In vitro deposition of micrometer-sized particles in the extrathoracic airways of children during tidal oral breathing

Nine oral airway replicas of children 6–14 years old were used for measuring deposition of 0.5–6.3 μm diameter particles during inhalation of four representative (sinusoidal) breathing patterns typical of those observed during the use of nebulizers by children. For a given particle size and inhalation flow rate, deposition in the present child replicas is higher than in adults and is not well predicted by adult correlations, even when age-related scaling factors are applied. However, by using subject-specific geometrical dimensions of the airway replicas, dimensionless correlations that predict deposition of micrometer-sized particles in childrenʹs oral airways during tidal breathing are presented. Such best fitting correlation gives deposition efficiency η 2 = [ 1 − 1 / ( 4.99 ( stk R 2.41 e − 0.17 ) + 1 ) ] × 100 , where Re and Stk are Reynolds and Stokes numbers with length scale given by V/As where V is airway volume and As is airway surface area.