Limitations of continuous long-term ventilation in the prone position

研究体位对低氧机械通气家兔体内血流动力学的影响，以及对体外低氧肺（离体灌注肺）损伤程度的影响。俯卧位组的心率和心率压值较高，而仰卧位组的心输出量、耗氧量、供氧量和动静脉氧差值较高。俯卧组的压力变化和仰卧组的血流变化被认为是对缺氧的反应。灌注肺干湿比显著增高，缺氧负荷后肺水毛细血管滤过系数显著增高。在低氧状态下的长期通气对于易感组来说显然是有问题的，因为大量的血液聚集在肺部。

The effects of body position on hemodynamics during hypoxic mechanical ventilation in rabbits in vivo, and on the degree of lung damage caused by hypoxia in vitro (isolated perfused lung) were investigated. Values for heart rates and rate pressure products were high in the prone group, whereas those for cardiac output, oxygen consumption, oxygen delivery and arteriovenous oxygen difference were high in the supine group. The changes in pressure in the prone group and in flow in the supine group were thought to result from a response to hypoxia. The wet to dry weight ratio of the perfused lung was significantly higher, and the capillary filtration coefficient of lung water after hypoxic loading was significantly increased in the prone group. Long-term ventilation in a hypoxic state was apparently problematic for the prone group, as a large volume of blood pooled in the lungs.