Realistic transparent human airway model: flow distribution and aerosol transport under steady and unsteady flows

článek ve sborníku ve WoS nebo Scopus

angličtina

Better understanding of transport, penetration and deposition of particles in the human lungs is needed to comprehend the health effects of atmospheric particulate matter as well as to increase transport efficiency of therapeutic drugs. Comparisons of studies done on idealized lung geometry with investigations made on more realistic models have shown an influence of complex actual geometry and rough airway surface on flow and particle transport. Several works show important difference between particle transport and deposition characteristics under steady and oscillatory flow conditions. To enable optical measurement of aerosol transport with air as working fluid, we created realistic thin-walled transparent airway model. The non-symmetric bifurcation model reflects real non-planar lung geometry and spans from throat to 3rd-4th generation of bronchi. A pneumatic mechanism generated oscillating air flow into the model. Monodisperse aerosol particles were mixed with air at the model entry. Velocity and size measurement of the particles were done using Phase/Doppler Particle Analyser (P/DPA). Difference between air supply from the "mouth side" and the alveoli side into simple bifurcation lung model was investigated. We observed increased value of turbulence intensity especially during expiration phase in case of the mouth side control compared to alveoli side control. The reason of this distinction is different pressure conditions what leads to altered conditions of turbulence generation. Our model (BUT model) and realistic model by Cheng et al. (1997) (LRRI model) were used for study of flow distribution into particular lung branches at three steady flow regimes: 15, 30 and 90 l/min. Significant differences were found in flow rate distribution into the individual branches of each model and also between both the models. Three oscillatory flow regimes were studied afterwards: tidal volume 0.5 liter and breathing period 4 s, 1 liter & 2 s and 1.875 liter & 1.25 s. Results of flow distribution variability in the LRRI model were similar to the above mentioned results for steady regimes. Results for BUT model differed more significantly from the results at steady regimes. A P/DPA measurement of aerosol transport in trachea was made for tidal volume 1 liter and breathing period 2 s. Mean axial velocity followed the harmonic course of generated flow. Turbulence level was found lower in the inspiration then in the expiration part of the cycle. The turbulence was relatively constant through both the half cycles with exception in the time instants where the droplet velocity direction changed.

Flow distribution, flow velocity, realistic model, human airway

JEDELSKÝ, J.; LÍZAL, F.; JÍCHA, M.

2009

7. 7. 2009

Victoria BC

978-1-55058-404-2

Proceedings of 20th International Symposium on Transport Phenomena

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