Experimental study of aerosol deposition in distal lung bronchioles

Abstract

The deposition of micron particles finds importance in meteorology and several engineering applications such as deposition of dust in gas lines, carbon deposition in engine exhaust, designing effective air-cleaning systems and estimating deposition of inhaled drug or atmospheric pollutants to determine its consequences on human health. Although the existing literature on deposition in straight tubes is quite mature, an experimental study on deposition in micro capillaries with a wide ranges of Re that models particle dynamics in lungs, is missing. The deposition of atmospheric pollutants and nebulized drugs in the lung depends on various biological factors such as flow properties, lung morphology, breathing patterns, particle properties, deposition mechanism, etc. To complicate matters, each breath manifests flows spanning a wide range of Reynolds numbers in various regions of the lung. In this study, the deposition of nebulized aerosol was experimentally investigated in phantom bronchioles of diameters relevant to the 7th to the 23rd branching generations and over the entire range of Re manifest during one breathing cycle. The aerosol fluid was loaded with boron doped carbon quantum dots as a fluorophore. An aerosol was generated of this mixture fluid using an ultrasonic nebulizer, producing droplets of 6.5$\mu$m as the mean diameter. The amount of aerosol deposited on the bronchiole walls was measured using a spectrofluorometer. Finally, a universal bronchiole scale deposition model is proposed which can form the building block for lung-scale aerosol deposition prediction.