McLellan T M
Environmental Physiology Section, Defence and Civil Institute of Environmental Medicine, North York, Ontario, Canada.
Eur J Appl Physiol Occup Physiol. 1991;63(1):6-11. doi: 10.1007/BF00760793.
The purpose of the present study was to examine the influence of a respiratory acidosis on the blood lactate (La) threshold and specific blood La concentrations measured during a progressive incremental exercise test. Seven males performed three step-incremental exercise tests (20 W.min-1) breathing the following gas mixtures; 21% O2 balance-nitrogen, and 21% O2, 4% CO2 balance-nitrogen or balance-helium. The log-log transformation of La oxygen consumption (VO2) relationship and a 1 mmol.l-1 increase above resting values were used to determine a La threshold. Also, the VO2 corresponding to a La value of 2 (La2) and 4 (La4) mmol.l-1 was determined. Breathing the hypercapnic gas mixtures significantly increased the resting partial pressure of carbon dioxide (PCO2) from 5.6 kPa (42 mm Hg) to 6.1 kPa (46 mm Hg) and decreased pH from 7.395 to 7.366. During the incremental exercise test, PCO2 increased significantly to 7.2 kPa (54 mm Hg) and 6.8 kPa (51 mm Hg) for the hypercapnic gas mixtures with nitrogen and helium, respectively, and pH decreased to 7.194 and 7.208. In contrast, blood PCO2 decreased to 4.9 kPa (37 mm Hg) at the end of the normocapnic exercise test and pH decreased to 7.291. A blood La threshold determined from a log-log transformation [1.20 (0.28) l.min-1] or as an increase of 1 mmol.l-1 [1.84 (0.46) l.min-1] was unaffected by the acid-base alterations. Similarly, the VO2 corresponding to La2 and La4 was not affected by breathing the hypercapnic gas mixtures [2.12 (0.46) l.min-1 and 2.81 (0.52) l.min-1, respectively].(ABSTRACT TRUNCATED AT 250 WORDS)
本研究的目的是检验呼吸性酸中毒对在递增负荷运动试验中测得的血乳酸（La）阈值及特定血La浓度的影响。七名男性进行了三次逐步递增运动试验（20W·min⁻¹），分别呼吸以下气体混合物：21%氧气-其余为氮气、21%氧气、4%二氧化碳-其余为氮气或其余为氦气。采用La与耗氧量（VO₂）关系的对数-对数转换以及比静息值增加1mmol·L⁻¹来确定La阈值。此外，还确定了对应于La值为2（La₂）和4（La₄）mmol·L⁻¹时的VO₂。呼吸高碳酸血症气体混合物显著使静息二氧化碳分压（PCO₂）从5.6kPa（42mmHg）升至6.1kPa（46mmHg），pH从7.395降至7.366。在递增运动试验期间，对于含氮气和氦气的高碳酸血症气体混合物，PCO₂分别显著升至7.2kPa（54mmHg）和6.8kPa（51mmHg），pH降至7.194和7.208。相比之下，在正常碳酸血症运动试验结束时血PCO₂降至4.9kPa（37mmHg），pH降至7.291。通过对数-对数转换确定的血La阈值[1.20（0.28）L·min⁻¹]或比静息值增加1mmol·L⁻¹时的阈值[1.84（0.46）L·min⁻¹]不受酸碱改变的影响。同样，对应于La₂和La₄的VO₂也不受呼吸高碳酸血症气体混合物的影响[分别为2.12（0.46）L·min⁻¹和2.81（0.52）L·min⁻¹]。（摘要截断于250字）
