Flow limitation on expiration induces central particle deposition and disrupts effective flow of airway mucus

To evaluate the effects of dynamic compression of central lung airways on deposition and retention pattern of insoluble particles in the lung, healthy subjects (n=12) performed respiratory manoeuvres during and previous to, particle inhalations. Particles, 4-6 μm EAD, were radiolabelled and imaged non-invasively in the thorax by Anger camera. Forced expiratory manoeuvres shifted distributions of particle deposition into central regions; distributions of particle deposition were more diffuse when inhalational volumes were on average > 60% of the subject’s inspiratory capacity. Coughing manoeuvres, previous to particle inhalations, had a subsequent influence on airway mucociliary function. The average clearance times of particles from the lung were increased by 37% on post-cough test days as compared to control tests; regional analysis indicated that mucus flow through juxtahilar airways was delayed, but that peripheral transport of mucus into these airways was normal. These data suggest that a causal relationship may exit between compression of large bronchi during forced expiratory manoeuvres and 1) hyperdeposition of aerosol in central lung regions and 2) reduced mucociliary function of juxtahilar airways.