Hazinski T A, Kennedy K A
Department of Pediatrics, Vanderbilt University, School of Medicine, Nashville, Tennessee 37232.
Pediatr Res. 1987 Dec;22(6):679-82. doi: 10.1203/00006450-198712000-00013.
Alveolar hypoxia increases pulmonary artery pressure in lambs and sheep but increases lung lymph flow only in lambs; the reasons for this are unknown. To test the hypothesis that hypoxia-induced pulmonary venous constriction could in part explain the fluid filtration response in young lambs, eight young lambs (13 +/- 3 days old) and four older lambs (60 +/- 4 days old) were prepared for chronic studies of pulmonary hemodynamics, gas exchange, and fluid filtration. In all animals, a 5 Fr catheter was intermittently wedged into a distal pulmonary artery to indirectly estimate pulmonary venous pressure. The pressure measured in this manner was termed the "small wedge pressure." Animals were awake, spontaneously breathing, and unsedated, and were exposed to both acute and chronic isocarbic hypoxia (FIO20.12). We found that hypoxia significantly increased both small pulmonary wedge pressure and lung lymph flow in young lambs but that neither of these effects occurred in the older lambs. In young lambs, the hypoxia-induced increase in small wedge pressure could be lowered by sodium nitroprusside administration, and small wedge pressure could be increased by angiotensin II infusion. We conclude that alveolar hypoxia increases pulmonary venous tone and the critical pressure of pulmonary veins in young lambs, and that these effects disappear with maturation. These data suggest that alterations in pulmonary venous tone can have important effects on lung fluid balance in the newborn.
肺泡低氧会增加羔羊和绵羊的肺动脉压力，但仅会增加羔羊的肺淋巴流量；其原因尚不清楚。为了验证低氧诱导的肺静脉收缩可能部分解释幼龄羔羊液体滤过反应的这一假说，八只幼龄羔羊（13±3日龄）和四只老龄羔羊（60±4日龄）被准备用于肺血流动力学、气体交换和液体滤过的慢性研究。在所有动物中，将一根5F导管间歇性楔入远端肺动脉以间接估计肺静脉压力。以这种方式测得的压力被称为“小楔压”。动物处于清醒、自主呼吸且未使用镇静剂的状态，并暴露于急性和慢性等碳酸血症低氧（吸入氧分数0.12）环境中。我们发现，低氧显著增加了幼龄羔羊的小肺楔压和肺淋巴流量，但在老龄羔羊中这两种效应均未出现。在幼龄羔羊中，硝普钠给药可降低低氧诱导的小楔压升高，而输注血管紧张素II可增加小楔压。我们得出结论，肺泡低氧会增加幼龄羔羊的肺静脉张力和肺静脉临界压力，且这些效应会随着成熟而消失。这些数据表明，肺静脉张力的改变可能对新生儿的肺液体平衡产生重要影响。
