Effect of Altitude on Alveolar Oxygen Pressure

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This Demonstration shows the effects of changes in altitude on alveolar oxygen pressure using the alveolar gas equation: , where is the alveolar partial pressure in mmHg, is the fraction of inspired oxygen, and is the vapor pressure of water at 37 °C, 47 mmHg.


As altitude increases, the atmospheric pressure decreases. This causes a decrease in partial pressure of oxygen in the arteries. The slider for changes the percentage of oxygen in the air from 21% (the normal fraction) to 50% (the maximum amount that avoids lung toxicity). For simplicity, , the partial pressure of carbon dioxide, is set to 35 mmHg as a reasonable average value.

The changes in partial pressure of oxygen are shown numerically and graphically. The lines on the graph represent the altitudes at four different locations and the corresponding changes in as is increased. The visual model shows an increase in oxygen molecules as is increased, as well as a color gradient in the blood cells to represent the level of oxygenation in the blood.


Contributed by: Natalie Gurevich and Kaitlyn Kuder (December 2017)
Open content licensed under CC BY-NC-SA




[1] University of Colorado. "Rules on Oxygen Therapy." (Dec 4, 2017) www.ucdenver.edu/academics/colleges/medicalschool/departments/medicine/intmed/imrp/CURRICULUM/Documents/Oxygenation%20 and %20 oxygen %20 therapy.pdf.

[2] D. Curran-Everett, "A Classic Learning Opportunity from Fenn, Rahn, and Otis (1946): The Alveolar Gas Equation," Advances in Physiology Education, 30(2), 2006 pp. 58–62. doi:10.1152/advan.00076.2005.

[3] J. Conkin, "Equivalent Air Altitude and the Alveolar Gas Equation," Aerospace Medicine and Human Performance, 87(1), 2016 pp. 61–64. doi:10.3357/AMHP.4421.2016.

[4] S. Martin and B. Maury, "Modeling of the Oxygen Transfer in the Respiratory Process," ESAIM: Mathematical Modelling and Numerical Analysis, 47(4), 2013 pp. 935–960. doi:10.1051/m2an/2012052.

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