Dalton's law of partial pressures applies equally to birds and mammals so, as gas moves from the nostrils to the smallest gas diffusion airways, the sequential addition of water vapour and CO2, steadily reduce the partial pressure of O2 (PO2) within the gas mixture. At sea level, the final PO2, at the point of gas exchange, will be about 60 mm Hg less than the original PO2 within atmospheric air. As a result, the inspired PO2 is an inaccurate starting point for any model of oxygen transport. In humans, the interactions of gases at the point of diffusion, is described and quantified by the Alveolar Gas Equation (AGE). Its development during WW2, provided valuable insights into human gas exchange and also into the response to high altitude flight in pilots but, except for an earlier study of hypoxia in pigeons, the AGE is not mentioned in the avian literature. Even detailed models of oxygen transport in birds omit the effect of CO2 clearance on pulmonary oxygen transfer. This paper develops two related arguments concerning the application of the AGE to birds. The first is that avian blood gas predictions, based on the theory of serial multicapillary arterialization (MSA), are inaccurate because they do not account for the added partial pressure of diffused CO2. The second is that the primary adaptation to hypobaric hypoxia is the same for both classes and consists of defending PaO2 by reducing PaCO2 through increasing hyperventilation. Support for the first is demonstrated by comparing PaO2 made using the AGE, with published values from avian studies and also against values predicted by the theory of MSA. The second is illustrated by comparing the results of high altitude studies of both birds and humans. The application of the AGE to avian respiratory physiology would improve the predictive accuracy of models of the O2 cascade and would also provide better insights into the primary adaptation to high altitude flight.

中文翻译：

---

肺泡气体方程式：第二次世界大战对高空飞行飞行员进行研究的教训是否为鸟类适应高空飞行提供了见识？

道尔顿分压定律同样适用于鸟类和哺乳动物，因此，当气体从鼻孔移动到最小的气体扩散气道时，水蒸气和CO2的顺序添加会稳步降低混合气体中O2（PO2）的分压。在海平面上，在气体交换点的最终PO2将比大气中的原始PO2少约60 mm Hg。结果，灵感来源的PO2对于任何氧气传输模型都是不准确的起点。在人类中，通过肺泡气体方程（AGE）描述和量化了扩散点处气体的相互作用。它在第二次世界大战期间的发展，为人们进行气体交换以及飞行员对高空飞行的反应提供了宝贵的见解，但是，除了早期对鸽子缺氧的研究之外，禽类文献中未提及AGE。甚至鸟类中氧气运输的详细模型都忽略了CO2清除对肺部氧气转移的影响。本文提出了两个有关AGE应用于禽类的观点。首先是基于串行多毛细管动脉化（MSA）理论的禽血气预测是不准确的，因为它们没有考虑到扩散的CO2的增加的分压。第二个是，对低压缺氧的主要适应性在这两个类别中都是相同的，包括通过增加过度换气来减少PaCO2来防御PaO2。通过比较使用AGE制备的PaO2，禽类研究的公开值以及MSA理论预测的值，证明了对第一种方法的支持。通过比较鸟类和人类的高空研究结果来说明第二个问题。AGE在禽类呼吸生理学中的应用将提高O2级联模型的预测准确性，还将为对高海拔飞行的主要适应性提供更好的见解。