Is barrel chest a protruding sternum?

Not necessarily: A barrel chest commonly refers to the changes that occur from copd. A protruding chest is a description ofchanges to the sternum also sometimes referred to as pidgeon chest or pectus carnatum.

Not exactly: Appropriately, the chest wall deformity is called pectus carinatum. Another term is pigeon chest. Barrel chest is usually used to describe a patient with copd/emphysema in whom the chest is larger in all dimensions.