 Because the airway of a child is narrow , a small amount of glottic or tracheal swelling can produce critical obstruction . Inserting a tube that is too large relative to the diameter of the trachea can cause swelling . Conversely , inserting a tube that is too small can result in inability to achieve effective positive pressure ventilation due to retrograde escape of gas through the glottis and out the mouth and nose ( often referred to as a " leak " around the tube ) . An excessive leak can usually be corrected by inserting a larger tube or a cuffed tube . 
