Krieger J, Petiau C, Sforza E, Weiss T, Thibault A, Bazin A
Service d'explorations fonctionnelles du système nerveux et de pathologie du sommeil, hôpitaux universitaires de Strasbourg, France.
Neurophysiol Clin. 1998 Dec;28(6):493-506. doi: 10.1016/s0987-7053(99)80018-5.
The upper airway can be described as a collapsible segment (the pharynx) interposed between two rigid bony (the cavum) or cartilaginous (the trachea) segments. Due to this structure, the pharynx behaves as a collapsible tube, in which airflow does not depend on the downstream pressure, but is limited to a maximum value which depends only on the upstream pressure and on the pressure surrounding the collapsible segment; this behavior, known as a Starling resistor can be modeled by the waterfall effect. Thus, the upper airways can be in three different conditions: an occluded condition, in which no flow is possible, a patent condition, in which flow depends on the difference between upstream and downstream pressures (according to Poiseuille's law), and a situation in which flow is limited. The behavior of the upper airway is largely dependent on its anatomic structure, but functional factors play a critical role. Among these sleep state is both a determinant of the collapsibility of the pharynx, and determined by the simulation of upper airway mechanoreceptors whose activity depends on the activity of respiratory muscles. Thus the interplay of three factors: ventilatory drive, upper airway collapsibility, and arousal threshold can predict most of the situations of stable and unstable ventilatory behavior during sleep. The level of the arousal threshold governs the stability of the ventilatory pattern, as it determines whether a combination of slow, respiratory effort, and blood gases can be maintained or is interrupted by an arousal.
上气道可被描述为介于两个刚性骨段（鼻腔）或软骨段（气管）之间的一个可塌陷节段（咽）。由于这种结构，咽表现为一个可塌陷的管道，其中气流不取决于下游压力，而是限于一个仅取决于上游压力和可塌陷节段周围压力的最大值；这种行为，即所谓的斯塔林电阻器，可用瀑布效应来模拟。因此，上气道可处于三种不同状态：阻塞状态，即无气流通过；开放状态，即气流取决于上下游压力差（根据泊肃叶定律）；以及气流受限状态。上气道的行为很大程度上取决于其解剖结构，但功能因素也起着关键作用。其中，睡眠状态既是咽部可塌陷性的决定因素，又由上气道机械感受器的模拟所决定，而上气道机械感受器的活动取决于呼吸肌的活动。因此，通气驱动、上气道可塌陷性和觉醒阈值这三个因素的相互作用可以预测睡眠期间大多数稳定和不稳定通气行为的情况。觉醒阈值的水平决定了通气模式的稳定性，因为它决定了缓慢呼吸努力和血气的组合是能够维持还是会被一次觉醒打断。
