traditional values？怎么理解？

Quantification of the Diffusing Capacity for Oxygen

The diffusing capacity of oxygen is simply the oxygen uptake divided by the partial pressure gradient from alveolar gas to pulmonary capillary blood, where the relevant value is the mean pulmonary capillary Po2:

O₂弥散能力的量化

O₂的弥散量仅是氧摄取量除以肺泡气至肺毛细血管血的氧分压差，其中肺毛细血管血的氧分压是平均肺毛细血管PO₂：

氧弥散量= 氧摄取量/（肺泡PO₂-肺毛细血管平均PO₂）

The alveolar Po2 can be derived with some degree of accuracy (page 107), but there are very serious problems in estimating the mean pulmonary capillary Po2. It is clearly impossible to make a direct measurement of the mean Po2 of the pulmonary capillary blood, and therefore attempts have been made to derive this quantity indirectly from the presumed changes of Po2 that occur as blood passes through the pulmonary capillaries.

肺泡PO₂的推导具有一定程度的准确性（第107页），但准确估计肺毛细血管平均PO₂时却很困难。我们显然不可能直接测定肺毛细血管血的平均PO₂，因此已尝试从血液通过肺毛细血管时的假定PO₂变化间接推导该量。

The earliest analysis of the problem was made by Bohr in 1909. He made the assumption that, at any point along the pulmonary capillary, the rate of diffusion of oxygen was proportional to the Po2 difference between the alveolar gas and the pulmonary capillary blood at that point. Using this approach, and assuming a value for the alveolar/pulmonary end-capillary Po2 gradient, it seemed possible to construct a graph of capillary Po2 plotted against the time the blood had been in the pulmonary capillary. A typical curve drawn on this basis is shown as the broken blue line in Figure 8.2, A. Once the curve has been drawn, it is relatively easy to derive the mean pulmonary capillary Po2, which then permits calculation of the oxygen-diffusing capacity. The validity of the assumption of the alveolar/pulmonary end- capillary Po2 gradient is considered later.

Bohr于1909年最早对这个问题进行了的分析。⁸他假设，在肺毛细血管的任何一点上，氧的弥散速率与该点肺泡气体和肺毛细血管血液之间的PO₂差成正比。使用这种方法，并假设肺泡/肺毛细血管PO₂梯度值，似乎可构建一个毛细血管PO₂对血液在肺毛细血管中的时间的关系图。在此基础上绘制的典型曲线如图8.2，A中的蓝色虚线所示。绘制曲线后，相对容易推导出平均肺毛细血管PO₂，从而可以计算氧气弥散量。肺泡/肺末梢毛细血管PO₂梯度假设的有效性会在后面进行讨论。

Each graph shows the rise in blood Po2 as blood passes along the pulmonary capillaries. The horizontal line at the top of the graph indicates the alveolar Po2 that the blood Po2 is approaching. In (A) the subject is breathing air, whereas in (B) the subject is breathing about 14% oxygen. The broken blue curve shows the rise in Po2 cal­culated according to the Bohr procedure on an assumed value for the alveolar/end-capillary Po2 gradient. The continuous red curve shows the values obtained by forward integration. Horizontal bars indicate mean pulmonary capillary Po2 calculated from each curve.

从左向右、从上向下

A：Blood PO₂（kPa）血液PO₂（kPa），Alveolar PO₂ 13.3kPa（100mmHg）肺泡PO₂ 13.3 kPa（100 mmHg），Blood PO₂（mmHg）血液PO₂（mmHg）

B：Blood PO₂（kPa）血液PO₂（kPa），Alveolar PO₂ 8kPa（60mmHg）肺泡PO₂ 8 kPa（60 mmHg），Blood PO₂（mmHg）血液PO₂（mmHg）

•图8.2每张图表显示血液经肺毛细血管流动时PO₂的上升。图表顶部的水平线表示血PO₂正在接近的肺泡PO₂。（A）受试者呼吸空气，而（B）受试者呼吸约14% 的O₂。虚线蓝色曲线显示根据Bohr公式计算的肺泡/毛细血管末端 PO₂梯度的假设值上的 PO₂上升。连续的红色曲线显示了前向积分得到的值。水平条表示从每条曲线计算的平均肺毛细血管PO₂。

Unfortunately, this approach, known as the Bohr integration procedure, was shown to be invalid when it was found that the fundamental assumption was untrue. The rate of transfer of oxygen is not proportional to the alveolar/ capillary Po2 gradient at any point along the capillary. It would no doubt be true if the transfer of oxygen were a purely physical process, but the rate of transfer is actually limited by the chemical combination of oxygen with haemoglobin, which is sufficiently slow to comprise a major part of the total resistance to transfer of oxygen.

不幸的是，已证明这种称为Bohr积分法无效，因为基本假设不成立。在毛细血管的任何一点上，O₂的弥散量与肺泡/毛细血管的PO₂梯度不成正比。如果O₂的弥散是一个纯粹的物理过程，这无疑是正确的，但弥散速度实际上受到O₂与血红蛋白的化学结合的限制，血红蛋白的化学结合速度非常慢，是O₂弥散总阻力的主要部分。

Studies in vitro of the rate of combination of oxygen with haemoglobin have shown that this is not directly proportional to the Po2 gradient, for two distinct reasons: 

体外氧与血红蛋白结合的速度研究表明，O2的弥散量与PO2梯度不成正比，原因有两条：

1. The combination of the fourth molecule of oxygen with the haemoglobin molecule (Hb4 (O2)3 1 O2  Hb4 (O2)4) [(O2)4)] has a much higher velocity constant than that of the combination of the other three molecules (page 144).

1. 第四个氧分子与血红蛋白分子结合（Hb₄（O₂）₃+O₂⥨Hb₄（O₂）₄[（O₂）₄]比其他三个分子的结合具有更高的速度常数（第144页）。

 2. As the capillary oxygen saturation rises, the number of molecules of reduced haemoglobin diminishes, and the velocity of the forward reaction must therefore diminish by the law of mass action. This depends on the haemoglobin dissociation curve, and is therefore not a simple exponential function of the actual Po2 of the blood.

2.随着毛细血管血氧饱和度的升高，还原血红蛋白的分子数量减少，因此根据质量作用定律（译者注：即抗原和抗体或受体和配体的反应达到稳定时，游离反应物的结合速度等于结合物分解的速度），正向反应的速度必须降低。正向反应速度取决于血红蛋白离解曲线，因此不是实际血液PO2的简单指数函数。

When these two factors are combined it is found that the resistance to diffusion because of chemical combination of oxygen within the RBC is fairly constant up to a saturation of about 80% (Po2 5 6 kPa or 45 mmHg). Thereafter it falls very rapidly to become zero at full saturation. In view of these findings the Bohr integration procedure was elaborated to allow for changes in the rate of combination of haemoglobin with oxygen.9 Assuming traditional values for the alveolar/end-capillary Po2 difference, the resulting curve lies well to the left of the original Bohr curve, as shown by the continuous red curve in Figure 8.2, A. This indicated a mean pulmonary capillary Po2 greater than had previously been believed, and therefore an oxygen-diffusing capacity that was substantially greater than the accepted value. The situation is actually more complicated still, as quick-frozen sections of lung show that the colour of haemoglobin begins to alter to the red colour of oxyhaemoglobin within the pulmonary arterioles before the blood has even entered the pulmonary capillaries. Furthermore, pulmonary capillaries do not cross only a single alveolus, but may pass over three or more.

当将这两个因素都考虑时，发现由于红细胞内氧的化学结合而产生的弥散阻力在氧饱和度上升至80%（PO₂ 56 kPa或45 mmHg）前相当稳定，从氧饱和度80%上升至100%时，氧弥散阻力迅速下降，到完全饱和时下降到零。鉴于这些变化，Bohr积分法考虑了血红蛋白与O₂结合速率的变化。⁹假设肺泡/末梢毛细血管PO₂差值为 traditional values，那所得Bohr曲线位于原始Bohr曲线的左侧，如图8.2，A中的连续红色曲线所示。这表明实际上平均肺毛细血管PO₂大于先前认为的值，因此氧的弥散量明显高于以前公认值。事实上情况更为复杂，肺部的速冻切片显示，在血液进入肺动脉之前，肺小动脉血红蛋白的颜色就开始在变为氧合血红蛋白的红色。此外，肺毛细血管不仅穿过一个肺泡，还可以穿过三个或更多个肺泡。

traditional values？怎么理解？最初的那个值？和过去一样的假定值？谢谢