The mechanism of sensing postural changes in human ears by numerical simulation / 医用生物力学

Objective To study the general mechanical behavior pattern of sensing angular velocity by 3 pairs of human semicircular canals. Methods Sinusoidal head rotation of a healthy subject was simulated by finite element method to analyze the dynamic responses in the above 3 pairs of canals in the left and right inner ear. Results Compared with the complicated node displacement distribution, the volumetric strain distribution of cupula was regular. Specifically, each pair of cupulae expanded or contracted within the same amplitude with the same response frequency to the angular velocity. The ratio of absolute volumetric strain among the horizontal semicircular canal cupula (HC cupula), the anterior semicircular canal cupula (AC cupula), and the posterior semicircular canal cupula (PC cupula), was approximately 1.00︰0.80︰1.72, which kept constant. In addition, the volumetric strain of HC cupula was in phase with that of AC cupula, but showing 14.4° out of phase with the angular velocity, and 180° out of phase with that of PC cupula. Conclusions The volumetric strain of cupula can preferably characterize the directional coding function of semicircular canal, and the amplitude, frequency and phase of the cupular volumetric strain can encode those of the stimulated angular velocity, respectively. These results will lay the foundation for establishing quantitative relationship of vestibulo-ocular reflex, and provide theoretical references for quantitative assessment for vestibular function by nystagmus examination.

The mechanism of sensing postural changes in human ears by numerical simulation / 医用生物力学

Objective To study the general mechanical behavior pattern of sensing angular velocity by 3 pairs of human semicircular canals.Methods Sinusoidal head rotation of a healthy subject was simulated by finite element method to analyze the dynamic responses in the above 3 pairs of canals in the left and right inner ear.Results Compared with the complicated node displacement distribution,the volumetric strain distribution of cupula was regular.Specifically,each pair of cupulae expanded or contracted within the same amplitude with the same response frequency to the angular velocity.The ratio of absolute volumetric strain among the horizontal semicircular canal cupula (HC cupula),the anterior semicircular canal cupula (AC cupula),and the posterior semicircular canal cupula (PC cupula),was approximately 1.00∶0.80 ∶ 1.72,which kept constant.In addition,the volumetric strain of HC cupula was in phase with that of AC cupula,but showing 14.4° out of phase with the angular velocity,and 180° out of phase with that of PC cupula.Conclusions The volumetric strain of cupula can preferably characterize the directional coding function of semicircular canal,and the amplitude,frequency and phase of the cupular volumetric strain can encode those of the stimulated angular velocity,respectively.These results will lay the foundation for establishing quantitative relationship of vestibulo-ocular reflex,and provide theoretical references for quantitative assessment for vestibular function by nystagmus examination.

The mechanism of sensing postural changes in human ears by numerical simulation / 医用生物力学

Objective To study the general mechanical behavior pattern of sensing angular velocity by 3 pairs of human semicircular canals.Methods Sinusoidal head rotation of a healthy subject was simulated by finite element method to analyze the dynamic responses in the above 3 pairs of canals in the left and right inner ear.Results Compared with the complicated node displacement distribution,the volumetric strain distribution of cupula was regular.Specifically,each pair of cupulae expanded or contracted within the same amplitude with the same response frequency to the angular velocity.The ratio of absolute volumetric strain among the horizontal semicircular canal cupula (HC cupula),the anterior semicircular canal cupula (AC cupula),and the posterior semicircular canal cupula (PC cupula),was approximately 1.00∶0.80 ∶ 1.72,which kept constant.In addition,the volumetric strain of HC cupula was in phase with that of AC cupula,but showing 14.4° out of phase with the angular velocity,and 180° out of phase with that of PC cupula.Conclusions The volumetric strain of cupula can preferably characterize the directional coding function of semicircular canal,and the amplitude,frequency and phase of the cupular volumetric strain can encode those of the stimulated angular velocity,respectively.These results will lay the foundation for establishing quantitative relationship of vestibulo-ocular reflex,and provide theoretical references for quantitative assessment for vestibular function by nystagmus examination.

Numerical analysis on deposition of particulate matters in respiratory tract / 医用生物力学

Objective To study the regular pattern of inhalational particulate matter deposition in respiratory tract and its influencing factors during breathing by numerical simulation method. Methods Three-dimensional finite element model of normal human respiratory tract was established to simulate the airflow distributions in respiratory tract during inspiration. The particles were released at the entrance of nose or mouth to simulate the deposition process of suspended particles by inhaled airflow in respiratory tract. Different parameters such as particle diameter, particle density and flow rate of air volume were used for comparative analysis to investigate their functions as influencing factors when particle deposition happened in respiratory tract. Results The particles were mainly deposited in nasal threshold, nasal middle airway, nasopharynx, and bronchial inner wall of respiratory tract. The particle deposition rate increased with the parameters of particle diameter, particle density and air volume flow rate increasing. The influence of different parameters on the deposition rate was not the same. Conclusions The particle is mainly deposited at the site with complex geometry or at the position where path direction changes violently. Particle diameter, density and breathing airflow rate will affect the deposition rate in respiratory tract. These research findings will provide numerical references for the clinical assessment on risk of respiratory diseases caused by air pollution.

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.

Nasal cavity computer fluid dynamics analysis on 60 healthy Chinese adults / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVES</b>To investigate the aerodynamics characteristics of nasal cavity in inspiration phase from 60 healthy Chinese people and provide the reference values for future computational fluid dynamics (CFD) research.</p><p><b>METHODS</b>CFD was used for numerical simulation. The indices of main airflow passage, total nasal airway resistance, maximal velocity, maximal wall shear stress, nasal mucosa area, nasal volume and surface area-to-volume ratio were extracted from CFD analysis results. SPSS 16.0 software was used to analyze the data.</p><p><b>RESULTS</b>The main airflow passage in nasal cavity was common meatus, the mean total nasal airway resistance was (0.211 ± 0.085) kPa·s·L(-1), the mean maximal velocity was (12.01 ± 2.79) m/s, the mean maximal wall shear stress was (2.50 ± 0.89) Pa, the mean nasal mucosa area was (161.2 ± 34.7) mm(2), the mean nasal volume was (31.7 ± 8.1) ml and the mean surface area-to-volume ratio was (0.58 ± 0.09) mm(-1). No significant difference was detected in aerodynamics indices between male and female people.</p><p><b>CONCLUSIONS</b>The main airflow passage is located in common meatus. The nasal valve area is the key constrictive plane in nasal cavity. There are no gender differences of main airflow characteristics in nasal cavity. The normal ranges of aerodynamics indices could be used for reference values for future CFD research.</p>

Increased expression of granulocyte colony-stimulating factor mediates mesenchymal stem cells recruitment after vascular injury / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Recent studies indicate that bone marrow-derived cells may significantly contribute to atherosclerosis, post-angioplasty restenosis and transplantation-associated vasculopathy. The responsible bone marrow (BM) cells and mechanisms regulating the mobilization of these cells are currently unclear. The purpose of this study was to investigate the expression of granulocyte colony-stimulating factor (G-CSF) on injured arteries and its effects on mesenchymal stem cells (MSCs) differentiation into vascular smooth muscle cells (VSMCs) in the process of vascular remodeling.</p><p><b>METHODS</b>Balloon-mediated vascular injury was established in female rats (n = 100) which received radioprotective whole female BM cells by tail vein injection and male MSCs through a tibial BM injection after lethal irradiation. The injured and contralateral carotid arteries were harvested at 3, 7, 14 and 28 days after treatment.</p><p><b>RESULTS</b>Morphometric analysis indicated that intima to media area-ratio (I/M ratio) significantly increased at 28 days, 0.899 ± 0.057 (P < 0.01), compared with uninjured arteries. Combining fluorescence in situ hybridization (FISH) and immunohistochemical analysis showed that a significant number of the neointimal cells derived from MSCs, (45.2 ± 8.5)% at 28 days (P = 0.01), compared with (23.5 ± 6.3)% at 14 days. G-CSF was induced in carotid arteries subject to balloon angioplasty (fold mRNA change = 8.67 ± 0.63 at three days, relative G-CSF protein = 0.657 ± 0.011 at three days, P < 0.01, respectively, compared with uninjured arteries). G-CSF was chemotactic for MSCs but did not affect the differentiation of MSCs into smooth-muscle-like cells.</p><p><b>CONCLUSION</b>Increased expression of G-CSF by injured arteries plays an essential role in contribution to recruitment and homing of MSCs to the site of the arterial lesion.</p>

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.

Advances on biomechanical model of human upper airway / 医用生物力学

Rebuilding the biomechanical model of human upper airway is an effective method for studying upper airway structure of human and its function, and it is also helpful to predict and make the treatment for upper airway diseases. This paper summarized the advances on biomechanical model of human upper airway and its application in clinical treatment, as well as try to make prediction about the research work in the future.

Numerical analysis of the nasal cavity structure reconstruction effects on the airflow patterns within the upper airway in patient with OSAHS / 医用生物力学

Objective To investigate the influence of airway structural changes after reconstruction of nasal cavity structure on the airflow patterns within the whole upper airway and the movement of soft palate in patient with OSAHS accompanied by nasal abnormality. Method Based on the preoperative and postoperative CT data from the patient with OSAHS, the three dimensional finite element model of the upper airway and the soft palate were reconstructed. The preoperative and postoperative flow characteristics of the upper airway and movement of the soft palate were simulated by the fluid solid interaction method. Results The surgical operation altered the abnormal anatomy of the nasal cavity. The nasal airway resistance and the whole upper airway resistance decreased significantly. Meanwhile, it was shown that the soft palate edema remitted obviously, and the motion amplitude of the free edge also decreased. The displacement of the soft palate increased with the decrease in elastic modulus of soft palate. Postoperative numerical results showed a good agreement with the experimental and computational results of the normal human in literature review. Conclusions The reconstruction of the nasal cavity structure influenced the airflow patterns and the movement of soft palate through altering the anatomy of the upper airway. The movement of soft palate was affected by the variations of elastic modulus under different pathophysiologic conditions.

Internal boundary parameters identification of human middle ear with neural network / 医用生物力学

Objective To study the method of internal boundary parameters identification of middle ear.Method The numerical model is created using CT technology.Based on Matlab tools,the neural network for identifying internal boundary is proposed.Result The uniform pressure of 105 dB is applied at the outside of the tympanic membrane,and the harmonic analysis is calculated on the model to take the training samples.The internal condition parameters are identified using the good neural network.Conclusions The investiga-tion shows that the inverse method reveals a fast convergence and a high degree of accuracy.

Internal boundary parameters identification of human middle ear with neural network / 医用生物力学

Objective To study the method of internal boundary parameters identification of middle ear.Method The numerical model is created using CT technology.Based on Matlab tools,the neural network for identifying internal boundary is proposed.Result The uniform pressure of 105 dB is applied at the outside of the tympanic membrane,and the harmonic analysis is calculated on the model to take the training samples.The internal condition parameters are identified using the good neural network.Conclusions The investiga-tion shows that the inverse method reveals a fast convergence and a high degree of accuracy.

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>

Determination of 13 Kinds of Aldehyde and Ketone Pollutants of Indoor Air by HPLC at One Time / 环境与健康杂志

Objective To establish a method for determination of 13 kinds of aldehyde and ketone pollutants in indoor air by HPLC at one time. Methods The aldehyde and ketone compounds in the air react with 2 4-DNPH and form hydrazone derivatives then determined by HPLC with SPD detection at a flow of CH3CN∶H2O 70∶30 365 nm wavelength. Results 13 kinds of hydrazone were favorably separated the average recovery rates were 96%～101% the lowest detection limits were 0.002～0.02 mg/m3 the linearity range was 0.1～4.0 mg/m3. Conclusion This method can be used for quantitative analysis of 13 kinds of aldehyde or ketone pollutants in indoor air at one time.