中文摘要：

目的人体由站姿或坐姿变为睡眠时的卧姿时,流体受重力的影响自腿部向头颈部迁移,导致气道周围软组织体积增加,压强增大,从而挤压气道,导致睡眠过程中气道更易阻塞。本研究针对阻塞性睡眠呼吸暂停（obstructive sleep apnea,OSA）患者,分析流体迁移对上气道截面形状以及气道流动阻力的影响。方法使用磁共振三维容积扫描方法,对受试者进行两种状态下的头颈部横断面成像：平卧参考状态以及双腿抬起持续8 min流体重新分布状态。从选定横断面的图像上分析这两种状态下气道截面积以及形状的改变,并从水力学半径的角度分析不同类型的形变对气道流动阻力的影响。结果相比于平卧参考状态时的气道截面形状,抬腿8 min流体重新分布后气道截面积改变的同时,形状呈现出三种类型变化：气道截面形状基本不变;气道截面长短轴比例变大,截面形状趋于更扁;气道截面长短轴比例变小,截面形状趋向圆形。这些不同形式的形状改变,可以对气道的阻力产生很大的影响。结论体位改变引起的流体迁移除了改变气道截面积之外,还会改变气道的截面形状,而截面形状的改变可对流动阻力产生重要影响。这一研究为深入探索OSA发生的机制提供了研究基础。

英文摘要：

ObjectiveWhen body posture changes from standing or sitting to a recumbent posture atbedtime,fluid displaces from the lower body into the neck due to gravity,which may increase the volume of thesoft tissues surrounding the upper airway and tissue pressure. As a result,it may narrow the upper airway andincrease the propensity of airway obstruction in patients with obstructive sleep apnea（OSA）. The aim of thisstudy is to analyze the effects of fluid shift on the shape of the airway cross section and flow resistance.Method Using three-dimensional spoiled gradient echo sequence,we perform magnetic resonance imaging（ MRI） for OSAsubjects under two conditions：with subjects lying supine（the control）, and elevating both legs for 8 min, whichcauses fluid redistribution. We analyze the changes in thecross-sectional area and shape of the upper airway usingselected axial images,and evaluate the effects of differentshape changes on the airway resistance based on hydraulicradius theory.ResultsCompared to the control stage,there are three types of shape changes in the cross-sectionof the upper airway after leg raising for 8 min：the shape basically remains unchanged;the ratio of the major tominor axis increases,which means that the shape becomes more elliptical;and the ratio of the major to minoraxis decreases,which means that the shape becomes more circular. The changes in the cross-sectional shapehave significant effects on the flow resistance.ConclusionsFluid shift induced by posture change can changenot only the cross-sectional area,but also the shape of the upper airway. The change in shape has significanteffects on flow resistance. This study provides an important basis for further investigations on OSA mechanism.