Why do people with copd (emphysema and chronic bronchitis) need to have oxygen tubes all the time?

The primary function of the lungs is to exchange carbon dioxide with oxygen. This allows our bodies to function, that is to live. We get our oxygen normally from the air but air does not actually contain that much all the other stuff is expelled when we breath out. In order for out body to work it needs a minimum amount of oxygen. in COPD the lungs do not work as well as they should and as such for each breath taken not enough oxygen is exchange, this ultimately will lead to death but more often reduce bodily function that is for example the inability to move about. The oxygen is pure from a presurised bottle basicly this increases the amount of oxygen in lungs which stops the COPD patient being short of oxygen, basically it keeps them able to move about and ultimately live. However the long term use of pure oxygen can harm the lungs so ultimately it is not a cure it can only help to keep someone going for a time. The best thing to do is to not get COPD which is most often caused by smoking.