Pilot study of pressure-flow properties in a numerical model of the middle ear.

Background: Constructing a three-dimensional (3D) model through non-invasive techniques will greatly benefit the diagnosis and treatment of otitis media. However, such a model should reflect the physiological characteristics of the middle ear; in particular, the pressure-flow responses determine the validity of the model. Objectives: A 3D model of the middle ear was constructed by digital scanning and simulation. The pressure-flow properties in the model were measured to evaluate whether the model could reflect the real middle ear under physiological and pathological conditions. Materials and methods: Computed tomography (CT) scanning data from a healthy woman were input into Mimics 20.0 to construct 3D images of the middle ear. The 3D images were treated with Ansys 15.0 for finite element mesh generation. Msc Nastran 2014 were used for the fluid-solid coupling calculations. Results: The pressure-flow rate in the model resembled a Venturi tube, namely, the pressure decreased with increasing flow velocity, especially in the Eustachian tube. In the absence of the right mastoid process, the differences in air pressure and the maximal velocity in the model were reduced. Conclusions: This numerical model based on CT images of the middle ear recapitulates the biomechanical characteristics of the real middle ear. Significance: This study provides an easy and rapid approach to constructing a middle ear model for diagnosis and treatment of otitis media.

Numerical analysis of the relationship between nasal structure and its function.

The functions of the nasal cavity are closely related to its structure. In this study the three-dimensional finite element models were established based on the clinical data of twenty-four volunteers to study the influence of nasal structure on nasal functions of heating the inhaled airflow. Numerical simulations mainly concerning the airflow distribution and the airflow temperature are performed. The character of airflow heating process in these models is gained from the simulation results of these nasal cavities. The parameters describing the geometry of nasal cavity, such as the surface area of nasal airway and the volume of nasal cavity, are considered to be related to the nasal function of heating the inhaled airflow. The approximate function describing the relationship between the geometric parameters of the nasal airway and the nasal functions is gotten. This study can provide a numerical platform for studying some clinical problems and will contribute to the further research on the relationship between nasal structure and nasal functions.

[Nasal cavity computer fluid dynamics analysis on 60 healthy Chinese adults].

OBJECTIVES: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

[Effect of septoplasty or in combination with out fracture of the inferior turbinate on the airflow field and nasal airway].

OBJECTIVE: 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. METHODS: 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. RESULTS: 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). CONCLUSION: 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.

Increased expression of granulocyte colony-stimulating factor mediates mesenchymal stem cells recruitment after vascular injury.

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

[Analysis of the character of self-adaptation of nasal structure in patients with nasal septum deviation].

OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

[Structure of nasal cavity and characters of airflow].

OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.