Shardonofsky F R, Sato J, Bates J H
Meakins-Christie Laboratories, McGill University, Montreal, Quebec, Canada.
J Appl Physiol (1985). 1990 May;68(5):2230-6. doi: 10.1152/jappl.1990.68.5.2230.
We investigated the quasi-static pressure-volume (P-V) hysteresis of the normal canine lung in vivo by performing 15-s flow interruptions at various points throughout the breathing cycle in mechanically ventilated anesthetized paralyzed dogs. By measuring the transpulmonary pressure (Ptp) at 5 s after each interruption, we built up a quasi-static P-V loop of the lungs. We found, however, that the area of the loop was significantly smaller (by a factor of 4-6) than has been reported by others for the isolated canine lung. We also found the hysteresis loop area of the chest wall to be of similar magnitude. If we measured Ptp 10-15 s after interruption, we found it always decreased at a rate expected to result from continuing gas exchange in the lungs. We conclude that 1) the areas of the quasi-static P-V loop in vivo for the total respiratory system, as well as the lungs and chest wall separately, are significantly smaller than has been reported previously for isolated lungs and 2) continuing gas exchange in the lungs places a lower limit on the frequencies (equivalent to flow interruptions of greater than 5- to 7-s duration) at which the P-flow-V behavior of the lungs in vivo can be considered in purely mechanical terms.
我们通过在机械通气、麻醉、麻痹的犬类中，在整个呼吸周期的不同时间点进行15秒的气流中断，研究了正常犬类肺脏在体内的准静态压力-容积（P-V）滞后现象。通过测量每次中断后5秒时的跨肺压（Ptp），我们构建了肺脏的准静态P-V环。然而，我们发现该环的面积比其他人报道的离体犬肺的面积显著更小（缩小了4至6倍）。我们还发现胸壁的滞后环面积大小相似。如果我们在中断后10至15秒测量Ptp，我们发现它总是以肺部持续气体交换预期导致的速率下降。我们得出结论：1）整个呼吸系统在体内的准静态P-V环面积，以及分别测量的肺脏和胸壁的准静态P-V环面积，均比先前报道的离体肺脏的面积显著更小；2）肺部的持续气体交换对频率设置了下限（相当于持续时间超过5至7秒的气流中断），在该下限以上，体内肺脏的P-流量-V行为才能从纯粹机械角度进行考虑。
