Aerosol deposition in the nose as a function of body size.

The effect of body size on nasal doses from inhaled aerosols has not been measured directly in people. Two basic types of computational models are used to calculate inhaled particle deposition in adults. One type uses an impaction parameter that incorporates particle aerodynamic diameter and the average airflow rate. The second type uses the nasal pressure drop and particle aerodynamic diameter. Although both types of models have been adjusted to give reasonably accurate deposition efficiencies for adults, they predict very different deposition efficiencies when they are applied to young children. This is not surprising because the airflow-type model has no body-size-dependent parameters, unlike the pressure-drop-type model. The objective of our studies was to test these two types of computational models using idealized hollow nasal models of two sizes, representing the adult and young child. The results indicate that a pressure-drop relationship fits the aerosol deposition data very well. When the properly scaled physiological air flows and minute ventilations are used in a nasal dose calculation, the young child is seen to have potentially larger nasal doses than those of an adult.