This is a medical question of type : information 
 What is (are) Oxygen Therapy ? 
 Oxygen therapy is a treatment that provides you with extra oxygen, a gas that your body needs to work well. Normally, your lungs absorb oxygen from the air. However, some diseases and conditions can prevent you from getting enough oxygen.
                
Oxygen therapy may help you function better and be more active. Oxygen is supplied in a metal cylinder or other container. It flows through a tube and is delivered to your lungs in one of the following ways:
                
Through a nasal cannula, which consists of two small plastic tubes, or prongs, that are placed in both nostrils.
                
Through a face mask, which fits over your nose and mouth.
                
Through a small tube inserted into your windpipe through the front of your neck. Your doctor will use a needle or small incision (cut) to place the tube. Oxygen delivered this way is called transtracheal oxygen therapy.
                
Oxygen therapy can be done in a hospital, another medical setting, or at home. If you need oxygen therapy for a chronic (ongoing) disease or condition, you might receive home oxygen therapy.
                
Overview
                
To learn how oxygen therapy works, it helps to understand how your respiratory system works. This system is a group of organs and tissues that help you breathe. The respiratory system includes the airways and lungs.
                
The airways carry oxygen-rich air to your lungs. They also carry carbon dioxide (a waste gas) out of your lungs.
                
Air enters your body through your nose or mouth, which moistens and warms the air. The air then travels through your voice box and down your windpipe. The windpipe divides into two tubes called bronchi that enter your lungs.
                
Within your lungs, your bronchi branch into thousands of smaller, thinner tubes called bronchioles (BRONG-ke-ols). These tubes end in bunches of tiny round air sacs called alveoli (al-VEE-uhl-eye).
                
Each of the air sacs is covered in a mesh of tiny blood vessels called capillaries (KAP-ih-lare-ees). The capillaries connect to a network of arteries and veins that move blood throughout your body.
                
When air reaches the air sacs, the oxygen in the air passes through the air sac walls into the blood in the capillaries.
                
The oxygen-rich blood then travels to the heart through the pulmonary vein and its branches. The heart pumps the oxygen-rich blood to your organs. (For more information, go to the Health Topics How the Lungs Work article.)
                
Certain acute (short-term) and chronic (ongoing) diseases and conditions can affect the transfer of oxygen from the alveoli into the blood. Examples include pneumonia (nu-MO-ne-ah) and COPD (chronic obstructive pulmonary disease).
                
Your doctor will decide whether you need oxygen therapy based on the results of tests, such as an arterial blood gas test and a pulse oximetry test. These tests measure how much oxygen is in your blood. A low oxygen level is a sign that you need oxygen therapy.
                
Oxygen is considered a medicine, so your doctor must prescribe it.
                
Outlook
                
Oxygen therapy helps many people function better and be more active. It also may help:
                
Decrease shortness of breath and fatigue (tiredness)
                
Improve sleep in some people who have sleep-related breathing disorders
                
Increase the lifespan of some people who have COPD
                
Although you may need oxygen therapy long term, it doesn't have to limit your daily routine. Portable oxygen units can make it easier for you to move around and do many daily activities. Talk with your doctor if you have questions about whether certain activities are safe for you.
                
A home equipment provider will work with you to make sure you have the supplies and equipment you need. Trained staff also will show you how to use the equipment correctly and safely.
                
Oxygen therapy generally is safe, but it can pose a fire hazard. To use your oxygen safely, follow the instructions you receive from your home equipment provider.