DDT Issue1 Oct '02

Transportation and deposition of droplets from a nebulizer within the nasal cavity are dependent on the existing airflow patterns. Figure 1 illustrates the inspired air profile, which is the dominant airflow pattern in the cavity. Inspired air patterns largely determine where and how drug deposition in the nasal cavity occurs. Relatively low flow amounts are observed in the olfactory region (<10% of the inspired air) and in the nasal meatuses. This is predominately due to the small cross-sectional area of these regions, relative to the total cross-sectional area of the entire nasal cavity. These factors make it difficult to deliver drugs to these regions. In a recent study examining airflow patterns in the nasal cavity, the greatest airflow velocities were observed between the top of the palate and under the inferior turbinate. Velocities and flows decrease in the upper regions of the nasal cavity. The inferior airway has a relatively small crosssectional area, compared to the anterior portion of the cavity, which increases the velocity of the inspired air. The acceleration of the air through the inferior airway forces the inhaled airflow to become more streamlined such that the airflow itself (and any particles carried by the flow) will also tend to move in a predominantly streamwise direction, ie, a direction aligned with the primary flow direction along the axis of the inferior airway. It is desirable to disrupt the axial streamlined trajectories of inhaled particles flowing along the inferior airway. An effective delivery method has to create an environment in which the spatial Controlled Particle DispersionTM: Applying Vortical Flow to Optimize Nasal Drug Deposition By: Marc Giroux, Peter Hwang, MD; and Ajay Prasad, PhD