Development of new respirator using the Taylor dispersion effect

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High frequency oscillation is the artificial respiratory method using a smaller tidal volume than the dead space and high frequency. As this method can be hardly explained by convection transport because of the small tidal volume, Taylor dispersion is considered to be one of the most important mechanisms, that is an interaction between axial convection and lateral mixing. However, it is not obvious how Taylor dispersion plays a role for the gas transport in actual airways. The purpose of this study is to examine the contribution of Taylor dispersion during high-frequency oscillation to elucidate the gas transport phenomena with experimental investigation of velocity profiles and effective diffusivities in the oscillatory flow in the airway model. Finally we develop the design of efficient artificial respirator with high-frequency oscillation. Especially, the effect of lateral mixing on the axial gas transport is examined that is depend upon the flow state that dominates Taylor dispersion.Firstly, the airway model is modified to the straight pipe emerging the resonance. The effective gas diffusivity in the axial direction is enhanced with the presence of turbulence near the resonant frequency. Secondly, the airway model is modified to the asymmetrical and asymmetrical bifurcation modeling the averaged geometry of bifurcation in the airways. The effective gas diffusivity is again augmented due to the secondary flow induced in the bifurcation sites. Thus the augmented gas dispersion effect is utilized to develop the efficient artificial respirator.