A general, algebraic equation for predicting total respiratory tract deposition of micrometer-sized aerosol particles in humans

Prediction of the total respiratory tract deposition fraction of an inhaled aerosol is useful in assessing its potential inhalation health risk, or its therapeutic benefit. In this communication, a simple algebraic formulation is presented through which the total deposition fraction can be predicted from dynamical, dimensionless parameters governing inertial and gravitational deposition of inhaled micrometer-scale particles. An empirical fit is first made to the total deposition fraction data of Heyder et al. [1986. Deposition of particles in the human respiratory tract in the size range 0.005–15μm. Journal of Aerosol Science, 17, 811–825] and Kim and Hu [2006. Total respiratory tract deposition of fine micrometer-sized particles in healthy adults: Empirical equations for gender and breathing pattern. Journal of Applied Physiology, 101, 401–412] for healthy adults, during controlled oral breathing of monodisperse micrometer-scale particles. The generality of the resulting formulation based on such dimensionless parameters is then examined by its ability to predict total deposition data measured in children [Schiller-Scotland, C. H. F., Hlawa, R., Gebhart, J., Wönne, R., & Heyder, J. (1992). Total deposition of aerosol particles in the respiratory tract of children during spontaneous and controlled mouth breathing. Journal of Aerosol Science, 23   (Suppl. 1), S457–S460], in microgravity and hypergravity [Darquenne, C., Paiva, M., West, J. B., & Prisk, G. K. (1997). Effect of microgravity and hypergravity on deposition of 0.5- to 3-μmμm-diameter aerosol in the human lung. Journal of Applied Physiology, 83, 2029–2036], and in heliox as an alternative carrier gas [Darquenne, C., & Prisk, G. K. (2004). Aerosol deposition in the human respiratory tract breathing air and 80:20 heliox. Journal of Aerosol Medicine, 17, 278–285]. A single dimensionless correlation is found to provide reasonable prediction of total deposition in all these diverse cases.