Assessment of nasal resistance using computational fluid dynamics

AbstractAnterior rhinomanometry is the current gold standard for the objective assessment of nasal breathing by determining the nasal resistance. However, computational fluid dynamics would allow spatially and temporally well- resolved investigation of additional flow parameters. In this study, measured values of nasal resistance are compared with measured values. An unclear discrepancy between the two methods was found, suggesting further investigation.

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Rhinomanometry Versus Computational Fluid Dynamics: Correlated, but Different Techniques

American Journal of Rhinology and Allergy ◽

10.1177/1945892420950157 ◽

2020 ◽

pp. 194589242095015

Author(s):

Giancarlo B. Cherobin ◽

Richard L. Voegels ◽

Fábio R. Pinna ◽

Eloisa M. M. S. Gebrim ◽

Ryan S. Bailey ◽

...

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Nasal Resistance ◽

Nasal Patency ◽

Low Correlation ◽

Before And After ◽

Computational Fluid Dynamics Cfd ◽

Flow Experiments

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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Computational fluid dynamics endpoints to characterize obstructive sleep apnea syndrome in children

Journal of Applied Physiology ◽

10.1152/japplphysiol.00746.2013 ◽

2014 ◽

Vol 116 (1) ◽

pp. 104-112 ◽

Cited By ~ 38

Author(s):

David M. Wootton ◽

Haiyan Luo ◽

Steven C. Persak ◽

Sanghun Sin ◽

Joseph M. McDonough ◽

...

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Obstructive Sleep Apnea ◽

Sleep Apnea ◽

Obstructive Sleep Apnea Syndrome ◽

Sleep Apnea Syndrome ◽

Nasal Resistance ◽

Cfd Model ◽

Obstructive Sleep ◽

Apnea Syndrome

Computational fluid dynamics (CFD) analysis may quantify the severity of anatomical airway restriction in obstructive sleep apnea syndrome (OSAS) better than anatomical measurements alone. However, optimal CFD model endpoints to characterize or assess OSAS have not been determined. To model upper airway fluid dynamics using CFD and investigate the strength of correlation between various CFD endpoints, anatomical endpoints, and OSAS severity, in obese children with OSAS and controls. CFD models derived from magnetic resonance images were solved at subject-specific peak tidal inspiratory flow; pressure at the choanae was set by nasal resistance. Model endpoints included airway wall minimum pressure (Pmin), flow resistance in the pharynx (Rpharynx), and pressure drop from choanae to a minimum cross section where tonsils and adenoids constrict the pharynx ( dP TAmax). Significance of endpoints was analyzed using paired comparisons ( t-test or Wilcoxon signed rank test) and Spearman correlation. Fifteen subject pairs were analyzed. Rpharynx and dP TAmax were higher in OSAS than control and most significantly correlated to obstructive apnea-hypopnea index (oAHI), r = 0.48 and r = 0.49, respectively ( P < 0.01). Airway minimum cross-sectional correlation to oAHI was weaker ( r = −0.39); Pmin was not significantly correlated. CFD model endpoints based on pressure drops in the pharynx were more closely associated with the presence and severity of OSAS than pressures including nasal resistance, or anatomical endpoints. This study supports the usefulness of CFD to characterize anatomical restriction of the pharynx and as an additional tool to evaluate subjects with OSAS.

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Objective Assessment of the Breathe-Right Device during Exercise in Adult Males

American Journal of Rhinology ◽

10.2500/105065897781286061 ◽

1997 ◽

Vol 11 (5) ◽

pp. 393-398 ◽

Cited By ~ 23

Author(s):

Louis G. Portugal ◽

Rajeev H. Mehta ◽

Bonnie E. Smith ◽

Jaishiri B. Sabnani ◽

Matthew J. Matava

Keyword(s):

African American ◽

Objective Assessment ◽

Acoustic Rhinometry ◽

Nasal Airway ◽

Nasal Resistance ◽

Adult Males ◽

Nasal Breathing ◽

Cross Sectional ◽

American Group ◽

Paradoxical Worsening

In order to improve nasal breathing during competition, many athletes recently have been wearing a spring-loaded, external nasal dilator referred to as the Breathe-Right device (BRD). Although there are many subjective claims that this device improves breathing during exercise, there are currently no controlled studies documenting its efficacy. To determine objectively whether the device improves the nasal airway, 20 subjects (10 Caucasian and 10 African-American) were studied during rest and after 15 minutes of exercise using anterior rhinomanometry and acoustic rhinometry to measure changes in airway resistance and minimal cross-sectional area, respectively. We found that the BRD exerts its main effect in the region of the nasal valve improving the airway an overall 21% in our group of subjects. This anatomic improvement in nasal airway resulted in an overall 27% reduction in nasal resistance in the Caucasian group. However, in the African-American group, a wider range of resistance changes was observed with application of the BRD with significant improvement in nasal resistance in some subjects but paradoxical worsening in others. In the African-American group as a whole, no significant change in nasal resistance occured with application of the BRD. These measured differences are likely due to variations in nasal anatomy that exist not only between races but also between individuals within a given race. In addition, this study confirms the well known decongestant effects of exercise providing anatomic data with acoustic rhinometry not previously documented in the literature. Overall improvement in nasal airway seen with application of the BRD occured independent of these exercise-related decongestant effects.

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Analysis of conductive olfactory dysfunction using computational fluid dynamics

PLoS ONE ◽

10.1371/journal.pone.0262579 ◽

2022 ◽

Vol 17 (1) ◽

pp. e0262579

Author(s):

Youji Asama ◽

Akiko Furutani ◽

Masato Fujioka ◽

Hiroyuki Ozawa ◽

Satoshi Takei ◽

...

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Maximum Flow ◽

Olfactory Dysfunction ◽

Mouth Breathing ◽

Respiratory Physiology ◽

Research Assessment ◽

Nasal Breathing ◽

Olfactory Cleft ◽

Scan Data

Conductive olfactory dysfunction (COD) is caused by an obstruction in the nasal cavity and is characterized by changeable olfaction. COD can occur even when the olfactory cleft is anatomically normal, and therefore, the cause in these cases remains unclear. Herein, we used computational fluid dynamics to examine olfactory cleft airflow with a retrospective cohort study utilizing the cone beam computed tomography scan data of COD patients. By measuring nasal–nasopharynx pressure at maximum flow, we established a cut-off value at which nasal breathing can be differentiated from combined mouth breathing in COD patients. We found that increased nasal resistance led to mouth breathing and that the velocity and flow rate in the olfactory cleft at maximum flow were significantly reduced in COD patients with nasal breathing only compared to healthy olfactory subjects. In addition, we performed a detailed analysis of common morphological abnormalities associated with concha bullosa. Our study provides novel insights into the causes of COD, and therefore, it has important implications for surgical planning of COD, sleep apnea research, assessment of adenoid hyperplasia in children, and sports respiratory physiology.

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Computational Fluid Dynamics (CFD) for Modelling Multiphase Flow in Hilly-Terrain Pipelines

Diffusion Foundations ◽

10.4028/www.scientific.net/df.28.33 ◽

2020 ◽

Vol 28 ◽

pp. 33-55

Author(s):

Oluwasanmi Olabode ◽

Gerald Egeonu ◽

Richard Afolabi ◽

Charles Onuh ◽

Chude Okonji

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Multiphase Flow ◽

Gas Production ◽

Design Tool ◽

Production Operation ◽

Hilly Terrain ◽

Qualitative Design ◽

Flow Parameters ◽

Subsea Pipelines

The design and operation of subsea pipelines over the life-cycle of an asset is vital for continuous oil and gas production. Qualitative design and effective production operation of pipelines depend on fluid type(s) involved in the flow; and in the case of multiphase flow, the need to understand the behaviour of the fluids becomes more imperative. This work presented in this report is borne out of the need for more accurate ways of predicting multiphase flow parameters in subsea pipelines with hilly-terrain profiles by better understanding their flow behaviors. To this end, Computational Fluid Dynamics has been used as against existing experimental and mechanistic methods which have inherent shortcomings. The results showed that multiphase flow parameters including flow-regimes, liquid hold-up and pressure drop in hilly-terrain pipelines can be modelled without associated errors in existing techniques. Similarity in trend was found when results of pressure gradient in downward-incline pipe were compared with results from existing correlations and mechanistic method. CFD can be used as a design tool and also a research tool into the understanding of the complexities of multiphase flow in hilly-terrain pipelines towards qualitative design and effective operation of hilly-terrain pipelines.

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Experimental Determination of the Parameters for Modelling Semi-Solid Processing

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.116-117.16 ◽

2006 ◽

Vol 116-117 ◽

pp. 16-23

Author(s):

H.V. Atkinson

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Numerical Modeling ◽

Steady State ◽

Processing Route ◽

Flow Parameters ◽

Properties Of Materials ◽

Semi Solid ◽

Rapid Transients

The numerical modeling of semi-solid processing requires data on the rheological properties of materials. This data is often obtained by rheometry but there are difficulties with characterizing high solid fractions, where the torque which can be exerted with the rheometer is insufficient. A number of other methods for measuring the flow parameters, including compression between platens, have been utilized. The various methods will be reviewed in this paper. Computational fluid dynamics modelers have often used data from steady state experiments but it is the behaviour during rapid transients which is more relevant to the actual semi-solid processing route.

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An Overview of Computational Fluid Dynamics Preoperative Analysis of the Nasal Airway

Facial Plastic Surgery ◽

10.1055/s-0041-1722956 ◽

2021 ◽

Author(s):

Rui Xavier ◽

Dirk-Jan Menger ◽

Henrique Cyrne de Carvalho ◽

Jorge Spratley

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Surgical Techniques ◽

Virtual Surgery ◽

Nasal Airway ◽

Cfd Analysis ◽

Nasal Airflow ◽

Nasal Breathing ◽

Objective Measurements ◽

Patient Reported

AbstractEvaluation of the nasal airway is crucial for every patient with symptoms of nasal obstruction as well as for every patient with other nasal symptoms. This assessment of the nasal airway comprises clinical examination together with imaging studies, with the correlation between findings of this evaluation and symptoms reported by the patient being based on the experience of the surgeon. Measuring nasal airway resistance or nasal airflow can provide additional data regarding the nasal airway, but the benefit of these objective measurements is limited due to their lack of correlation with patient-reported evaluation of nasal breathing. Computational fluid dynamics (CFD) has emerged as a valuable tool to assess the nasal airway, as it provides objective measurements that correlate with patient-reported evaluation of nasal breathing. CFD is able to evaluate nasal airflow and measure variables such as heat transfer or nasal wall shear stress, which seem to reflect the activity of the nasal trigeminal sensitive endings that provide sensation of nasal breathing. Furthermore, CFD has the unique capacity of making airway analysis of virtual surgery, predicting airflow changes after trial virtual modifications of the nasal airway. Thereby, CFD can assist the surgeon in deciding surgery and selecting the surgical techniques that better address the features of each specific nose. CFD has thus become a trend in nasal airflow assessment, providing reliable results that have been validated for analyzing airflow in the human nasal cavity. All these features make CFD analysis a mainstay in the armamentarium of the nasal surgeon. CFD analysis may become the gold standard for preoperative assessment of the nasal airway.

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