REGIONAL DEPOSITION OF INHALED HYGROSCOPIC AEROSOLS - IN-VIVO SPECT COMPARED WITH MATHEMATICAL-MODELING

The regional deposition patterns of inhaled hygroscopic aerosols obtai ned in vivo in the studies of Phipps et al. (P. R Phipps, I. Gonda, D. L. Bailey, P. Borham, G. Bautovich, and S. D. Anderson. Am. Rev. Resp ir. Dis. 139: 1516, 1989; and P. R. Phipps, I. Gonda, S. D. Anderson, D. L. Bailey, and G. Bautovich. Eur. Respir. J. 7: 1474-1482, 1994) an d Chan et al. (H.-K. Chan, P. R. Phipps, I. Gonda, P. Cook, R. Fulton, I. Young, and G. Bautovich. Eur. Respir. J. 7: 1483-1489, 1994) by us ing single-photon-emission computerized tomography (SPECT) are compare d with the regional deposition predicted by the hygroscopic lung depos ition model of Finlay and Stapleton (W. H. Finlay and K, W. Stapleton. J. Aerosol Sci. 26: 655-670, 1995). Three pairs of saline aerosols ar e considered: isotonic with small [2.6-mu m mass median aerodynamic di ameter (MMAD), geometric standard deviation (GSD) 1.4] vs. large (5.5- mu m MMAD, GSD 1.7) droplets; hypotonic (0.3% NaCl) vs. hypertonic (4. 5% NaCl) with 3.7- to 3.8 mu m MMAD (GSD 1.4), and hypotonic vs. hyper tonic (3.7- to 3.8-mu m MMAD, GSD 1.5-1.8) with reduced number of drop lets per cubic centimeter For each of the three pairs of aerosols, no significant difference (P > 0.05) was found between thrill vivo and co mputational results for either the mean value or the variance of the d ifference in peripheral to central deposition. Thus it appears that th eoretical calculations can be used to predict the pattern of lung depo sition of hygroscopic aerosols in populations of normal subjects.