Thorvaldson J, Ilebekk A, Kiil F
Acta Physiol Scand. 1985 Nov;125(3):471-9. doi: 10.1111/j.1748-1716.1985.tb07744.x.
To examine the effects of airway pressure (AWP) on pulmonary blood volume (PBV) at various pulmonary vascular pressures and flows, experiments were performed in anaesthetized, open-chest dogs. The AWP was raised by elevating end-expiratory pressure, and PBV was calculated as the product of electromagnetic aortic flow and pulmonary mean transit time for ascorbate (polarographic method). When AWP was raised from 3 to 13 mmHg, changing lung conditions from zone 3 [left atrial pressure (LAP) higher than AWP] to zone 2 (AWP higher than LAP), PBV decreased by 14.5 +/- 6.2%. When LAP was raised above 7 mmHg at constant pulmonary arterial pressure (PAP), PBV increased under zone 2 but not under zone 3 conditions. During blood volume expansion to LAP 15 mmHg, PBV rose by 30-50% and became equal at AWP of 4 and 14 mmHg, whereas the pulmonary vascular resistance remained 40% higher at high AWP. These data suggest that PAP, LAP and AWP regulate PBV by acting on compliant vessels surrounding the alveoli. Under zone 2 conditions with collapsed aveolar capillaries, elevation of LAP results in re-expansion of the alveolar capillaries, and PBV is restored without a rise in PAP. Under zone 3 conditions, a rise in LAP cannot increase PBV without raising PAP, explaining why PBV remains constant when PAP is kept constant.
为了研究在不同肺血管压力和血流情况下气道压力（AWP）对肺血容量（PBV）的影响，在麻醉开胸犬身上进行了实验。通过提高呼气末压力来升高AWP，PBV通过电磁主动脉血流与抗坏血酸肺平均通过时间的乘积来计算（极谱法）。当AWP从3 mmHg升高到13 mmHg时，肺状态从3区[左心房压力（LAP）高于AWP]转变为2区（AWP高于LAP），PBV下降了14.5±6.2%。当在恒定肺动脉压（PAP）下将LAP升高到7 mmHg以上时，在2区条件下PBV增加，但在3区条件下则不然。在血容量扩充至LAP为15 mmHg期间，PBV升高了30 - 50%，在AWP为4 mmHg和14 mmHg时相等，而在高AWP时肺血管阻力仍高出40%。这些数据表明，PAP、LAP和AWP通过作用于肺泡周围的顺应性血管来调节PBV。在肺泡毛细血管塌陷的2区条件下，LAP升高导致肺泡毛细血管重新扩张，PBV得以恢复而PAP不升高。在3区条件下，LAP升高而不升高PAP则无法增加PBV，这解释了为什么当PAP保持恒定时PBV保持不变。
