Examining the ability of empirical correlations to predict subject specific in vivo extrathoracic aerosol deposition during tidal breathing

Abstract

The accuracy of five extrathoracic deposition equations was examined by comparing model predictions with in vivo deposition measurements of 99mTc-DTPA radiolabeled 0.9% saline delivered via PARI LC Sprint nebulizers in 19 healthy human subjects. The average extrathoracic deposition fraction measured in vivo was 0.19 ± 0.10 (average ± standard deviation). Comparing to this average value, the extrathoracic deposition fraction predicted by Golshahi et al. equation was the most accurate (0.18 ± 0.08), followed by the model described by the ICRP (0.16 ± 0.03). However, prediction of subject-specific deposition proved more challenging; the Golshahi et al. model performed the best of the examined equations, yet showed only a small positive correlation between measured and predicted deposition in individual subjects with a Pearson correlation coefficient of 0.34. The difficulties in predicting subject-specific deposition likely result from geometric dissimilarity both within and between subjects, and may require more complicated modeling methods than algebraic equations of the kind examined in this study. Copyright © 2017 American Association for Aerosol Research