Bidani A, Crandall E D
J Appl Physiol Respir Environ Exerc Physiol. 1982 Aug;53(2):413-8. doi: 10.1152/jappl.1982.53.2.413.
A mathematical model of the chemical and transport events in blood during and after gas exchange has been used to examine the rates of CO2 excretion (Vco2) and O2 uptake (Vo2) in the lung at different levels of hematocrit (Hct), assuming fixed mixed venous blood O2 and CO2 contents and alveolar gases and constant cardiac output. The results show that a reduction in Hct from 45 to 30% leads to approximately 25% reduction in Vco2 compared with approximately 30% reduction in Vo2. Reduction of Hct from 45 to 15% results in approximately 50% reduction in Vco2 and approximately 63% reduction in Vo2. An increase in Hct from 45 to 60% results in approximately 25% increase in Vco2, accompanied by approximately 30% increase in Vo2. These fractional changes in gas exchange are only slightly affected by the extent of catalysis of the plasma CO2-H2CO3 hydration-dehydration reactions in the pulmonary vasculature. The reduction in Vco2 with reductions in Hct are due to 1) decrease in the total quantity of Bohr protons released during diminution of Vo2, 2) decrease in the size of the high buffer capacity intraerythrocytic pool, and 3) decrease in the total surface area available for HCO-3/Cl- exchange across the red cell membrane. We conclude that hitherto unrecognized changes in Vco2 (in addition to the well-known changes in Vo2) may occur as a consequence of alterations in Hct.
在气体交换期间及之后血液中化学和运输过程的数学模型，已被用于研究在不同血细胞比容（Hct）水平下肺内二氧化碳排出率（Vco2）和氧气摄取率（Vo2），假设混合静脉血中的氧气和二氧化碳含量、肺泡气体固定不变，且心输出量恒定。结果表明，血细胞比容从45%降至30%时，Vco2约降低25%，而Vo2约降低30%。血细胞比容从45%降至15%时，Vco2约降低50%，Vo2约降低63%。血细胞比容从45%增至60%时，Vco2约增加25%，同时Vo2约增加30%。气体交换的这些分数变化仅略微受肺血管系统中血浆CO2 - H2CO3水合 - 脱水反应催化程度的影响。随着血细胞比容降低，Vco2降低的原因如下：1）Vo2减少期间释放的波尔质子总量减少；2）高缓冲能力红细胞内池的大小减小；3）红细胞膜上可用于HCO - 3/Cl - 交换的总表面积减小。我们得出结论，血细胞比容改变可能导致Vco2出现迄今未被认识到的变化（除了众所周知的Vo2变化）。
