Pellett A A, Cairo J M, Levitzky M G
Department of Cardiopulmonary Science, Louisiana State University Medical Center, New Orleans 70112-1393, USA.
Respir Physiol. 1997 Sep;109(3):249-60. doi: 10.1016/s0034-5687(97)00055-8.
Hypoxemia interferes with hypoxic pulmonary vasoconstriction (HPV). We investigated the respective roles of the autonomic nervous system and the mixed venous PO2 (PVO2) in the attenuation of HPV by hypoxemia. Pentobarbital-anesthetized dogs had their lungs separately ventilated with a dual-lumen endotracheal tube. Left (Ql) and total (Qt) pulmonary blood flows were determined using electromagnetic flow probes. HPV was initiated by ventilating the left lung with nitrogen for 5-10 min while the right lung received 100% oxygen. The animals were subsequently made hypoxemic by switching the right lung to room air ventilation (5-10 min). Two different protocol groups received either intravenous atropine during hypoxemia (group I) or intravenous propranolol prior to protocol initiation (group II). A third group of dogs (group III) had their mixed venous PO2S maintained above 30 torr during hypoxemia. In response to left lung hypoxia, Ql/Qt decreased from 44 +/- 5, 48 +/- 3 and 46 +/- 2% to 25 +/- 4, 28 +/- 2 and 26 +/- 3% in the three groups, respectively. During hypoxemia Ql/Qt increased to 50 +/- 7 and 47 +/- 3% in groups I and II. In group III dogs, Ql/Qt remained significantly decreased at 31 +/- 3%. Subsequent administration of atropine in group I had no effect on Ql/Qt. We conclude that the loss of flow diversion from a hypoxic lung during hypoxemia may be mediated primarily by a decreased in mixed venous PO2 when PVO2 is allowed to decrease to 15-20 torr.
低氧血症会干扰低氧性肺血管收缩（HPV）。我们研究了自主神经系统和混合静脉血氧分压（PVO2）在低氧血症减弱HPV过程中各自的作用。用戊巴比妥麻醉的犬通过双腔气管导管分别对其肺进行通气。使用电磁流量探头测定左肺（Ql）和总肺（Qt）血流量。通过用氮气对左肺通气5 - 10分钟，同时右肺接受100%氧气来启动HPV。随后通过将右肺切换至室内空气通气（5 - 10分钟）使动物出现低氧血症。两个不同的方案组在低氧血症期间分别接受静脉注射阿托品（I组）或在方案开始前接受静脉注射普萘洛尔（II组）。第三组犬（III组）在低氧血症期间将其混合静脉血氧分压维持在30托以上。对左肺缺氧的反应中，三组中Ql/Qt分别从44±5%、48±3%和46±2%降至25±4%、28±2%和26±3%。在低氧血症期间，I组和II组的Ql/Qt分别升至50±7%和47±3%。在III组犬中，Ql/Qt仍显著降低至31±3%。随后在I组中给予阿托品对Ql/Qt无影响。我们得出结论，当PVO2降至15 - 20托时，低氧血症期间低氧肺血流分流的丧失可能主要由混合静脉血氧分压降低介导。
