Particle deposition in children's lungs: theory and experiment.

A mathematical model of inhaled aerosol particle deposition for children is presented and validated with data from two published experimental studies. The model accurately predicts deposition fraction (DF) in children as a function of particle size for particles in the size range 1-3 microns for both sedentary and exercise breathing conditions. When the experimental data are grouped according to age, the model is able to predict age-dependent trends in DF at the studied particle sizes under sedentary breathing conditions. The model predicts that when ventilatory conditions are held constant, age-dependent changes in morphology result in decreasing DF with age; however, under realistic conditions these changes may be masked by age-dependent changes in ventilation. Despite the fact that mean DF differs significantly from adult values only in children younger than 9, the model predicted that dose-per-surface area may still be greater in children due to smaller lung sizes.