Janicki J S, Weber K T, McElroy P A
Cardiovascular Institute, Michael Reese Hospital, University of Chicago, Illinois.
Eur Heart J. 1988 Jun;9 Suppl H:55-8. doi: 10.1093/eurheartj/9.suppl_h.55.
Isotonic exercise testing imposes a physiological stress on the cardiopulmonary unit. Accordingly, monitoring of oxygen, carbon dioxide and air flow during an exercise test (i.e. a cardiopulmonary exercise test) can be used to assess heart function in patients with chronic heart failure. Specifically, an incremental treadmill cardiopulmonary exercise test represents a non-invasive means to determine aerobic capacity, or maximal oxygen uptake (VO2max ml min-1 kg-1), and anaerobic threshold (AT, ml min-1 kg-1). These objective measures of cardiopulmonary function are then used to grade the severity of failure and the functional capacity of the patient. In addition, they may be used to predict the cardiac reserve, or maximal cardiac index (CImax, l min-1 m-2) during exercise. That is, the severity is considered to be mild (class A) when AT greater than 14 or VO2max greater than 20, mild to moderate (class B) when AT falls between 11 and 14 or VO2max between 16 and 20, moderate to severe (class C) when AT ranges between 8 and 11 or VO2max between 10 and 16, and severe (class D) when AT less than 8 or VO2max less than 10. The predicted CImax for classes A, B, C and D are greater than 8, 6-8, 4-6 and less than 4, respectively. Finally, a major objective of medical therapy in patients with heart failure is to improve cardiac output and oxygen delivery to working skeletal muscle and thereby enhance effort tolerance. This therapeutic endpoint can be gauged by cardiopulmonary exercise testing from the response in AT and VO2max.
等张运动测试会给心肺系统带来生理压力。因此，在运动测试（即心肺运动测试）过程中监测氧气、二氧化碳和气流，可用于评估慢性心力衰竭患者的心脏功能。具体而言，递增式平板心肺运动测试是一种确定有氧能力或最大摄氧量（VO2max，毫升/分钟/千克）以及无氧阈（AT，毫升/分钟/千克）的非侵入性方法。这些心肺功能的客观指标随后用于对心力衰竭的严重程度和患者的功能能力进行分级。此外，它们还可用于预测运动期间的心脏储备或最大心脏指数（CImax，升/分钟/平方米）。也就是说，当AT大于14或VO2max大于20时，严重程度被认为是轻度（A类）；当AT在11至14之间或VO2max在16至20之间时，为轻度至中度（B类）；当AT在8至11之间或VO2max在10至16之间时，为中度至重度（C类）；当AT小于8或VO2max小于10时，为重度（D类）。A、B、C和D类的预测CImax分别大于8、6 - 8、4 - 6和小于4。最后，心力衰竭患者药物治疗的一个主要目标是改善心输出量和向工作骨骼肌的氧气输送，从而提高耐力。这个治疗终点可以通过心肺运动测试中AT和VO2max的反应来衡量。
