Bencowitz H Z, Wagner P D, West J B
J Appl Physiol Respir Environ Exerc Physiol. 1982 Dec;53(6):1487-95. doi: 10.1152/jappl.1982.53.6.1487.
Acclimatization to altitude often results in a rightward shift of the O2 dissociation curve (ODC). However, a left-shifted ODC is reported to increase exercise tolerance in humans at medium altitude and increase survival in rats breathing hypoxic gas mixtures. We examined this paradox using a computer model of pulmonary gas exchange. A Bohr integration procedure allowed for alveolar-capillary diffusion. When diffusion equilibration was complete, mixed venous (PVO2) and arterial PO2 fell as O2 consumption (VO2) was increased, but PVO2 approached a plateau. Under these conditions a right-shifted ODC is advantageous (higher PVO2) at all but very high altitudes. However, diffusion limitation of O2 transfer may occur at any altitude if VO2 is increased sufficiently. If this occurs, a left-shifted ODC results in higher calculated VO2max (compared with the standard ODC). Further, diffusion limitation always occurs at a lower VO2 with a right-shifted ODC than with a left-shifted ODC. We conclude that whether a leftward or rightward shift in the ODC is advantageous to gas exchange at altitude depends on the presence or absence of diffusion limitation.
对高原环境的适应通常会导致氧解离曲线（ODC）向右移动。然而，据报道，左移的氧解离曲线可提高人类在中等海拔高度的运动耐力，并增加大鼠在呼吸低氧混合气体时的存活率。我们使用肺气体交换计算机模型研究了这一矛盾现象。采用玻尔积分程序来模拟肺泡-毛细血管扩散。当扩散平衡完成后，随着耗氧量（VO2）增加，混合静脉血氧分压（PVO2）和动脉血氧分压（PO2）下降，但PVO2接近一个平台期。在这些条件下，除了极高海拔外，右移的氧解离曲线在所有海拔高度都是有利的（PVO2更高）。然而，如果VO2增加得足够多，在任何海拔高度都可能发生氧气传输的扩散限制。如果发生这种情况，左移的氧解离曲线会导致计算出的最大耗氧量（VO2max）更高（与标准氧解离曲线相比）。此外，与左移的氧解离曲线相比，右移的氧解离曲线总是在更低的VO2时出现扩散限制。我们得出结论，氧解离曲线向左或向右移动对高原气体交换是否有利取决于是否存在扩散限制。
