Did you know that the concentration of oxygen in the atmosphere remains constant at 20.95% up to 100,000 feet.
At sea level, this translates to an oxygen partial pressure of 212 mbar, which is 20.95% of the standard atmospheric pressure (1013 mbar) according to Dalton’s law.
As you ascend, the partial pressure of gases, including oxygen, decreases due to lower atmospheric pressure. For instance, at 40,000 feet, the oxygen partial pressure drops to just 39 mbar.
That’s far too low to support human metabolism!
One way to counteract low oxygen levels at high altitudes is by increasing oxygen concentration in the air we breathe.
At 40,000 feet, inhaling pure oxygen (100% concentration) can raise the partial pressure to a maximum of 188 mbar.
Another effective method for preventing hypoxia is positive pressure breathing.
Modern crew oxygen masks deliver pure oxygen under pressure, increasing the oxygen partial pressure by an additional 20-30 mbar for short durations.
To achieve conditions equivalent to those at sea level while at 40,000 ft, we need to breathe 100% oxygen combined with positive pressure breathing.
However, positive pressure breathing requires training and can be tiring, which is why it has primarily been reserved for flight crew in emergencies and only for brief periods.
The combination of increased oxygen concentration and positive pressure breathing is crucial for safety at high altitudes.
Author – Arjun Singh
