The trachea (windpipe) is made up of cartilage, which are also called tracheal rings. Normally, tracheal rings are “C” shaped. Complete tracheal rings are “O” shaped. The “O” shaped rings are always smaller than the normal “C” shape.
Complete tracheal rings are a rare condition present at birth. It is usually associated with other vascular (blood vessel), heart, or lung abnormalities