What does having a barrel chest mean?

Lung disease: Barrel chest is a deformity of the chest wall that develops in response to chronic over-inflated lungs. This is typically seen in patients with long standing, advanced emphysema, which is usually caused by smoking tobacco.

Shape of chest: A "barrel chest" is the change in shape of a chest due to emphysema. When the lungs get destroyed from smoking (most often), it is hard to blow the air out of the lungs, which causes the lungs to get bigger with the trapped air. Thus, the chest changes shape to look like a "barrel.".

Diameter...: A barrel chest means that there is an increased diameter of the chest wall. COPD patients can develop a barrel chest over time.