A sheath for an endotracheal intubation device includes an elongate flexible portion defining a closed conduit and an adjacent open channel defined by opposing lips for releasably retaining an endotracheal tube, and a rigid portion extending from a distal end of the flexible portion, the flexible portion including a gap in one of the lips adjacent the rigid portion to expose an edge of the rigid portion, the gap allowing the endotracheal tube to be pinched between the edge of the rigid portion and a lip of the flexible portion to enhance retention of the tube when an articulated arm disposed in the closed conduit is curved, and facilitate release of the tube when the arm is not curved.