Figure 1. The ultrathin-walled two-stage endotracheal tube. The approximate midsection of the ETT labeled "larynx" is positioned at the level of the glottic opening. Hence, some of the "gills" will be above and some will be below the level of the vocal cords; the optimal position is midway. (Insert) Gills that pass across the glottic opening commonly are somewhat folded.