and bottom to avoid confusion during emergency procedures moreover the square profile with flat top and bottom surfaces adapted to engage the cricothyroid membrane is more stable when disposed in position and is less likely to rotate in this regard the stability of the instrument in position is important because if a tracheal tube is not inserted into the cannula properly so that it goes down the trachea without irritating the internal membranes thereof unnecessary complications of the procedure can develop as clearly shown in fig2 the cannula 12 is disposed within the channel or cavity 27 formed within the cutting member 15 the channel may be partially or fully enclosed the cannula 12 comprises a housing 50 and a centering means 52 as can be clearly seen in fig6 the housing 50 has a rounded posterior portion designed to easily slide out between the blades 34 and 35 and to safely engage the posterior surface of the tracheal lumen 24 without causing any substantial injury or irritation thereto although the housing 50 is depicted herein having a rounded leading edge 54 any blunted surface will properly function for the instrument to avoid traumatizing the trachea on the sides of said housing 50 a handle is disposed to assist the user in removing the cannula 12 from the cutting member 15 in the preferred embodiment the handle comprises a pair of.