A person with emphysema often needs to be given supplemental oxygen, but why is it important?

Oxygen: At sea level the atmosphere has 21% oxygen. At higher elevations this can be less. Of that we breath it into our body and the oxygen gets replaced in our blood from carbon dioxide we breath out. So in patients with underlying heart or lung problems, in order to make sure they get enough (as measured by oxygen level at a fingertip), we need to give them higher % of inspired oxygen through machine.

You need it!: Emphysema is a disease of lung tissue destruction, so there is less surface area in the lung to get oxygen from the air. Supplemental oxygen delivers a higher consentration of oxygen so that the damage tissue can get oxygen into the blood. Without oxygen, your organs, especially your brain, don't function well... And in the long run you will die younger and feeling worse than if you wore it.

O2 is good.: Long term oxygen therapy has been shown in some trials to improve mortality. It has also been shown in other trials to improve quality of life, reduce depression, improve cognitive function, improve exercise capacity, and reduce frequency of hospitalization.