Query re: Partial pressures of O2 in high vs low pressure environments

In summary, the partial pressure of oxygen (O2) is significantly higher in high pressure environments compared to low pressure environments. This is due to the fact that the total number of gas molecules in a given volume is greater in high pressure environments, resulting in a higher concentration of O2 molecules. This can have significant impacts on physiological processes, as the body must adjust to the varying levels of O2 in different environments. Additionally, high pressure environments can lead to increased levels of dissolved O2 in liquids, such as blood, which can also affect the body's functioning. Overall, understanding the differences in partial pressures of O2 in high and low pressure environments is important for understanding the effects of these environments on both living organisms and industrial processes.
  • #1
Thunderhoof
3
0
TL;DR Summary
Why are people climbing Everest on 100% oxygen hypoxic?
Hi, I'm currently learning to scuba dive and we use a very simple way to calculate the partial pressure of oxygen at depth to avoid oxygen toxicity, for example at sea level of 1 atm and 21% O2 concentration the partial pressure is calculated to be 0.21, and at 60m (pressure increases by 1 atm for every 10m of depth) that's 7 atm x 21% which is 1.47 which is around the cut off point for O2 toxicity, at which point we start needing to breathe hypoxic gas mixtures to maintain a safe partial pressure of oxygen. For reference the world record dive of 534m was achieved with the diver breathing a mixture of 49% hydrogen, 50.2% helium and 0.8% oxygen to maintain a safe partial pressure of oxygen.

If this is the case for high pressure environments why does the same not seem to hold true for low pressure environments like the top of Everest? If the partial pressure of 100% oxygen at 1 atm is equal to 1.0, why is the partial pressure of 100% oxygen at the 0.35 atm on Everest not equal to 0.35 and is instead hypoxic? I'd appreciate any insight on this.
 
Biology news on Phys.org
  • #2
The partial pressure of 100% oxygen at 0.35 atm is 0.35 atm. Why do you think it is hypoxic?
 
  • #3
There seem to be a significant number of reports of hypoxia from people climbing Everest on 100% oxygen, but I suppose this could be because of a limited flow rate I suppose compared to the full flow rate used in diving, or perhaps other physiological issues resulting from the low pressure atmosphere.
 
  • #4
Could you link to these reports?
I don't know but suppose they don't use regulators like in SCUBA to equalize pressure of the flowing gas to ambient pressure. Perhaps, a manual flow control instead. (?)
 
  • #5
Reading this article seems to explain the hypoxia.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1114067/

"However, it is difficult and expensive to arrange oxygen supplies so flow rates are kept low. The oxygen is used when sleeping, normally at 1-2 l/min via a face mask, and when climbing above 8000 m, normally 2-3 l/min."

Compared to 15-20 l/min when diving a climber would be getting substantially less oxygen into their body even at 100% vs 20%.
 

1. How does the partial pressure of oxygen change with altitude?

As altitude increases, the total atmospheric pressure decreases, which in turn lowers the partial pressure of oxygen. This is because the fraction of oxygen in the atmosphere (approximately 21%) remains constant, but the total pressure it is a part of decreases with altitude. At higher altitudes, the lower partial pressure of oxygen can make it harder to breathe and adequately supply oxygen to the body.

2. What is the impact of high altitude on the body due to changes in oxygen partial pressures?

At high altitudes, the reduced partial pressure of oxygen can lead to a condition known as hypoxia, where insufficient oxygen reaches the tissues. Initially, this can cause symptoms like headaches, dizziness, and shortness of breath. Prolonged exposure without adequate acclimatization can lead to more severe health issues, such as altitude sickness, high altitude pulmonary edema (HAPE), or high altitude cerebral edema (HACE).

3. How do low pressure environments, like those found underwater, affect oxygen partial pressures?

Underwater environments, especially at significant depths, involve increased pressures, which actually raise the partial pressures of gases, including oxygen. While this might seem beneficial, breathing oxygen at a high partial pressure can lead to oxygen toxicity, a condition that can cause lung damage, central nervous system issues, and other serious health effects.

4. What adjustments are necessary for breathing apparatus in high versus low pressure environments?

In high altitude environments, supplemental oxygen is often required to compensate for the lower oxygen availability. This equipment needs to be capable of delivering higher oxygen flow to match the body's needs. Conversely, in deep-sea diving or other high-pressure environments, the breathing gas mix must be carefully controlled to avoid oxygen toxicity; often, gases like helium are added to dilute the oxygen and nitrogen content to safer levels.

5. How is the safe level of oxygen partial pressure determined for different environments?

Safe levels of oxygen partial pressure are determined based on the environmental conditions and human physiological limits. Generally, an oxygen partial pressure of about 160 mmHg is considered safe and effective at sea level. For high altitude environments, supplemental oxygen might be required to maintain safe levels, while in high pressure underwater environments, the partial pressure of oxygen must be carefully managed to avoid exceeding safe limits, typically kept below 1.6 ATA (atmospheres absolute) to prevent toxicity.

Hot Threads

Recent Insights

Back
Top