Oxygen therapy is used to treat low blood oxygen levels in people who have chronic (long-term) or acute (shorter-term but serious) health conditions that decrease the levels of oxygen in their blood. Oxygen is vital to the way the body works, because it interacts with food to produce energy that cells use as fuel. When 100% oxygen is given to people who have low blood oxygen levels, it increases the levels of oxygen in their bloodstreams. Raising the levels of oxygen in the blood to healthy levels helps to relieve symptoms caused by low blood oxygen levels, such as shortness of breath, fatigue and irritability. Oxygen therapy also can take strain off your heart, because it won't have to work so hard to circulate oxygen to your body.