Toga H, Okazaki H, Ishigaki M, Noguchi T, Huang J, Fukunaga T, Nagasaka Y, Takahashi K, Ohya N
Division of Respiratory Diseases, Department of Internal Medicine, Kanazawa Medical University, Uchinada, Ishikawa 920-0265, Japan.
J Appl Physiol (1985). 1998 Mar;84(3):1003-10. doi: 10.1152/jappl.1998.84.3.1003.
To investigate the effect of alveolar hypoxia on the pulmonary blood flow-segmental vascular resistance relationship, we determined the longitudinal distribution of vascular resistance while increasing blood flow during hyperoxia or hypoxia in perfused cat lungs. We measured microvascular pressures by the micropipette servo-null method, partitioned the pulmonary vessels into three segments [i.e., arterial (from main pulmonary artery to 30- to 50-micron arterioles), venous (from 30- to 50-micron venules to left atrium), and microvascular (between arterioles and venules) segments] and calculated segmental vascular resistance. During hyperoxia, total resistance decreased with increased blood flow because of a reduction of microvascular resistance. In contrast, during hypoxia, not only microvascular resistance but also arterial resistance decreased with increase of blood flow while venous resistance remained unchanged. The reduction of arterial resistance was presumably caused by arterial distension induced by an elevated arterial pressure during hypoxia. We conclude that, during hypoxia, both microvessels and arteries >50 micron in diameter play a role in preventing further increases in total pulmonary vascular resistance with increased blood flow.
为研究肺泡低氧对肺血流-节段性血管阻力关系的影响，我们在灌注猫肺的高氧或低氧状态下增加血流时，测定了血管阻力的纵向分布。我们采用微吸管伺服零位法测量微血管压力，将肺血管分为三个节段[即动脉段（从主肺动脉到30 - 50微米的小动脉）、静脉段（从30 - 50微米的小静脉到左心房）和微血管段（在小动脉和小静脉之间）]，并计算节段性血管阻力。在高氧状态下，由于微血管阻力降低，总阻力随血流增加而下降。相反，在低氧状态下，不仅微血管阻力，而且动脉阻力也随血流增加而降低，而静脉阻力保持不变。动脉阻力的降低可能是由于低氧时动脉压升高引起的动脉扩张所致。我们得出结论，在低氧状态下，直径>50微米的微血管和动脉在防止随着血流增加肺血管总阻力进一步升高方面发挥作用。
