Hyperbaric oxygen therapy is sometimes called "breathing-under-water." Oxygen is pumped into a chamber where a person spends an hour or more breathing pure oxygen. Oxygen under pressure increases the amount that is absorbed by the body.

The result is that more oxygen is available to the body cells for cellular respiration. For instance, when a person goes swimming in a pool, he or she breathes more deeply than usual.

This is because there is more Hyperbaric Oxygen Therapy Chamber in the water than in the air. The water is more oxygen-rich than the air. Therefore, the amount of oxygen the person absorbs during the swim increases, and the blood becomes more oxygenated.

Similarly, breathing in a pressurized chamber containing oxygen raises the level of oxygen in the blood. In some cases, people may have to breathe pure oxygen for several hours before undergoing hyperbaric oxygen therapy. This can be helpful when someone has a condition that affects his or her lungs.

For example, if someone has emphysema, a condition in which air sacs in the lungs enlarge, there may be a risk of developing a pneumothorax. Pneumothoraces are pockets of air that develop inside the chest wall. If a person develops a pneumothorax, he or she will be unable to breathe easily.