Wilson J R, Ferraro N, Weber K T
Am J Cardiol. 1983 Jun;51(10):1639-43. doi: 10.1016/0002-9149(83)90201-1.
Measurement of blood lactate during exercise in patients with chronic congestive heart failure provides a useful index of oxygen (O2) availability in working muscle. Bicarbonate buffering of lactate produces carbon dioxide (CO2) in excess of that resulting from oxidative metabolism. Therefore, calculation of excess CO2 production from measured CO2 production and O2 uptake may offer a noninvasive quantitative index of changes in blood lactate during exercise in these patients. To investigate this possibility, 22 patients with congestive heart failure and depressed left ventricular function were studied during progressive maximal upright bicycle exercise. Oxygen uptake, expired carbon dioxide, arterial lactate, O2 extraction, and cardiac output were measured at each 20 W incremental work load and peak exercise. Exercise increased VO2 from 3.5 +/- 0.9 ml/min/kg at rest to 13.1 +/- 2.9 ml/min/kg, O2 extraction from 49 +/- 9% at rest to 78 +/- 6%, lactate from 12 +/- 5 mg/dl at rest to 41 +/- 15 mg/dl, and cardiac index from 1.7 +/- 0.4 at rest to 3.8 +/- 1.2 liters/min/m2. The increase in lactate at each work load was linearly related to excess CO2 production (r = 0.92, p less than 0.01). Exercise was repeated the following day in 10 patients; measurements of excess CO2 production was highly reproducible (r = 0.98, p less than 0.01). Excess CO2 production also correlated with the decrease in bicarbonate produced by exercise (r = 0.81), supporting the hypothesis that excess CO2 is produced by bicarbonate buffering of lactate. Thus, calculation of excess carbon dioxide production from noninvasive measurement of respiratory gas exchange provides a reliable and reproducible method of continuously assessing alterations in lactate throughout bicycle exercise in patients with chronic congestive heart failure.
对慢性充血性心力衰竭患者运动期间的血乳酸进行测量，可为工作肌肉中的氧（O2）可用性提供一个有用的指标。乳酸的碳酸氢盐缓冲作用产生的二氧化碳（CO2）超过氧化代谢产生的量。因此，根据测得的CO2产生量和O2摄取量计算过量的CO2产生量，可能为这些患者运动期间血乳酸变化提供一个非侵入性定量指标。为研究这种可能性，对22例充血性心力衰竭且左心室功能降低的患者进行了递增式最大强度直立自行车运动研究。在每次20W递增工作负荷和运动峰值时，测量氧摄取量、呼出二氧化碳量、动脉血乳酸、O2摄取率和心输出量。运动使静息时的VO2从3.5±0.9ml/min/kg增加到13.1±2.9ml/min/kg，O2摄取率从静息时的49±9%增加到78±6%，乳酸从静息时的12±5mg/dl增加到41±15mg/dl，心指数从静息时的1.7±0.4增加到3.8±1.2升/分钟/平方米。每个工作负荷下乳酸的增加与过量CO2产生量呈线性相关（r = 0.92，p<0.01）。次日，对10例患者重复进行运动；过量CO2产生量的测量具有高度可重复性（r = 0.98，p<0.01）。过量CO2产生量也与运动引起的碳酸氢盐减少相关（r = 0.81），支持了过量CO2是由乳酸的碳酸氢盐缓冲作用产生的这一假说。因此，根据呼吸气体交换的非侵入性测量计算过量二氧化碳产生量，为持续评估慢性充血性心力衰竭患者整个自行车运动过程中乳酸变化提供了一种可靠且可重复的方法。
