If you have COPD and you are considering travel that specifically involves airline travel, there are some facts that you should know. If you currently use oxygen, then your needs may change when you travel by air. How you manage the need for oxygen (or not) once airborne depends on a few factors.
In order to understand what happens in higher altitudes, you have to first understand how oxygen is obtained from the environment. We breathe air in, and when it reaches the lungs (alveolar) air sacs, it has to cross over to the blood vessels that surround the sacs. Then the oxygen is carried by red blood cells, so that it can be used for energy by all the organs in your body. Oxygen, like all gases, will travel in the direction of the highest pressure to lower pressure.
At sea level, the air pressure is 760 mm of mercury (mmHg). Since the air you inhale contains 21 percent oxygen, the pressure of oxygen in the air is 159 mmHg. The partial pressure of the blood in your body that is carried by the veins into the lungs is only 40-50mmHg. That means that there is enough of a differential in the pressures to allow oxygen to naturally move from the lungs into the bloodstream, so that the arteries that leave the heart are carrying oxygenated blood.
This scenario just described is what occ