Summary: Computational fluid dynamics modeling of extrathoracic airway flush: evaluation of high flow nasal cannula design elements.

Topic: Flush

Miller T, Saberi B, Saberi S Computational fluid dynamics modeling of extrathoracic airway flush: evaluation of high flow nasal cannula design elements. J Pulm Respir Med. 2026;6:376. Doi:10.4172/2161-105X.1000376 

Miller and colleagues conducted an in silico computational study to evaluate the fluid patterns in the human nasal and pharyngeal cavities with high flow nasal cannula (HFNC) application and quantified time to purge for two cannula configurations using a computational fluid dynamics (CFD) model. A three-dimensional geometry of the human airway was used to define the extrathoracic dead space and the two cannula designs tested incorporate large vs small bore nasal prong configurations (Vapotherm Flowrest). The fluid flow simulations were performed using FLOW-3D software, set up for a cannula flow rate of 20 L/min and run until steady state. 

Basic flow patterns were similar between cannulae, creating vortices around a central inward flow path. Flow velocity around the vortices was greater with the small prong cannula, resulting in a lower pressure in each region of the nasal and nasopharyngeal space. The calculation of purge time revealed that the small prong nasal cannula was able to clear the nasal, pharyngeal, and oral cavities in 2.2 seconds, whereas the large bore cannula required 3.6 seconds (64% longer).The study limitations are such that this model is computational for one set of airway geometries and cannula positions. Actual variations from person to person with regard to airway geometry, as well as cannula positioning, may influence the reported flow parameters. This study used a static model that did not account for breathing and did not account for expiratory flow from the lungs. 

The researchers concluded that the current CFD data validate that a smaller bore nasal prong facilitates the purge action, which is related to velocity and dynamic energy induced by the tighter prong nozzle as opposed to the lesser occlusion of the nares. 


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