Understanding regional aerosol deposition in pediatric airways during oral breathing: Insights from computational modeling

Abstract

While there has been considerable investigation into the deposition of inhaled aerosols in the airways of adults, less is known about where aerosols deposit in the lungs of children. Clinical investigation into aerosol deposition in children is complicated by ethical concerns surrounding ionizing radiation studies in children. To meet the need for non-clinical methods of estimating regional deposition in pediatric airways, multiple in silico models were developed to represent the lungs of girls and boys aged 6, 8, 10 and 12 years. The models were symmetric and used a single-path deterministic approach to calculate aerosol deposition in the airways. Regional deposition estimates were provided for children using a fixed set of controlled breathing patterns before characterizing regional deposition during typical tidal breathing in each age group. Deposition patterns were found to be strongly influenced by inhalation flow rate and aerodynamic particle size. Differences between boys and girls in the fraction of inhaled aerosol depositing were minimal during fixed breathing patterns, with higher deposition in all regions of the younger age groups. However, when breathing patterns were adjusted to represent typical tidal breathing in each age group, age differences in the regional fraction of particles depositing became negligible. Moreover, peak deposition fractions in both the conducting and peripheral airways occurred within a narrow range of aerodynamic particle diameters between 2.4 and 2.6 μm, a smaller size range than for adults. During exposure over a fixed period of time, age-related differences in minute ventilation resulted in a larger aerosol dose depositing in the intrathoracic airways of older children. Such differences suggest that to achieve comparative dosing in this age range, older children should inhale aerosols for a shorter time. These findings provide an improved understanding of regional deposition in pediatric airways and will assist in optimizing regional drug delivery to children.