Raj J U, Chen P, Navazo L
Am J Physiol. 1987 Jan;252(1 Pt 2):H80-4. doi: 10.1152/ajpheart.1987.252.1.H80.
We have examined the effect of positive pressure inflation on the longitudinal distribution of vascular resistance and intravascular pressures in isolated blood-perfused lungs of 3- to 4-wk-old rabbits. Lungs were perfused in zone 3 at airway inflation pressures (P airway) of 6, 14, and 19 cmH2O (pleural pressure, atmospheric) corresponding to 60, 80, and 90% of total lung capacity. We measured microvascular pressures by the micropipette servo-nulling technique in 20- to 50-microns diameter subpleural arterioles and venules. Pulmonary arterial and left atrial pressures were also measured. Lung blood flow was kept constant at 145 +/- 18 ml X kg body wt-1 X min-1. We found that at P airway of 6 cmH2O, approximately 55% of the total pressure drop was in arteries, approximately 23% in microvessels, and approximately 22% in veins. With increasing P airway and lung volume, there was a significant decrease in arterial and venous resistance, but an increase in resistance in microvessels. We conclude that lung inflation significantly alters the distribution of segmental vascular resistance, and therefore lung volume is an important variable that should be considered during estimation of capillary filtration pressure.
我们研究了正压通气对3至4周龄兔离体血液灌注肺血管阻力和血管内压力纵向分布的影响。在气道充气压力(P气道)分别为6、14和19 cmH₂O(胸膜压力为大气压)的情况下对肺进行灌注,这些压力分别对应肺总量的60%、80%和90%,处于第3灌注区。我们采用微吸管伺服归零技术测量直径为20至50微米的胸膜下小动脉和小静脉中的微血管压力。同时也测量肺动脉和左心房压力。肺血流量保持恒定,为145±18 ml·kg体重⁻¹·min⁻¹。我们发现,在P气道为6 cmH₂O时,总压力降的约55%存在于动脉中,约23%存在于微血管中,约22%存在于静脉中。随着P气道和肺容积增加,动脉和静脉阻力显著降低,但微血管阻力增加。我们得出结论,肺充气显著改变节段性血管阻力的分布,因此在估计毛细血管滤过压时,肺容积是一个应予以考虑的重要变量。