Jayaweera A R, Ehrlich W
Division of Environmental Physiology, Johns Hopkins University School of Hygiene and Public Health, Baltimore, MD 21205.
Ann Biomed Eng. 1987;15(3-4):311-8. doi: 10.1007/BF02584286.
Eighty experiments were performed with nine awake dogs to study the changes of phasic-pleural pressure with exercise. The increased minute volume with exercise was obtained by more frequent pleural pressure swings and by a substantial extension of the pressure swings in both directions. The cyclic changes of stroke volume following the pressure swings support the hypothesis that alterations of pleural pressure affect the stroke volume and can act, if necessary, as a secondary pump for the circulation. Mean pleural pressure during exercise fell by 2.5 cm H2O from the rest value of 12.1 cm H2O. The absolute right atrial pressure during exercise (-2.69 mm Hg) was not different from that at rest (-2.39 mm Hg). However, the transmural right atrial pressure of 7.6 mm Hg during exercise was higher than the pressure of 6.2 mm Hg at rest because during exercise the right atrium was perfused by 38% higher blood flow than that at rest. The phasic pattern of right atrial pressure shows that there is good reason to assume that during inspiration the extrathoracic veins are collapsed at their entrance into the chest, but this collapse is removed during expiration. There is no reason to assume an effective, sustained collapse of extrathoracic veins. Rather we can visualize a rhythmical change of flow in extrathoracic veins from transient limitation to transient acceleration.
用9只清醒的狗进行了80次实验，以研究运动时相性胸膜腔内压的变化。运动时每分通气量的增加是通过更频繁的胸膜腔内压波动以及两个方向上压力波动的显著扩展来实现的。压力波动后每搏输出量的周期性变化支持这样一种假说，即胸膜腔内压的改变会影响每搏输出量，并且在必要时可作为循环的辅助泵。运动期间的平均胸膜腔内压从静息值12.1 cm H₂O下降了2.5 cm H₂O。运动期间的绝对右心房压（-2.69 mmHg）与静息时（-2.39 mmHg）没有差异。然而，运动期间的跨壁右心房压为7.6 mmHg，高于静息时的6.2 mmHg，因为运动期间右心房的灌注血流量比静息时高38%。右心房压的时相模式表明，有充分理由假定在吸气时胸外静脉在进入胸部处塌陷，但在呼气时这种塌陷消失。没有理由假定胸外静脉会发生有效、持续的塌陷。相反，我们可以设想胸外静脉内血流从短暂受限到短暂加速的节律性变化。
