中文摘要：

目的当人体由站姿或坐姿改变为卧姿时，下肢流体会向头颈部迁移，导致上气道变窄，从而引起或加重睡眠呼吸障碍。本研究提出一种用力学模型与有限元分析手段研究流体迁移引起的气道形态改变的方法，从而可以进行头颈部流体增加量与气道横截面积以及皮肤周长改变之间定量关系的研究。方法借助于人体头颈部气道最狭窄部位的轴状面磁共振图像，构建基于真实解剖结构的二维力学与有限元分析模型。通过均匀增加软组织面积来模拟头颈部组织流体量的增加，用模型预测其对气道截面尺度的影响。结果根据2名健康男性头颈部解剖结构建立相应的有限元模型。通过模型模拟结果与实验数据的对比，验证了此模型方法用来模拟与预测流体迁移影响的合理性。模型结果验证了头颈部流体的增加会对气道横截面积产生影响的实验观察。模拟结果显示，随着截面内流体量的增多，气道横截面积逐渐减小，皮肤周长逐渐增大。气道面积的变化与流体量的变化呈非线性关系。结论有限元模型的方法可以在流体迁移影响研究中扮演重要角色。模型初步预测结果表明，当伴有水肿现象的疾病，例如心力衰竭、肾衰竭等，导致夜间有更多流体进入患者头部时，会加重气道变窄程度，使其更易发生阻塞，导致阻塞性睡眠呼吸暂停症状的加剧。

英文摘要：

Objective When the body posture changed from a standing or sitting posture to a recumbent posture, fluid in the lower body would shift into the head and neck, which could make upper airway narrow and thus cause or aggravate sleep disorders. This study employed a mechanical model and finite element analysis to investigate airway patency. This method could then be used to study the quantitative relationships between the changes in the cross-sectional area of the upper airway, or skin circumference, and the amount of the fluid accumulation in head and neck tissues. Methods We developed two-dimensional mechanical and finite elementmodels with realistic anatomical structures based on magnetic resonance images on an axial plane of the head and neck, which had the narrowest cross-sectional area of the upper airway. We simulated the increase in the amount of fluid in the head and neck by uniformlyincreasing the cross-sectional area of the soft tissues, and predicted its effect on upper airway size. Results We built finite element models for two healthy males based on their anatomical structures. By comparing model- predicted results with measured data, we validated the soundness of simulating and predicting the effects of fluid shift using such a modeling method. The model-predicted results confirmed the experimental observation that an increase in the amount of fluid in the head and neck could affect the cross-sectional area of the upper airway. The model-predicted results showed that with an increase in the amount of fluid, the cross-sectional area of the upper airway decreased and the skin circumference increased on the selected plane. The models also predicted that the relationship between the changes in the cross-sectional area of the upper airway and the amount of fluid was nonlinear. Conclusions The finite element models could play an important role in studying the effects of fluid shift. The preliminary model-predicted results showed that shifting more fluid into the head and neck during sleep could worsen the na