Table 1.

Diagrams and brief descriptions of the shapes identified for tracheal ring classification

Assigned code	Tracheal ring shape	Description of ring
A		A singular band of tracheal cartilage resembling a ring throughout with parallel borders
B		A straight band of tracheal cartilage on the left half of the ring, and a split into two distinct bands at the right end
C		A straight band of tracheal cartilage on the right half of the ring, and a split into two distinct bands at the left end
D		Two singular rings of tracheal cartilage connected by a band of cartilage directed infero-medially from the right end of the proximal ring
E		Two singular rings of tracheal cartilage connected by a band of cartilage directed infero-medially from the left end of the proximal ring
F		A thick ring of tracheal cartilage with two distinct bands on both right and left ends
G		A thick ring of tracheal cartilage with a slit in the centre
H		A band of tracheal cartilage that resembles an upright pentagon in shape with an apex in the centre of the superior border
I		A band of tracheal cartilage that resembles an inverted pentagon in shape with an apex in the centre of the inferior border
J		A triangular piece of cartilage on the left side that did not extend beyond the tracheal midline. Connective tissue occupied the rest of the layer
K		A triangular piece of tracheal cartilage on the right side that did not extend beyond the tracheal midline. Connective tissue occupied the rest of the layer
L	Other	A ring shape which does not conform to the aforementioned descriptions or is a combination of one or more of the ring types