pulmonary deposition, the inhalation device has to be prepared and operated correctly. For dry powder inhalers (DPIs), the inhalation manoeuvre is of utmost importance, as it determines both the fine particle dose delivered and the site of deposition of the particles in the lungs [1]. For most marketed DPIs, the energy for releasing and dispersing the powder into an aerosol with a proper aerodynamic particle size distribution is derived from the inhaled air stream through the inhaler. To have sufficient energy available, the airflow rate has to exceed a certain threshold value, which is dependent on the inhaler design, and the inhaled volume has to be sufficiently large for transport of the aerosol into the target area [2]. A breath hold period after inhalation is desired to give particles sufficient time for sedimentation in the central and peripheral airways [1]
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