Frictional resistance sheds light on the multicomponent nature of nasal obstruction: A combined in vivo and computational fluid dynamics study

Background Past studies reported a low correlation between rhinomanometry and computational fluid dynamics (CFD), but the source of the discrepancy was unclear. Low correlation or lack of correlation has also been reported between subjective and objective measures of nasal patency. Objective: This study investigates (1) the correlation and agreement between nasal resistance derived from CFD (RCFD) and rhinomanometry (RRMN), and (2) the correlation between objective and subjective measures of nasal patency. Methods Twenty-five patients with nasal obstruction underwent anterior rhinomanometry before and after mucosal decongestion with oxymetazoline. Subjective nasal patency was assessed with a 0-10 visual analog scale (VAS). CFD simulations were performed based on computed tomography scans obtained after mucosal decongestion. To validate the CFD methods, nasal resistance was measured in vitro (REXPERIMENT) by performing pressure-flow experiments in anatomically accurate plastic nasal replicas from 6 individuals. Results Mucosal decongestion was associated with a reduction in bilateral nasal resistance (0.34 ± 0.23 Pa.s/ml to 0.19 ± 0.24 Pa.s/ml, p = 0.003) and improved sensation of nasal airflow (bilateral VAS decreased from 5.2 ± 1.9 to 2.6 ± 1.9, p < 0.001). A statistically significant correlation was found between VAS in the most obstructed cavity and unilateral airflow before and after mucosal decongestion (r = −0.42, p = 0.003). Excellent correlation was found between RCFD and REXPERIMENT (r = 0.96, p < 0.001) with good agreement between the numerical and in vitro values (RCFD/REXPERIMENT = 0.93 ± 0.08). A weak correlation was found between RCFD and RRMN (r = 0.41, p = 0.003) with CFD underpredicting nasal resistance derived from rhinomanometry (RCFD/RRMN = 0.65 ± 0.63). A stronger correlation was found when unilateral airflow at a pressure drop of 75 Pa was used to compare CFD with rhinomanometry (r = 0.76, p < 0.001). Conclusion CFD and rhinomanometry are moderately correlated, but CFD underpredicts nasal resistance measured in vivo due in part to the assumption of rigid nasal walls. Our results confirm previous reports that subjective nasal patency correlates better with unilateral than with bilateral measurements and in the context of an intervention.

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Comprehensive validation of computational fluid dynamics simulations of in-vivo blood flow in patient-specific cerebral aneurysms

Medical Physics ◽

10.1118/1.3675402 ◽

2012 ◽

Vol 39 (2) ◽

pp. 742-754 ◽

Cited By ~ 23

Author(s):

Qi Sun ◽

Alexandra Groth ◽

Til Aach

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Blood Flow ◽

Cerebral Aneurysms ◽

Patient Specific ◽

Computational Fluid Dynamics Simulations ◽

Dynamics Simulations

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Computational fluid dynamics with imaging of cleared tissue and of in vivo perfusion predicts drug uptake and treatment responses in tumours

Nature Biomedical Engineering ◽

10.1038/s41551-018-0306-y ◽

2018 ◽

Vol 2 (10) ◽

pp. 773-787 ◽

Cited By ~ 36

Author(s):

Angela d’Esposito ◽

Paul W. Sweeney ◽

Morium Ali ◽

Magdy Saleh ◽

Rajiv Ramasawmy ◽

...

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Drug Uptake ◽

Treatment Responses

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Microfabricated Cavities for Adhesive Capture of Stem Cells Under Flow

ASME 5th International Conference on Nanochannels, Microchannels, and Minichannels ◽

10.1115/icnmm2007-30177 ◽

2007 ◽

Cited By ~ 2

Author(s):

Dooyoung Lee ◽

Kuldeepsinh Rana ◽

Karin Lee ◽

Lisa A. DeLouise ◽

Michael R. King

Keyword(s):

Fluid Dynamics ◽

Stem Cells ◽

Computational Fluid Dynamics ◽

Blood Flow ◽

Shear Stresses ◽

Computational Fluid Dynamics Cfd ◽

Future Work ◽

Flow Experiments

In previous work, we have described the adhesive capture of circulating stem cells to surfaces coated with adhesive selectin protein, both in vitro and in vivo. Here we describe PDMS surfaces microfabricated to contain an array of square 80 × 80 × 80 micron cavities. These cavities are intended to provide a local bioreactor environment to culture stem cells over extended periods of time, while sheltered from the higher shear stresses of the surrounding blood flow external of the cavities. In this paper we present in vitro flow experiments with polymeric, blood cell-sized microspheres, showing the creation of stable vortices within the microscale cavities. Computational fluid dynamics (CFD) was performed to predict the velocity field within the cavity, and for comparison with experimentally determined microsphere velocities. Future work will establish the ability to place local chemoattract molecules within the cavity interior, and the ability to accumulate viable stem cells within these cavities.

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Investigation of Wall Shear Stress Over an Early Atherosclerotic Plaque in the Left Coronary Artery of a Patient by Intravascular Ultrasound and Computational Fluid Dynamics

ASME 2009 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2009-204121 ◽

2009 ◽

Author(s):

Jin Suo ◽

Michael McDaniel ◽

Saurabh Dhawan ◽

Habib Samady ◽

Don Giddens

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Coronary Artery ◽

Intravascular Ultrasound ◽

Atherosclerotic Plaque ◽

Left Coronary Artery ◽

Invasive Coronary Angiography ◽

Local Flow ◽

Measured Flow

A small isolated region with mild atherosclerotic thickening in the left anterior descending (LAD) coronary artery was identified in a relatively young patient using invasive coronary angiography. The left main (LM) coronary artery and LAD were reconstructed based on biplanar angiography images and intravascular ultrasound (IVUS). The flow field in the lumen was simulated by computational fluid dynamics (CFD) with Doppler-measured flow boundary conditions. The results offer insight into the local flow environment in the neighborhood of an early atherosclerotic plaque in a specific human subject under in vivo conditions. The investigation is continuing with other patients who have mild plaques in the left coronary artery in an effort to elucidate in vivo atherogenesis.

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Computational fluid dynamics applied to the ventilation of small-animal laboratory cages

Laboratory Animals ◽

10.1177/0023677220937718 ◽

2020 ◽

pp. 002367722093771

Author(s):

Ira Katz ◽

Kateryna Voronetska ◽

Mickaël Libardi ◽

Matthieu Chalopin ◽

Patricia Privat ◽

...

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Noble Gas ◽

Small Animal ◽

Toxicity Testing ◽

Exposure Period ◽

In Vitro Models ◽

Gas Distribution

Several studies based on in vivo or in vitro models have found promising results for the noble gas argon in neuroprotection against ischaemic pathologies. The development of argon as a medicinal product includes the requirement for toxicity testing through non-clinical studies. The long exposure period of animals (rats) during several days results in technical and logistic challenges related to the gas administration. In particular, a minimum of 10 air changes per hour (ACH) to maintain animal welfare results in extremely large volumes of experimental gas required if the gas is not recirculated. The difficulty with handling the many cylinders prompted the development of such a recirculation-based design. To distribute the recirculating gas to individually ventilated cages and monitor them properly was deemed more difficult than constructing a single large enclosure that will hold several open cages. To address these concerns, a computational fluid dynamics (CFD) analysis of the preliminary design was performed. A purpose-made exposure chamber was designed based on the CFD simulations. Comparisons of the simulation results to measurements of gas concentration at two cage positions while filling show that the CFD results compare well to these limited experiments. Thus, we believe that the CFD results are representative of the gas distribution throughout the enclosure. The CFD shows that the design provides better gas distribution (i.e. a higher effective air change rate) than predicted by 10 ACH.

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Abstract 2800: Assessment of Computational Fluid Dynamics to Calculate Individual Coronary Wall Shear Stress In-Vivo

Circulation ◽

10.1161/circ.118.suppl_18.s_777-b ◽

2008 ◽

Vol 118 (suppl_18) ◽

Author(s):

Johannes Rieber ◽

Thomas Redel ◽

Holger Hetterich ◽

Tobias Potzger ◽

Konstantin Nikolaou ◽

...

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Shear Stress ◽

Coronary Angiography ◽

Wall Shear Stress ◽

Radio Frequency ◽

Intravascular Ultrasound ◽

Coronary Arteries ◽

Wall Shear

Beyond classic risk parameters non physiologic or oscillating wall shear stress (WSS) has been proven to act as a local factor for initiation and progression of atherosclerosis as well as for plaque rupture. Direct measurement of WSS in-vivo is difficult and restricted to animal models. Computational fluid dynamics (CFD) is a validated tool to compute flow parameters and WSS. For this purpose an exact model of the underlying patient specific geometry of the coronary tree is a prerequisite. Using 3D-IVUS or modern multislice computed tomographic coronary angiography (CTA) with submilimeter resolution these data can be provided. The aim of this study was to 1.) demonstrate feasibility of in-vivo CFD calculation of human coronaries based on CTA and 2.) to correlate the findings with radio frequency tissue information derived by intravascular ultrasound. We prospectively included 10 patients with suspected coronary artery disease who received CTA (Dual source 64 slice CT) and invasive conventional coronary angiography. Intravascular ultrasound and ECG-triggered radio frequency analysis (VH) was attempted in all three epicardial vessels. In the CTA-dataset the coronaries were segmented and a mesh model for CFD was generated. CFD calculations were performed using a commercial available software package with laminar flow and blood as a Newtonian fluid as boundary conditions. Coronary models were stationary with rigid vessel walls, while the pulsatile inflow characteristics was derived from invasive Doppler velocity measurement. Flow pattern calculations, vessel wall shear stress and IVUS analysis were successfully performed in 24/30 and 17/30 coronary arteries. The presence of high shear stress and non turbulent flow was inversely correlated with the presence of plaque as determined by intravascular ultrasound. No correlation of any CFD parameter with the radio frequency tissue information could yet be observed. The findings of the present study demonstrate the feasibility of assessing fluid tissue interactions in human coronary arteries using CTA and its correlation to invasive findings. The possible impact of CFD parameters on risk- and treatment stratification has to be determined in a large scale prospective trial.

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