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.

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>

Effect of tympanic membrane perforation on vibration of hearing system / 医用生物力学

Objective To study the effects of the size and diffraction of tympanic membrane perforation on hearing system of human ear. Method The whole temporal bone from a healthy volunteer is scanned using spiral CT. The digitized outlines of images are imported into ANSYS to construct a three dimensional finite element model of the human ear. ResultsThe resonance frequencies become 3.6, 4.4 and 4.6 kHz with the increase of perforation areas as 0.97, 3.66 and 7.97 mm2, respectively. The larger perforation in the tympanic membrane results in a lower stapes footplate displacement. The displacement swing of the stapes footplate decreased clearly under the action of sound wave from the diffraction. The peak values of the displacement nephogram of the tympanic membrane are 0.32, 0.20 and 0.19 μm at 1000 Hz, respectively. At the resonance frequency, the peak values of the displacement nephogram of the tympanic membrane are 0.20, 0.14 and 0.09 μm, respectively. Conclusions The larger the size of the perforation is, the smaller stapes footplate displacement will be, especially at the lower frequency of 4 kHz with the higher resonance frequency. The peak values of displacement nephogram will become smaller with the increased size of perforations. The results would give helpful information for the clinical treatment.

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.