Pediatric inhalation therapy and the aerodynamic rationale for age-based aerosol sizes.

Abstract

Inhalation aerosols represent a cornerstone in treating pediatric respiratory conditions and may be administered as soon as following birth in preterm neonates or shortly after in babies. Yet, deposition efficiencies (DE) of inhaled aerosols in the lungs of infants and young children are underwhelming, with typical outcomes <30% of the administered dose, and not uncommonly <5% depending on age and disease [1]. Despite progress in improving delivery devices, current reviews still stress the same upsetting message [2,3]. The rule of thumb might easily read: the younger the patient the worse the targeting efficiency to the lungs. The selection of an appropriate inhaler holds important ramifications in the effective dose delivered to a young patient’s lungs [4]. For example, infants and young children are unable to coordinate the inhalation maneuver necessary with metered dose inhalers (MDI). Concurrently, dry powder inhalers (DPIs) are typically advocated in older children as these require patient compliance through vigorous suction to de-aggregate the drug powder. Together these limitations, including the limited ability of young patients to hold their breath to increase the action of gravitational settling, hinder pulmonary DE and device options. For the youngest that are nose breathers, the practice of adapting face masks and intranasal prongs represents only incremental improvements. The underlying picture remains fundamentally unchanged. Treatment options and inhalation guidelines are broadly derived from devices and protocols established for adults whereby dosage adaptations in children, if any, are based on extrapolations often according to bodyweight [5]. Clinicians may prescribe inhaled medications that are disease appropriate but not necessarily approved for these young ages as the majority of inhalers and drug formulations are based on adult studies, or at the very least in older children [6]. This reality underscores a lack in considering more significantly the physical determinants of inhaled aerosol transport that influence pulmonary deposition. In improving pediatric inhalation therapy, we advocate below the mechanistic argument to adapt pharmaceutical aerosol sizes according to age rather than adhere to a ‘one-size-fits-all’ approach. 2. Inhalation airflows: children are not miniature adults