Beaver W L, Wasserman K, Whipp B J
J Appl Physiol (1985). 1986 Jun;60(6):2020-7. doi: 10.1152/jappl.1986.60.6.2020.
Excess CO2 is generated when lactate is increased during exercise because its [H+] is buffered primarily by HCO-3 (22 ml for each meq of lactic acid). We developed a method to detect the anaerobic threshold (AT), using computerized regression analysis of the slopes of the CO2 uptake (VCO2) vs. O2 uptake (VO2) plot, which detects the beginning of the excess CO2 output generated from the buffering of [H+], termed the V-slope method. From incremental exercise tests on 10 subjects, the point of excess CO2 output (AT) predicted closely the lactate and HCO-3 thresholds. The mean gas exchange AT was found to correspond to a small increment of lactate above the mathematically defined lactate threshold [0.50 +/- 0.34 (SD) meq/l] and not to differ significantly from the estimated HCO-3 threshold. The mean VO2 at AT computed by the V-slope analysis did not differ significantly from the mean value determined by a panel of six experienced reviewers using traditional visual methods, but the AT could be more reliably determined by the V-slope method. The respiratory compensation point, detected separately by examining the minute ventilation vs. VCO2 plot, was consistently higher than the AT (2.51 +/- 0.42 vs. 1.83 +/- 0.30 l/min of VO2). This method for determining the AT has significant advantages over others that depend on regular breathing pattern and respiratory chemosensitivity.
运动期间乳酸增加时会产生过量二氧化碳，因为其[H⁺]主要由HCO₃⁻缓冲（每毫当量乳酸缓冲22毫升）。我们开发了一种检测无氧阈（AT）的方法，利用对二氧化碳摄取量（VCO₂）与氧气摄取量（VO₂）关系图斜率进行计算机回归分析，该方法可检测因[H⁺]缓冲产生的过量二氧化碳输出的起始点，称为V斜率法。通过对10名受试者进行递增运动测试，过量二氧化碳输出点（AT）与乳酸和HCO₃⁻阈值密切相关。发现平均气体交换AT对应于乳酸在数学定义的乳酸阈值之上的小幅增加[0.50±0.34（标准差）毫当量/升]，且与估计的HCO₃⁻阈值无显著差异。通过V斜率分析计算的AT时的平均VO₂与由六名经验丰富的评审员使用传统视觉方法确定的平均值无显著差异，但V斜率法能更可靠地确定AT。通过检查分钟通气量与VCO₂关系图单独检测的呼吸补偿点始终高于AT（VO₂分别为2.51±0.42与1.83±0.30升/分钟）。这种确定AT的方法比其他依赖正常呼吸模式和呼吸化学敏感性的方法具有显著优势。
