Fouke J M, Strohl K P
J Appl Physiol (1985). 1987 Jul;63(1):375-80. doi: 10.1152/jappl.1987.63.1.375.
The occurrence of upper airway obstruction during sleep and with anesthesia suggests the possibility that upper airway size might be compromised by the gravitational effects of the supine position. We used an acoustic reflection technique to image airway geometry and made 180 estimates of effective cross-sectional area as a function of distance along the airway in 10 healthy volunteers while they were supine and also while they were seated upright. We calculated z-scores along the airway and found that pharyngeal cross-sectional area was smaller in the supine than in the upright position in 9 of the 10 subjects. For all subjects, pharyngeal cross-sectional area was 23 +/- 8% smaller in the supine than in the upright position (P less than or equal to 0.05), whereas glottic and tracheal areas were not significantly altered. Because changing from the upright to the supine position causes a decrease in functional residual capacity (FRC), six of these subjects were placed in an Emerson cuirass, which was evacuated producing a positive transrespiratory pressure so as to restore end-expiratory lung volume to that seen before the position change. In the supine posture an increase in end-expiratory lung volume did not change the cross-sectional area at any point along the airway. We conclude that pharyngeal cross-sectional area decreases as a result of a change from the upright to the supine position and that the mechanism of this change is independent of the change in FRC.
睡眠期间以及麻醉状态下出现上呼吸道梗阻表明，仰卧位的重力作用可能会使上呼吸道尺寸减小。我们使用声学反射技术对气道几何形状进行成像，并在10名健康志愿者仰卧位和直立位时，沿着气道长度每隔一段距离对有效横截面积进行了180次估算。我们计算了沿气道的z分数，发现10名受试者中有9名仰卧位时的咽部横截面积小于直立位时。对于所有受试者，仰卧位时咽部横截面积比直立位时小23±8%（P≤0.05），而声门和气管面积无显著变化。由于从直立位变为仰卧位会导致功能残气量（FRC）减少，其中6名受试者被置于爱默生胸甲中，通过抽空胸甲产生正跨呼吸压，以便将呼气末肺容积恢复到体位改变前的水平。在仰卧位时，呼气末肺容积增加并未改变气道沿线任何位置的横截面积。我们得出结论，从直立位变为仰卧位会导致咽部横截面积减小，且这种变化机制与FRC的变化无关。
