Aerosol Bolus Dispersion and Recovery in a Human and Dog Airway Cast

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In recent years methods in lung diagnostics have been developed using the aerosolbolus inhalation technique (Heyde etr al., 1988; Anderso n et al., 1989 Schul; z et al.,1995; Blanchard 1996). A bolus is a small volume of aerosol sandwiched inparticle-free air and inhaled into different volumetric regions of the lung. Duringinhalation and exhalation the original small bolus is dispersed over a larger volume.This dispersion is caused by convective mixing in the airways and by intrinsicparticle motion. Because particles in the size range between 0.2 and about 1 umhave low intrinsic motion, they can be used as tracers of the convective air transportin the lungs. The extent of broadening of the bolus measured in the exhaled air is ameasure of the convective mixing during inhalation and exhalation, Blanchard(1996).The bolus inhalation technique can also be used to deliver aerosol into specificvolumetric regions of the lungs. If a bolus is inhaled near the end of an inhalation,the aerosol particles cannot penetrate deep into the lungs and should be deliveredpreferentially to the tracheobronchial airways. In order to determine where theparticles from an inhaled bolus are located within the lungs at end inhalation,dispersion and recovery studies were made in a dog and a human airway cast.