Oxygen Levels at Altitude

Although the percentage of oxygen in inspired air is constant at different altitudes, the fall in atmospheric pressure at higher altitude decreases the partial pressure of inspired oxygen and hence the driving pressure for gas exchange in the lungs. An ocean of air is present up to 9-10 000 m, where the troposphere ends and the stratosphere begins. The weight of air above us is responsible for the atmospheric pressure, which is normally about 100 kPa at sea level. This atmospheric pressure is the sum of the partial pressures of the constituent gases, oxygen and nitrogen, and also the partial pressure of water vapor (6.3 kPa at 37°C). As oxygen is 21% of dry air, the inspired oxygen pressure is 0.21×(100−6.3)=19.6 kPa at sea level.

Atmospheric pressure and inspired oxygen pressure fall roughly linearly with altitude to be 50% of the sea level value at 5500 m and only 30% of the sea level value at 8900 m (the height of the summit of Everest). A fall in inspired oxygen pressure reduces the driving pressure for gas exchange in the lungs and in turn produces a cascade of effects right down to the level of the mitochondria, the final destination of the oxygen.

Divider
RESOURCE: Altitude Air Pressure Calculator
Divider

 

Use the table below to see how the effective amount of oxygen in the air varies at different altitudes. Although air contains 20.9% oxygen at all altitudes, lower air pressure at high altitude makes it feel like there is a lower percentage of oxygen. The chart is based on the ideal gas law equation for pressure versus altitude (Barometric Formula), assuming a constant atmospheric temperature of 32 degrees Fahrenheit (0 Celsius), and 1 atmosphere pressure at sea level.

 

Altitude (feet) Altitude (meters) Effective Oxygen % Altitude Category Example
0 ft 0 m 20.9 % Low Sea Level
1,000 ft 305 m 20.1 % Low
2,000 ft 610 m 19.4 % Low
3,000 ft 914 m 18.6 % Medium
4,000 ft 1,219 m 17.9 % Medium
5,000 ft 1,524 m 17.3 % Medium Boulder, CO  (5328')
6,000 ft 1,829 m 16.6 % Medium Mt. Washington (6288')
7,000 ft 2,134 m 16.0 % Medium
8,000 ft 2,438 m 15.4 % High Aspen, CO  (8,000')
9,000 ft 2,743 m 14.8 % High
10,000 ft 3,048 m 14.3 % High
11,000 ft 3,353 m 13.7 % High Mt. Phillips  (11,711')
12,000 ft 3,658 m 13.2 % High Mt. Baldy  (12,441')
13,000 ft 3,962 m 12.7 % Very High
14,000 ft 4,267 m 12.3 % Very High Pikes Peak  (14,115')
15,000 ft 4,572 m 11.8 % Very High
16,000 ft 4,877 m 11.4 % Very High Mont Blanc  (15,781')
17,000 ft 5,182 m 11.0 % Very High
18,000 ft 5,486 m 10.5 % Extreme
19,000 ft 5,791 m 10.1 % Extreme Kilimanjaro  (19,341')
20,000 ft 6,096 m 9.7 % Extreme Denali  (20,308')
21,000 ft 6,401 m 9.4 % Extreme
22,000 ft 6,706 m 9.0 % Extreme
23,000 ft 7,010 m 8.7 % Extreme Aconcagua  (22,841')
24,000 ft 7,315 m 8.4 % Extreme
25,000 ft 7,620 m 8.1 % Extreme
26,000 ft 7,925 m 7.8 % Ultra
27,000 ft 8,230 m 7.5 % Ultra
28,000 ft 8,534 m 7.2 % Ultra K2  (28, 251')
29,000 ft 8,839 m 6.9 % Ultra Mt. Everest  (29,029')

 

Sources:

BMJ. 1998 Oct 17; 317(7165): 1063–1066.
doi: 10.1136/bmj.317.7165.1063
PMCID: PMC1114067
PMID: 9774298
ABC of oxygen

USGS Map Point Elevation Query Service
https://nationalmap.gov/epqs/

 

 


Check out our First Aid Shop!
Visit the First Aid Gear Shop

 

Our Courses

Wilderness First Aid

Wilderness First Responder

Stop The Bleed

Adult + Child CPR-AED

Standard First Aid



 

Visit the First Aid Gear Shop


2 thoughts on “Oxygen Levels at High Altitudes”


Want to Sponsor a Wilderness Medicine Course @ Your Location?LEARN MORE
+