Numerical study on biomechanical model of the upper airway and part of bronchus / 医用生物力学

Objective To establish the biomechanical model of the upper airway, trachea and part of bronchus, and study the influences of different breathing modes on flow characteristics and airway resistance. Methods Based on data of CT scans, three-dimensional finite element model of an anatomically accurate upper airway was established, including the nasal cavity, oral cavity, pharynx, larynx, trachea and part of bronchus. According to several typical cases in reality, numerical simulations were performed on airflow characteristics in upper airway with different proportion of oral airflow and nasal airflow. Results When only a small amount of airflow was inhaled from the mouth, the distribution of airflow characteristics and the airway resistance were similar to the case of nasal inhalation. When a large amount of airflow was inhaled or exhaled through the mouth, the distribution of airflow, pressure and shear stress changed significantly in the respiratory tract. The main differences were observed in the nasal cavity and the oral cavity. Conclusions Establishing the biomechanical model of the upper airway, trachea and part of bronchus is helpful to understand airflow distributions in the entire upper airway and part of bronchus during respiration and to build the platform of numerical research on pathogenesis of upper airway structure-related diseases.

Effect of septoplasty or in combination with out fracture of the inferior turbinate on the airflow field and nasal airway / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To explore the effect of septoplasty or in combination with out fracture of the inferior turbinate in patients with nasal septum deviation on the airflow field and the nasal airway structure.</p><p><b>METHODS</b>Six patients with nasal septum deviation underwent spiral CT imaging scans before surgery and during the follow-up. The 3D finite element meshes of the nasal airway were developed from the above CT scans. Given three preconditions, the nasal airflow fields were described by the Navier-Stokes and continuity equations at the inspiratory flow rate of 12 L/min. The whole airflow patterns were obtained and then compared with the airflow filed and airway structure changes before and after surgery. SPSS 12.0 software was used to analyze the data.</p><p><b>RESULTS</b>Before surgery, area of the common airway and the middle and ventral medial regions in the concave side were (1.61 ± 0.18), (0.40 ± 0.10), (0.40 ± 0.14) cm(2) respectively, and those of convex side were (1.30 ± 0.18), (0.33 ± 0.05), (0.36 ± 0.10) cm(2) respectively. The differences between both sides were of no statistical significance (Z value was 1.782, 1.363, 0.526 respectively, all P > 0.05). Airflow of the above airways were (361 ± 68), (131 ± 25), (100 ± 28) ml respectively in concave side and (178 ± 33), (59 ± 26), (59 ± 18) ml respectively in convex side, which differences were significant statistically (Z value were 2.207, 2.201, 2.201 respectively, all P < 0.05). The inferior turbinate in concave side [(0.93 ± 0.10) cm] was statistically (Z = 2.214, P < 0.05) bigger than that in convex side [(0.58 ± 0.12) cm] before surgery. The airflow fields were in disorder in both ill-airways. After surgery, area of the common airway was (2.55 ± 0.44) cm(2) in concave side and (2.20 ± 0.72) cm(2) in convex side respectively, and area of the middle and ventral medial regions in the convex side were (0.58 ± 0.13), (0.81 ± 0.26) cm(2) respectively, which differences were of significance statistically when comparing to areas before surgery (Z value were 2.201, 2.201, 2.201, 2.201, P < 0.05). The airflow passed through nasal airway orderly in both sides. But the thickness of inferior turbinate was (0.73 ± 0.08) cm in concave side after surgery, which difference was significant statistically in comparison to that before surgery (Z = 2.264, P < 0.05). Consequently, nasal resistance decreased from (0.41 ± 0.03) kPa×L(-1)×s(-1) to (0.16 ± 0.01) kPa×L(-1)×s(-1) after surgery, the difference was significantly (Z = -2.207, P = 0.027).</p><p><b>CONCLUSION</b>Septoplasty or in combination with out fracture of the inferior turbinate, followed by the self-adaptation consecutively, could improve the airway and breathing capacity of the nose.</p>

Numerical simulation for the influence of nasal cavity structure on nasal function of warming and humidifying the inhaled airflow / 医用生物力学

Objective To study the influence of nasal cavity structure on nasal function of warming and humidifying the inhaled airflow. Method Nine normal persons and two patients with deviation of nasal septum (pre and post operation) were selected as research subjects. The three dimensional finite element model of nasal cavities of these volunteers was established. Numerical simulations for the airflow distribution, the airflow temperature and the airflow humidity in the nasal cavity were performed. Based on the simulation results, comparisons were made between normal nasal cavities and the patient’s nasal cavities as well as between the pre-and post-operative nasal cavities. ResultsIn the wider side of nasal cavity, the volume flow rate and the velocity of airflow were higher and the effect of warming and humidifying on the airflow was worse. For normal people, the nasal cavity for warming and humidifying the inhaled airflow was in the anterior segment of the nose. While for the patients, the main segment of warming and humidifying the inhaled airflow had to depend on the airway geometry. Conclusions The nasal cavity structure can influence the effect of warming and humidifying on the airflow. The parameters describing the geometry of nasal cavity, such as the surface area of nasal airway and volume of nasal cavity, may be a useful measurement for the nasal function of warming and humidifying the inhaled airflow.

Analysis of the character of self-adaptation of nasal structure in patients with nasal septum deviation / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To analyze the different characters of nasal airflow-field between 10 patients with nasal septum deviation and 20 healthy Chinese people by the method of three-dimensional reconstruction of these people's nasal cavity and numerical simulation of the flow field in these nasal cavity models. The character of airflow-field was considered by analyzing the relationship between the structure and function of the human nose.</p><p><b>METHODS</b>Based on the data obtained from the CT images, 10 patients with nasal septum deviation and 20 healthy Chinese people's nasal cavity models were reconstructed by the method of surface rendering. The flow field in these three-dimensional models was simulated with finite element method. The different characters of nasal airflow-field was analysed between two groups of people.</p><p><b>RESULTS</b>The airflow distribution in the nasal cavity model could be acquired from the simulation results of the velocity. The airflow for patients with nasal septum deviation mainly passed through the broad nasal cavity, especially in the middle part of meatus of nose. In the healthy people group, the airflow mainly passed through the main side of the nasal cavity, especially in the middle and inferior part of the meatus of nose. The pressure value at any point in the nasal cavity model could be obtained from the results of the pressure plot. In the patients with nasal septum deviation, the pressure mainly dropped in the part of the nasal septum deviation, accounting approximately 71.36% of the total pressure drop. In the group of healthy people, the pressure dropped mainly in the limen nasi, accounting approximately 58.78% of the total pressure drop. The nasal airway resistance of the patients with nasal septum deviation was larger than that in the group of healthy people.</p><p><b>CONCLUSIONS</b>The three-dimensional nasal airway can reflect the characters of the human nasal airway. It can be used to analyze the change of the aerodynamic in nasal cavity caused by the abnormal anatomy of the nose. This experiment can proof that human nose has the function of self-adaptation, it can build a foundation for the construction of the model of self-adaptation of the human nose.</p>

Structure of nasal cavity and characters of airflow / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To study the airflow in nasal cavity by reconstructing 20 volunteers' nasal cavity models and numerical simulation of the flow field in these nasal cavity models.</p><p><b>METHODS</b>Based on the data from the CT images, 20 volunteers' nasal cavity models were reconstructed by the method of surface rendering. The flow field in these three-dimensional models were simulated with finite element method. Some of these volunteers were tested by means of acoustic rhinometry and the test results recorded. Comparisons were performed for the curves from acoustic rhinometry and the results of numerical simulations. The simulation results were explained with the fluid network theory.</p><p><b>RESULTS</b>The airflow distribution in the nasal cavity model could be acquired from the simulation results of the velocity plot. Main airflow would pass through the common nasal meatus in which flux accounted for 50% - 77% of overall flux. The pressure value at any point in the nasal cavity model could be obtained from the results of the pressure plot. The nasal airway resistance in the region of limen nasi accounted for 50% - 65% of overall nasal airway resistance. Comparing the test results with the simulation results the relation could be understood between the change of the cross-section area of nasal cavities and the plot of numerical simulation results of velocity and pressure in airflow field in the nasal cavity models.</p><p><b>CONCLUSIONS</b>Comparing the simulated results of the 20 volunteers' nasal cavity model it can be concluded that the distribution of airflow in nasal cavities is not stationary. The differences among everybody's nasal cavity structure lead to the different airflow distribution in the nasal cavities.</p>