鼻腔-鼻窦间一氧化氮扩散状况的数值模拟研究

Numerical simulation of diffusion of nitric oxide between nasal airway and sinus cavity

关键词:  鼻  生物力学模型  气流场  NO

Key words:  [Key words]　nose  biomechanical model  airflow-field  nitric oxide

摘要:

[摘要]　目的　研究鼻腔-鼻窦气流场特征及一氧化氮(NO)在鼻腔-鼻窦间的分布与扩散状况。　方法　对1例真菌性鼻-鼻窦炎患者进行CT检查获取二维结构数据，进行三维重建，设定相应边界条件后，数值模拟潮气量为600 mL时鼻腔-鼻窦内的气流场；以此为基础进一步建立鼻腔气道简化数值模型，研究NO在鼻腔-鼻窦间的扩散过程以及上颌窦口NO质量分数、上颌窦口大小、中鼻道流速3个参数对NO扩散的影响。 　结果　（1）鼻腔气流场特征：气流量患侧为220 mL，健侧为380 mL；双侧气流分布特征相同，鼻阈区气流速度最快，气流主要经过总鼻道中、下部且流速较快，中鼻道、下鼻道、嗅裂气流分布较少且流速慢；鼻腔气流以层流为主，多个部位可观察到漩涡或反向气流。（2）上颌窦口局部气流场特征：呼气相和吸气相双侧上颌窦腔内流速均近乎为0 m/s；患侧上颌窦口与毗邻中鼻道几乎无压强差和流速差；而健侧则有一定的压强差和流速差，吸气相和呼气相压强差分别为6 Pa和2 Pa。（3）呼气相峰值时刻：上颌窦口NO质量分数分别为1和0.5时，前鼻孔与窦口处浓度比均为22%；上颌窦口直径分别为10 mm、7 mm时，上述质量分数比分别为27.5%、21%；当上颌窦口处流速分别为0.062 m/s、0.4 m/s时，上述质量分数比分别为27.5%、52.5%。　结论　上颌窦内气流以自由扩散方式运动，速度近乎为0 m/s；呼气相前鼻孔处NO质量分数与上颌窦口大小、窦口处NO质量分数及中鼻道流速呈正相关，但非线性关系。

Abstract:

[Abstract]　Objective　To analyze the airflow-field characteristics of nasal airway and the distribution of nitric oxide(NO) between nasal cavity and sinus cavity by numerical simulation.　Methods　Numerical simulation was performed on a patient of fungal rihinosinusitis (FRS), who received CT scan to achieve structured data and 3-D reconstruction. Nasal cavity and sinus cavity throughout the human nasal cavity during inspiration tidal volume was 600 mL. A simplified nasal airway model was reconstructed to analyze the diffusion process of nitric oxide between nasal cavity and sinus cavity and analyze the relation between NO mass fraction、the size of sinus、the velocity of middle nasal meatus and the diffusion of NO.　Results　 (1) The airflow field features of nasal cavity：air-flow of disease side 220 mL, air-flow of normal side 380 mL. The air flow distribution of two sides was similar; the airflow velocity was the fastest in nasal region. The nasal air-flow of FRS was mainly distributed in middle, lower of total nasal meatus and the velocity was faster. Middle,lower nasal meatus and the olfactory cleft region had the less air-flow and the velocity was slow; the most air-flow was laminar flow, vortex or re verse. (2) The airflow field features of ostium of maxillary sinus：in the stable state of breathing, bilateral maxillary sinus airflow velocity was almost zero; the pressure and speed of the maxillary sinus in the disease side were as same as the middle meatus, but the normal side had small difference, the pressure difference was 6 Pa and 2 Pa on the inspiratory phase and the expiration phase. (3) In the stable state of expiratory, the mass fraction of NO in sinus was 1, the highest concentration of NO in naris and sinus concentration ratio were 22%; when the concentration was 0.5, the ratio was 22%; the diameter in sinus was 10mm, the ratio was 27.5%; when the diameter was 7 mm, the ratio was 21%; the velocity of in sinus was 0.062 m/s, the concentration was 27.5%, when the velocity was 0.4 m/s, the ratio was 52.5%.　Conclusion　In the stable state of breathing, the gases produced in the maxillary sinus release in the manner of free diffusion. Maxillary sinus ai1rflow velocity is almost zero. The mass fraction of NO at the outlet of the nasal cavity are positively correlated to the size, concentration, velocity of sinus ostium，but non-linear relationship.