Suarez J, Alexander J K, Houston C S
Am J Cardiol. 1987 Jul 1;60(1):137-42. doi: 10.1016/0002-9149(87)91000-9.
Serial rest and upright cycle exercise 2-dimensional echocardiographic studies were performed in 7 healthy young men during acclimatization to a simulated altitude of 29,000 feet (barometric pressure [PB] 240 torr) in a chamber for 40 days. In all subjects left ventricular (LV) end-diastolic, end-systolic and stroke volumes progressively decreased, with mean reductions of 21%, 40% and 14%, respectively, on ascent to 25,000 feet (PB 282 torr) at rest, and reductions of 23%, 43% and 14% during 60-W exercise. At PB 282 torr, mean arterial blood O2 partial pressures were 37 torr (rest) and 32 torr (exercise), with corresponding O2 saturations of 68% and 59%. All 3 indexes of LV systolic function examined--ejection fraction, ratio of peak systolic pressure to end-systolic volume and mean normalized systolic ejection rate at rest--were sustained in all subjects at high altitude despite reduced preload, pulmonary hypertension and severe hypoxemia. Increases in ejection fraction of 6% at rest and 10% during exercise developed at PB 282 torr and a higher mean normalized systolic ejection rate in association with elevated circulating catecholamines reflecting enhanced sympathetic activity. LV systolic function is not a limiting factor in compromising the exercise capacity of normal humans on ascent to high altitude, even to the peak of Mt. Everest.
对7名健康年轻男性在海拔29,000英尺（气压[PB]240托）的模拟高原环境中进行40天适应性训练期间，进行了系列静息和直立周期运动二维超声心动图研究。在所有受试者中，左心室（LV）舒张末期、收缩末期和每搏量逐渐减少，在静息状态下上升到25,000英尺（PB 282托）时，平均减少分别为21%、40%和14%，在60瓦运动期间减少分别为23%、43%和14%。在PB 282托时，平均动脉血氧分压在静息时为37托，运动时为32托，相应的血氧饱和度分别为68%和59%。尽管前负荷降低、肺动脉高压和严重低氧血症，但在高海拔地区，所有受试者静息时检查的左心室收缩功能的所有3项指标——射血分数、收缩压峰值与收缩末期容积之比以及平均标准化收缩射血率——均得以维持。在PB 282托时，静息时射血分数增加6%，运动时增加10%，并且平均标准化收缩射血率更高，同时循环儿茶酚胺升高，反映交感神经活动增强。左心室收缩功能不是正常人上升到高海拔地区（甚至到珠穆朗玛峰顶峰）时损害运动能力的限制因素。
