Aerosol mechanics in replicas of extrathoracic airways of infants and children

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Deposition of inhaled aerosols in children is of increasing interest, partly due to advances in aerosol inhalation therapy for treating disease, but also due to increased awareness of the health effects of exposure to environmental aerosols in an increasingly urban population. In order to predict the efficacy of an inhaled pharmaceutical aerosol or to assess inhalation dosimetry of an environmental aerosol, it is necessary to first predict the amount of aerosol depositing in the extrathoracic region (consisting of the nose, or mouth, and throat). Unfortunately, little data is available in children to develop validated mathematical models for this purpose, largely because of a lack of data on which to base such models. To address this lack of knowledge, in the present application we propose to build physical replicas of pediatric extrathoracic airways and then measure monodisperse aerosol deposition in these bench-top replicas. Numerical simulation (computational fluid dynamics) will be used to supplement the experimental work. Similar experimental and computational work done by us in adults allowed development of dimensionless correlations that predict extrathoracic deposition in individual subjects with good accuracy. We propose to develop similar subject-specific correlations for children. The result of this work will be algebraic dimensionless equations that can be used to predict, a priori, extrathoracic doses to individual children. In addition to the above, we propose to develop idealized physical models of pediatric airways that can be used in bench-top testing for the development of pharmaceutical aerosols. Similar work by us in adults has resulted in an idealized mouth-throat geometry that is widely used by companies in device and formulation development.