Seith U
Prax Klin Pneumol. 1979 Apr;33 Suppl 1:379-82.
The pleural cavity, because of the thin film of fluid between the pleural layers, acts like a capillary space within which capillary forces operate. It is due to these forces that the lungs follow the respiratory movements of the thoracic cage and diaphragm and are kept expanded within the thorax. "Subatmospheric" pressure in the pleural cavity develops only if the capillary space is opened by injury to one of the pleural layers, thus allowing the elastic pull of the thoracic cage and lungs to act on the pleural cavity. The subatmospheric pressure registered by the exploratory needle is, in fact, non-existent in the normal chest. It owes its existence to the introduction of the needle which causes separation of the pleural layers and the introduction of a small quantity of air. The pulling and stretching forces exerted by the thorax and lungs on the air bubble then become measurable as subatmospheric pressure. The same forces operate during the respiratory movements and induce changes in volume and pressure in all air or fluid containing spaces. The result is a delicately regulated consonance of aire movement and blood distribution. Simplified graphs illustrate the interconnections.
由于胸膜层之间存在薄薄的一层液体，胸膜腔就像一个毛细血管间隙，毛细血管力在其中起作用。正是由于这些力，肺才会随着胸廓和膈肌的呼吸运动而运动，并在胸腔内保持扩张状态。只有当胸膜层之一因受伤而使毛细血管间隙开放时，胸膜腔内才会产生“低于大气压”的压力，从而使胸廓和肺的弹性拉力作用于胸膜腔。事实上，用穿刺针测得的低于大气压的压力在正常胸腔中并不存在。它的存在是由于穿刺针的插入导致胸膜层分离并引入了少量空气。然后，胸廓和肺对气泡施加的拉力和张力就可以作为低于大气压的压力来测量。在呼吸运动过程中，同样的力也在起作用，并导致所有含气或含液空间的体积和压力发生变化。结果是空气运动和血液分布得到了精确调节的协调。简化的图表说明了它们之间的相互关系。
