Rajagopalan B, Bertram C D, Stallard T, Lee G D
Cardiovasc Res. 1979 Dec;13(12):684-92. doi: 10.1093/cvr/13.12.684.
Vein flow in the large extraparenchymal pulmonary veins is pulsatile and its wave form has an inverse relationship to left atrial pressure. Extraparenchymal pulmonary veins are thin walled and collapsible. This enables them to behave as highly compliant structures. Dimensional measurements of their cross sectional area in living open chested dogs showed them to be non circular at low left atrial pressures. They rapidly assumed a circular cross section as left atrial pressure rose. Only at pressures above 1.5 kPa (11 mmHg) were the pulmonary veins circular in cross section. The aggregate volume of the large extraparenchymal pulmonary veins, when fully distended, was found to be equal to or greater than one stroke volume of the heart. The extraparenchymal pulmonary veins act as a reservoir to the left atrium so that left ventricular stroke volume can be maintained relatively unaffected by beat by beat changes in right ventricular stroke output. Their behaviour at normal mean left atrial pressures also enables them to isolate the lung capillaries from retrograde transmission of positive pressure transients from the left atrium, which could otherwise impede venous outflow of blood from the lung capillary bed.
肺实质外大静脉的血流是搏动性的，其波形与左心房压力呈反比关系。肺实质外肺静脉壁薄且可塌陷。这使得它们能够表现为顺应性很高的结构。在开胸的活体犬中对其横截面积进行的尺寸测量显示，在左心房压力较低时它们是非圆形的。随着左心房压力升高，它们迅速呈现圆形横截面。只有在压力高于1.5千帕（11毫米汞柱）时，肺静脉的横截面才是圆形的。当完全扩张时，肺实质外大静脉的总体积被发现等于或大于心脏的每搏输出量。肺实质外肺静脉起到左心房的一个储血库的作用，这样左心室每搏输出量能够相对不受右心室每搏输出量逐搏变化的影响而得以维持。它们在正常平均左心房压力下的表现还使它们能够将肺毛细血管与来自左心房的正压瞬变的逆行传导隔离开来，否则这种传导可能会阻碍血液从肺毛细血管床的静脉流出。
