Computational Fluid Dynamic Analysis of an Instrumented Endotracheal Tube for Total Liquid Ventilation to Optimize Pressure Transducer Positioning

Abstract

Despite advances in respiratory care, the treatment of critical neonatal patients with conventional mechanical ventilation (CMV) techniques has still many drawbacks. To address this issue, Total Liquid Ventilation (TLV) with liquid perfluorocarbons (PFC) has been investigated as an alternative respiratory modality [1,2]. A dedicated TLV ventilator supplies PFC tidal volumes (TV) through an endotracheal tube (ETT) inserted into the trachea. In experimental studies, TLV proved to be able to support pulmonary gas exchange while preserving lung structure and function. Moreover, PFC properties make these liquids an optimal medium to treat neonatal respiratory failure [1–3]. However, different aspects of TLV have to be further investigated for a safe transition from the laboratory experience to the clinical application. One of these aspects is the possible airway and lung injury that may be caused by the peculiar fluid dynamics developed when using an incompressible and viscous liquid instead of air as a respiratory medium. To overcome this issue, continuous reliable real-time monitoring of airway pressure during TLV is crucial. Thus, the instrumentation of the ETT with a pressure transducer (PT) is mandatory to perform a safe TLV treatment [4–6]. At present, no commercial instrumented ETTs designed for TLV are available; thus during TLV experimental animal trials [4–6] ETT prototypes instrumented with homemade PT-equipped catheters are currently used. However, the positioning of this catheter has to be optimized in order to reduce fluid dynamic disturbances that can alter pressure measurements. Aim of this study is to investigate on the PFC fluid-dynamic patterns in the presence of the catheter by computational fluid dynamic (CFD) analysis, in the view of the development of a TLV dedicated instrumented ETT. In particular, the effect of two different positioning of the PT catheter on the PFC fluid dynamics and airway pressure measurement was evaluated for a neonatal ETT.