REGIONAL DEPOSITION OF SALINE AEROSOLS OF DIFFERENT TONICITIES IN NORMAL AND ASTHMATIC SUBJECTS

Nonisotonic aerosols are frequently used in the diagnosis and therapy of lung disease. The purpose of this work was to study the difference in the pattern of deposition of aerosols containing aqueous solutions of different icities.(99m)Technetium-diethyltriaminepentaacetic acid ( Tc-99m-DTPA)-labelled saline aerosols, with mass median aerodynamic di ameter 3.7-3.8 mu m and geometric standard deviation 1.4, were inhaled under reproducible breathing conditions on two occasions. Hypotonic a nd hypertonic solutions were used in 11 normals subjects, isotonic and hypertonic solutions in 9 asthmatics. The regional deposition was qua ntified by a penetration index measured with the help of a tomographic technique. There was a small but significant increase (6.7%) in the p enetration index of the hypotonic as compared to the hypertonic aeroso ls in the normal subjects. The region that was markedly affected was t he trachea. The differences in the penetration of the isotonic and hyp ertonic aerosols in the asthmatics appeared to be strongly dependent o n the state of the airways at the time of the study.These findings can be interpreted in terms of effects of growth or shrinkage of nonisoto nic aerosols, as well as of airway narrowing, on regional deposition o f aerosols, Tonicity of aerosols appears to affect their deposition bo th through physical and physiological mechanisms. This should be taken into account when interpreting the effects of inhaled aqueous solutio ns of various tonicities in patients in vivo.