Figure 1: Schematic representation of the trachea showing where the inner transverse diameter (ITD), outer transverse diameter (OTD), inner vertical diameter (IVD), and outer vertical diameter (OVD) are. The thickness of the cartilaginous wall was measured on the dorsal, ventral, and lateral aspects as dorsal wall thickness (DWT), ventral wall thickness (VWT), and lateral wall thickness (LWT), respectively, were measured.