Fluid dynamic assessment of positive end-expiratory pressure in a tracheostomy tube connector during respiration

Abstract

High-flow oxygen therapy using a tracheostomy tube is a promising clinical approach to reduce the work of breathing in tracheostomized patients. Positive end-expiratory pressure (PEEP) is usually applied during oxygen inflow to improve oxygenation by preventing end-expiratory lung collapse. However, much is still unknown about the geometrical effects of PEEP, especially regarding tracheostomy tube connectors (or adapters). Quantifying the degree of end-expiratory pressure (EEP) that takes patient-specific spirometry into account would be useful in this regard, but no such framework has been established yet. Thus, a platform to assess PEEP under respiration was developed, wherein three-dimensional simulation of airflow in a tracheostomy tube connector is coupled with a lumped lung model. The numerical model successfully reflected the magnitude of EEP measured experimentally using a lung phantom. Numerical simulations were further performed to quantify the effects of geometrical parameters on PEEP, such as inlet angles and rate of stenosis in the connector. Although sharp inlet angles increased the magnitude of EEP, they cannot be expected to achieve clinically reasonable PEEP. On the other hand, geometrical constriction in the connector can potentially result in PEEP as obtained with conventional nasal cannulae. Graphical abstract

Effect of modified high-flow oxygen therapy on positive end-expiratory pressure and end-expiratory lung volume based on simulated lung platform

“…Two types of resistance valves that matched the high-flow standard interface for exhalation were designed, thereby, further improving the high-flow respiratory humidification therapy device. Meanwhile, previous studies have shown that high-flow oxygen therapy was beneficial for increasing tidal volume and reducing respiratory frequency in COPD patients, thus reducing respiratory effort [ [19] , [20] , [21] ]. However, unlike AHRF, COPD patients themselves have the characteristic of obvious difficulty in exhalation.…”