The term "barrel chest" describes a rounded, bulging chest that resembles the shape of a barrel. Barrel chest isn't a disease, but it may indicate an underlying condition.
Barrel chest most commonly relates to osteoarthritis as you age. Arthritis can stiffen the joints where the ribs attach to the spine, not unlike what happens to aging finger joints. The ribs become fixed in their most expanded position, causing the appearance of a barrel chest.
Some people who have chronic obstructive pulmonary disease — such as emphysema — develop a slight barrel chest in the later stages of the disease. It occurs because the lungs are chronically overinflated with air, so the rib cage stays partially expanded all the time. This makes breathing less efficient and aggravates shortness of breath.
Generally, barrel chest itself isn't treated, but when the cause is severe emphysema, the underlying disease is treated