W. Vos, J. De Backer, S. Vinchurkar, D. Daems, L. De Backer, W.A. De Backer
Introduction: The internal airflow distribution under non invasive ventilation (NIV) is dependent on lobar airway resistance (R) and tissue stiffness (S). A method to calculate these parameters can assist in a better outcome prediction of NIV treatment and improve patients’ treatment compliance. The aim of this study is to calculate lobar R and S using functional imaging updated with computational fluid dynamics (CFD) in a population of hypercapnic COPD patients intended to undergo NIV treatment.
Methods: Persistent hypercapnic COPD gold III patient undergo a low dose CT scan at FRC and TLC. From this scan airway tree and lobar expansion (=internal flow distribution) are obtained. Also a simultaneous respiratory flow and esophageal pressure (peso) measurement is performed. CFD flow simulations using the 3D model, the measured flow rates and internal distribution (blue in figure), are performed to obtain lobar R and lobar pressure (red in figure). The difference in lobar pressure en peso together with lobar inflow are used to calculate lobar S (green in figure)
Results: Results show that the lobar resistance profile has a similar shape as the flow profile. The lobar stiffness profile is constant during expiration. During inspiration the lobar stiffness does increase exponentially near the end of the inspiration. Furthermore it can be seen that both resistance and tissue stiffness do vary significantly between the different lobes.
Conclusions: Lobar airway resistance and stiffness can be obtained through functional imaging using computational fluid dynamics, by taking a CT scan and a simultaneous flow and peso measurement. Information on these lobar properties can be used to predict the outcome non-invasive ventilation.
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European Respiratory Society, 24-28 September 2011, Amsterdam, The Netherlands