Comparison of computer simulations of total lung deposition to human subject data in healthy test subjects

A mathematical model was used to predict the deposition fractions (DF) of P M within human lungs. Simulations using this computer model were previously validated with human subject data and were used as a control case. Human i ntersubject variation was accounted for by scaling the base lung morphology dimensions based on measured functional residual capacity (FRC) values. Si mulations were performed for both controlled breathing (tidal volumes [V-ta u] of 500 and 1000 mL, respiratory times [T] from 2 to 8 sec) and spontaneo us breathing conditions. Particle sizes ranged from 1 to 5 mu m. The deposi tion predicted from the computer model compared favorably with the experime ntal data. Far example, when V-tau = 1000 mi, and T = 2 sec, the error was 1.5%. The errors were slightly higher for smaller tidal volumes. Because th e computer model is deterministic (i.e., derived from first principles of p hysics), the model can be used to predict deposition fractions for a range of situations (i.e., for different ventilatory parameters and particle size s) for which data are not available. Now that the model has been validated, it may be applied to risk assessment efforts to estimate the inhalation ha zards of airborne pollutants.