Numerical simulation study on effects of ambient temperature on airflow in the nasal cavity / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To study the aerodynamics of the normal human nasal cavity under different ambient temperatures.</p><p><b>METHODS</b>Based on CT scanning, a model of a healthy adult's nasal cavity was established using computational fluid dynamics software from Fluent. Airflow in this model was simulated and calculated at ambient temperatures of 0 °C, 24 °C, and 37 °C during periodic breathing.</p><p><b>RESULTS</b>Ambient temperature only had an impact on the temperature in the nasal cavity during the inspiratory phase, and the temperature distribution was not symmetrical in the inspiratory acceleration and deceleration phases. The ambient temperature significantly affected airflow speed in main nasal passages during the inspiratory process, but had little impact on flow status (proportion and streamline of airflow in different nasal passages). Temperature differences increased the irregular air movement within sinuses. The anterior nasal segment, including the area between the valve and the head of the middle turbinate, was the most effective part of the nasal airway in heating the ambient air.</p><p><b>CONCLUSIONS</b>Our findings describe the effects of ambient temperature on airflow parameters in the nasal cavity within a single respiratory cycle. This data is more comprehensively and accurately to determine the relationship between nasal cavity aerodynamics and physiological functions.</p>

A comparative study on numerical simulation of the normal nasal airflow during periodic breathing and steady-state breathing / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To compare the characteristics of normal nasal airflow during periodic breathing and steady-state breathing.</p><p><b>METHODS</b>Fluent software was used to simulate the nasal cavity and paranasal sinus structures following CT scanning of a normal adult subject. Air flow velocity, pressure, distribution and streamlines were calculated and compared during periodic breathing and steady-state breathing.</p><p><b>RESULTS</b>The same flux, the performance of nasal airflow on 15.600 s of periodic breathing and steady-state expiratory (entrance flow was 697.25 ml/s) were as follows: air flow in the common and middle meatus accounted for more than 50% and 30% of total nasal cavity flow during two respiratory status. Flow velocity and pressure of nasal cavity and each paranasal sinus were extremely similar. The flow trace during two respiratory status in the inferior and lower part of the common meatus were predominately straight in form.Flow were parabolic in the middle and superior meatus and the middle and upper parts of the common meatus. The flow trace of nasal airflow on 16.495 s of periodic breathing had wide areas vortex in nasopharynx and limen nasi, the average speed was 0.0706 m/s, while the entrance flow 7.62 ml/s stable state of the left nasal expiratory, the average speed was 0.0415 m/s, the flow trace was similar to 697.25 ml/s.</p><p><b>CONCLUSION</b>The same flow, except in the junction of the respiratory cycle, the performance of normal nasal airflow during periodic breathing and steady-state breathing were similar.</p>

Effect of endoscopic sinus surgery on airflow of the nasal cavity and paranasal sinuses: a computational fluid dynamics study / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To study the airflow velocity, trace, distribution, pressure, as well as the airflow exchange between the nasal cavity and paranasal sinuses in a computer simulation of nasal cavity pre and post virtual endoscopic sinus surgery (ESS).</p><p><b>METHODS</b>Computational fluid dynamics (CFD) technique was applied to construct an anatomically and proportionally accurate three-dimensional nasal model based on a healthy adult woman's nasal CT scans. A virtual ESS intervention was performed numerically on the normal nasal model using Fluent 6.1.22 software. Navier-Stokes and continuity equations were used to calculate and compare the airflow characteristics between pre and post ESS models.</p><p><b>RESULTS</b>(1) After ESS flux in the common meatus decreased significantly. Flux in the middle meatus and the connected area of opened ethmoid sinus increased by 10% during stable inhalation and by 9% during exhalation. (2) Airflow velocity in the nasal sinus complex increased significantly after ESS. (3) After ESS airflow trace was significantly changed in the middle meatus. Wide-ranging vortices formed at the maxillary sinus, the connected area of ethmoid sinus and the sphenoid sinus. (4) Total nasal cavity resistance was decreased after ESS. (5) After ESS airflow exchange increased in the nasal sinuses, most markedly in the maxillary sinus.</p><p><b>CONCLUSIONS</b>After ESS airflow velocity, flux and trace were altered. Airflow exchange increased in each nasal sinus, especially in the maxillary sinus.</p>

Influence of uncinate process on aerodynamic characteristics of nasal cavity and maxillary sinus / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>This study aimed to investigate the influence of uncinate process on air flow velocity, trace, distribution, air pressure, as well as the air flow exchange of nasal cavity and paranasal sinuses.</p><p><b>METHODS</b>Fluent software was used to simulate two nasal cavity and paranasal sinus structures following CT scanning, one had normal nasal cavity, the another had the nasal cavity with uncinate process removed. Air flow velocity, pressure, distribution and trace lines were calculated and compared by Navier-Stokes equation and numerically visualized between two models.</p><p><b>RESULTS</b>Air flow of two models in the common and middle meatus accounted for more than 50% and 30% of total nasal cavity flow. Flow velocity of two models were maximal in the common meatus, followed by the middle meatus. The maximal velocity existed on the left nasal district between limen nasi and head of inferior turbinate. The flow traces of two models were similar. In the normal model, the air flow velocity of the district around uncinate process was almost the same in inhale and exhale. In the model with the uncinate process removed, the air flow velocity of the district around uncinate process was faster, the air flow velocity in expiratory phase was quicker. Compared with the normal nasal cavity, there was more exchange of maxillary sinus in the model with cut uncinate process.</p><p><b>CONCLUSIONS</b>In the view of flow dynamics, the uncinate process effects the air flow velocity of the district around uncinate process and the exchange of maxillary sinus, the contribution of nasal flow is connected with the morphosis of the uncinate process.</p>