Sasaki H, Hoppin F G
J Appl Physiol Respir Environ Exerc Physiol. 1979 Dec;47(6):1251-62. doi: 10.1152/jappl.1979.47.6.1251.
How does smooth muscle tone affect the properties of airways during breathing maneuvers? We have studied the dynamic relationships of airway pressure and cross-sectional area in excised dog lobes and isolated tracheal segments during simulated breathing maneuvers. When contracted by carbachol, airways developed complex hysteretic behavior, becoming less compliant in small tidal breaths and rapid deflations, and grossly hysteretic in large tidal maneuvers. For a given sequence of maneuvers the patterns of hysteresis varied with timing. Analogous behavior was seen during length-cycling of dog trachealis muscle strips. The mechanisms suggested by the hysteretic patterns of muscle length-tensional plots are 1) slipping of contractile filaments at threshold forces during lengthening and 2) active shortening of contractile filaments that is slow relative to many respiratory events. The observed behavior indicates that measurements of pulmonary function that depend on airway caliber or stiffness should become increasingly affected by the sequence, amplitude, and timing of breathing maneuvers as smooth muscle tone increases. The stiffness for small amplitude cycling may be favorable for local control of ventilation by parenchymal smooth muscle.
在呼吸动作过程中，平滑肌张力如何影响气道特性？我们研究了在模拟呼吸动作期间，切除的犬肺叶和离体气管节段中气道压力与横截面积之间的动态关系。当被卡巴胆碱收缩时，气道出现复杂的滞后行为，在小潮气量呼吸和快速呼气时顺应性降低，在大潮气量动作时出现明显的滞后现象。对于给定的动作序列，滞后模式随时间而变化。在犬气管肌条的长度循环过程中也观察到了类似行为。肌肉长度-张力图的滞后模式所提示的机制为：1）在延长过程中收缩丝在阈值力作用下滑动；2）收缩丝的主动缩短相对于许多呼吸事件而言较为缓慢。观察到的行为表明，随着平滑肌张力增加，依赖气道管径或硬度的肺功能测量结果将越来越受到呼吸动作序列、幅度和时间的影响。小幅度循环时的硬度可能有利于实质平滑肌对通气进行局部控制。
