Regional deposition of saline aerosols of different tonicities in normal and asthmatic subjects

Abstract

R Re eg gi io on na al l d de ep po os si it ti io on n o of f s sa al li in ne e a ae er ro os so ol ls s o of f d di if ff fe er re en nt t t to on ni ic ci it ti ie es s i inABSTRACT: 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 tonicities. 99m Technetium-diethyltriaminepentaacetic acid ( 99m Tc-DTPA)-labelled saline aerosols, with mass median aerodynamic diameter 3.7-3.8 µm and geometric standard deviation 1.4, were inhaled under reproducible breathing conditions on two occasions. Hypotonic and hypertonic solutions were used in 11 normals subjects, isotonic and hypertonic solutions in 9 asthmatics. The regional deposition was quantified by a penetration index measured with the help of a tomographic technique.There was a small but significant increase (6.7%) in the penetration index of the hypotonic as compared to the hypertonic aerosols in the normal subjects. The region that was markedly affected was the trachea. The differences in the penetration of the isotonic and hypertonic aerosols in the asthmatics appeared to be strongly dependent on 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 nonisotonic aerosols, as well as of airway narrowing, on regional deposition of aerosols. Tonicity of aerosols appears to affect their deposition both through physical and physiological mechanisms. This should be taken into account when interpreting the effects of inhaled aqueous solutions of various tonicities in patients in vivo.

Regional deposition of nebulized hypodense nonisotonic solutions in the human respiratory tract

“…The differences observed between the deposition of hypo-and hypertonic nebulized solutions in normal subjects were somewhat less than expected on theoretical grounds [23]. One possible explanation for this discrepancy was that, during the inhalation, the aerosols significantly change the composition of the airway fluid such that the driving force for the hypertonic aerosol to grow, or for the hypotonic aerosol to shrink, is reduced.…”

“…As in our previous studies [22,23], precautions were taken, by using humidified dilution air [24,26,35], to prevent droplet evaporation before entry of the aerosol to the mouth. This was confirmed by collection of aerosol and assuring that the osmolarity of the collected solution was the same as that of the solution in the nebulizer.…”

“…The subjects inhaled on two separate occasions under controlled breathing conditions either 5 or 0.3% radiolabelled aqueous saline aerosols (in one study without, and in the second study with, 0.5% nedocromil sodium). The regional deposition of the radioaerosol was followed by external scintigraphy [22,23].…”

“…Single photon emission computerized tomography (SPECT) [22] was used to investigate the distribution of aerosols "in vivo" of nonisotonic saline solutions prepared by conventional nebulizers [23][24][25][26]. The differences observed between the deposition of hypo-and hypertonic nebulized solutions in normal subjects were somewhat less than expected on theoretical grounds [23].…”

Inhaled chemotherapy in lung cancer: future concept of nanomedicine

“…The increase in particle size above the initial size should affect the amount of drug deposited and, particularly, distribution of the aerosolized drug within the lung. 65,66 Further drug absorption could occur via the lymphatic pathway. 67,68 …”