The trachea (windpipe) is made up of cartilage, which is 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.