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Why do I need to wear oxygen?

As PAH progresses, the exchange of oxygen between the air and the blood is compromised (see pathophysiology section). As discussed previously, oxygen travels from the airways of the lungs down to the alveoli, where it crosses a membrane and enters the blood where it is carried by red blood cells to the rest of the body (again see prior sections). Oxygen is the fuel that all the cells in your body (including your brain, your muscles, your heart, etc.) consume in order to do their normal function.

In PAH, the process of transferring oxygen across the membranes separating the alveoli and the capillaries is compromised and we call this a diffusion impairment. In PAH, there are also fewer capillaries than normal, and therefore fewer opportunities for oxygen to make it into the bloodstream.

Wearing supplemental oxygen increases the concentration of oxygen in the air you are breathing. Normally in the air around us, there is 21% oxygen (the rest is mainly nitrogen and other trace amounts of different gases). By wearing supplemental oxygen, you can increase the percentage of oxygen that you are breathing. Although it is not exact, breathing 2 L oxygen by nasal cannalae probably increases the oxygen percentage that you are breathing to about 23-25%. This increased concentration then allows more oxygen to enter the bloodstream, in an effort normalize the oxygen content of your blood. Since oxygen is required for body to create energy, it is vital to all aspects of functioning. Therefore, decreased oxygen levels in your blood will cause various symptoms including fatigue, lightheadedness, chest discomfort and shortness of breath. Normalizing your oxygen level can improve those symptoms.

In addition, the natural response of pulmonary arteries to low oxygen levels is to constrict (hypoxic pulmonary vasoconstriction). In the setting of existing PAH, this vasoconstriction can lead to a further increase in already elevated PA pressures. Therefore, keeping oxygen levels close to normal range will help prevent this hypoxic vasoconstriction.

Your medical team would not prescribe oxygen unless your blood level of oxygen (your oxygen saturation or "O2 Sat") was dangerously low. It is very important that you use your oxygen as prescribed in order to keep your body healthy. Different PAH patients need to wear oxygen in different situations. Some PAH patients only need to wear oxygen at night (when we all breathe a little less than we do when we are awake), and you may undergo a test called "overnight oximetry" to check how low your oxygen level falls when you sleep. Other PAH patients may only require oxygen when they exert themselves, and the tests to determine this include "exercise oximetry" which involves measurement of oxygen saturations during a six minute walk test or cardiopulmonary exercise test. Some PAH patients have low oxygen saturations even when they are sitting or standing still, and these patients will need to wear oxygen all the time. Your medical team will determine whether you need oxygen and the situations - sleep, exercise, or all activities - in which you need to use it.