CFD analysis of the human airways under impedance-based boundary conditions: application to healthy, diseased and stented trachea

Abstract

A computational fluid dynamics model of a healthy, a stenotic and a post-operatory stented human trachea was developed to study the respiration under physiological boundary conditions. For this, outflow pressure waveforms were computed from patient-specific spirometries by means of a method that allows to compute the peripheral impedance of the truncated bronchial generation, modelling the lungs as fractal networks. Intratracheal flow pattern was analysed under different scenarios. First, results obtained using different outflow conditions were compared for the healthy trachea in order to assess the importance of using impedance-based conditions. The resulted intratracheal pressures were affected by the different boundary conditions, while the resulted velocity field was unaffected. Impedance conditions were finally applied to the diseased and the stented trachea. The proposed impedance method represents an attractive tool to compute physiological pressure conditions that are not possible to extract in vivo. This method can be applied to healthy, pre- and post-operatory tracheas showing the possibility of predicting, through numerical simulation, the flow and the pressure field before and after surgery.

Keywords:

• CFD
• trachea
• bifurcation
• impedance
• stenosis
• stent

Acknowledgements

This study was supported by the CIBER-BBN, an initiative funded by the VI National R&D&i Plan 2008–2011, Iniciativa Ingenio 2010, Consolider Program, CIBER Actions and financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund and by the research project PI07/90023. The technical support of Plataform for Biological Tissue Characterization of the Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN) is highly appreciated. We finally wish to thank Christine M. Scotti (W.L. Gore & Associates, Inc. Flagstaff, AZ, USA).