Regional ventilation and particle deposition in the healthy and obstructed lung

Persons with obstructive lung diseases have marked ventilatory inhomogeneity relative to healthy controls. This diseased population is also known to have increased total particle deposition with sites of highly localized deposition across all range of inhaled particle sizes relative to healthy controls. It has been suggested that nonuniform ventilation distribution may be an important factor contributing to the production of areas of high particle deposition, capable of overwhelming pulmonary defenses, in persons with obstructive lung diseases. Interestingly, for this same diseased population, there is a preponderance of epidemiological data demonstrating associations between morbidity and mortality and exposure to particulate air pollution. The link between ventilation distribution and particle transport and/or deposition has not been well established, especially in the obstructed lung.; The goal of this research was to investigate the relationship between regional ventilation and particle deposition in man, with particular attention given to this relationship in persons with obstructive lung diseases. Experimental data in patients with cystic fibrosis showed that significant coarse particle (5 μm mass median aerodynamic diameter) deposition may occur in the obstructed airways of poorly ventilated (obstructed) lung regions. Whereas, deposition within the airways and parenchyma of well ventilated (healthy) lung regions may increase with ventilation. Based on a limited number of subjects with normal to mildly obstructed airways, the pattern of deposition for both fine (1.5 μm activity median diameter, AMD) and ultrafine (0.06 μm AMD) aerosols appeared to follow regional ventilation. Particle deposition was mathematically modeled in a diseased lung with partially obstructed airways in one half and fully patent airways in the opposing half. With consideration given to ventilation distribution, modeling showed that experimental findings were, in large part, predictable. Compared to a disease free lung, data show that obstructive airways disease results in an increased surface dose in obstructed as well as unobstructed regions of the lung. The results of this research provide a better understanding of the association between ventilation distribution and the deposition of inhaled aerosols in the obstructed lung.