Airway deposition of hygroscopic heterodispersed aerosols: results of a computer calculation.

A new computer model is developed and used to calculate the deposition of inhaled heterodispersed hygroscopic aerosols for mouth breathing in a Weibel symmetric bronchial tree. The model was first validated by obtaining good agreement with recent experimental and theoretical data on regional and total airway deposition of monodispersed and heterodispersed nonhygroscopic aerosols. The model was then used to obtain predictions of regional and total deposition of heterodispersed hygroscopic aerosol particles (droplets of NaCl solutions). Parameters that were varied in the hygroscopic calculations include initial droplet NaCl concentration, time of inspiration and expiration, volume of aerosol inspired, period of breath holding, and initial inhaled lognormal aerosol mass median diameter and geometric standard deviation. Results of the computer calculations show that increasing heterodispersity tends to flatten and broaden regional deposition curves when fraction of inhaled mass deposited is plotted vs. inhaled mass median aerodynamic particle diameter. Hygroscopicity is shown to increase tracheobronchial and pulmonary airway deposition with hypertonic NaCl solution aerosols showing increases over isotonic and nonhygroscopic aerosols of up to 200%.