Bates J H, Decramer M, Chartrand D, Zin W A, Boddener A, Milic-Emili J
J Appl Physiol (1985). 1985 Sep;59(3):732-7. doi: 10.1152/jappl.1985.59.3.732.
Airway opening pressure, esophageal pressure, and flow were obtained during relaxed expirations in two normal anesthetized paralyzed dogs. The signal-to-noise ratio in the flow signals was greatly increased by averaging 10 different signals obtained with the same lung inflation volume. Numerical integration of an averaged flow signal then yielded the time course of the volume of the respiratory system above functional residual capacity (the elastic equilibrium volume). Comparison of volume signals obtained with different inflation volumes suggests that the resistance of the respiratory system increases with flow. The flow-volume and semilog volume curves show that expiration is induced by two apparently separate mechanisms: one causes emptying of most of the expired volume over a time interval of much less than 1 s, whereas the other contributes a relatively small amount to the expired volume over a significantly longer time (greater than or equal to 1 s). We postulate the first mechanism to be due to that of the respiratory system behaving like a single unit, with an elastance that is slightly volume dependent, emptying through a single airway which has a resistance that increases with flow. From the nature of airway opening pressure and esophageal pressure measured after occlusion in midexpiration, we conclude that the second mechanism is due to the viscoelastic properties (i.e., creep) of the respiratory system. The properties are manifest mainly in the chest wall.
在两只正常麻醉且瘫痪的犬类动物中，于呼气放松阶段获取气道开口压力、食管压力和气流数据。通过对相同肺充气量下获取的10个不同气流信号进行平均处理，气流信号的信噪比大幅提高。对平均气流信号进行数值积分，进而得出呼吸系统高于功能残气量（弹性平衡容积）的容积随时间变化的过程。比较不同充气量下获得的容积信号表明，呼吸系统的阻力随气流增加。流量 - 容积曲线和半对数容积曲线显示，呼气由两种明显不同的机制引发：一种机制在不到1秒的时间间隔内使大部分呼出容积排空，而另一种机制在显著更长的时间（大于或等于1秒）内对呼出容积的贡献相对较小。我们推测第一种机制是由于呼吸系统表现得如同一个单一单元，其弹性略微依赖于容积，通过一条阻力随气流增加的单一气道排空。从中期呼气阻塞后测量的气道开口压力和食管压力的性质来看，我们得出第二种机制是由于呼吸系统的粘弹性特性（即蠕变）。这些特性主要在胸壁中表现出来。
