Cruz J C, Grover R F, Reeves J T, Maher J T, Cymerman A, Denniston J C
J Appl Physiol. 1976 Jan;40(1):96-100. doi: 10.1152/jappl.1976.40.1.96.
Venoconstriction occurs at high altitude. This study sought to determine whether hypoxia or hypocapnia is the cause of the venoconstriction. Five male subjects were exposed to 4,000-4,400 m (PB 440-465 mmHg) with supplemental 3.77 +/- 0.02% CO2 in a hypobaric chamber for 4 days. Similar alveolar O2 tensions were obtained in four control subjects exposed to 3,500-4,100 m (PB 455-492 mmHg) without CO2. A water-filled plethysmograph was used to determine forearm flow and venous compliance. Systemic blood pressure was measured with the cuff procedure. Catecholamines were measured in 24-h urine collections. Venous compliance fell at high altitude in both groups and was less (P less than 0.01) than control values. Forearm flow and resistance were unaltered at altitude in the group with CO2 supplementation while forearm flow decreased and resistance increased in the hypocapnic group at 72 h of exposure. Urinary catecholamines increased in the group with CO2 and remained unaltered in the hypocapnic group. It is concluded that hypoxia is responsible for decreasing venous compliance, and hypocapnia for increasing resistance and decreasing flow. Group differences observed in urinary catecholamines may be explained by differences in arterial pH.
在高海拔地区会发生静脉收缩。本研究旨在确定低氧或低碳酸血症是否为静脉收缩的原因。五名男性受试者在低压舱中暴露于海拔4000 - 4400米（气压440 - 465 mmHg）环境，并补充3.77±0.02%的二氧化碳，持续4天。四名对照受试者暴露于海拔3500 - 4100米（气压455 - 492 mmHg）环境且不补充二氧化碳，获得了相似的肺泡氧分压。使用充水体积描记器来测定前臂血流量和静脉顺应性。采用袖带法测量全身血压。收集24小时尿液以测定儿茶酚胺。两组在高海拔地区静脉顺应性均下降，且低于（P<0.01）对照值。补充二氧化碳组在高海拔地区前臂血流量和阻力未改变，而低碳酸血症组在暴露72小时时前臂血流量减少且阻力增加。补充二氧化碳组尿儿茶酚胺增加，低碳酸血症组则保持不变。结论是，低氧导致静脉顺应性降低，低碳酸血症导致阻力增加和血流量减少。尿儿茶酚胺中观察到的组间差异可能由动脉pH值差异来解释。
