Fig. 1. The four procedures. (1 ) Simple direct laryngoscopy with no assistance. (2 ) Direct laryngoscopy with mandibular advancement. (3 ) Direct laryngoscopy with BURP maneuver. (4 ) Direct laryngoscopy both with mandibular advancement and with BURP maneuver. The procedures were performed with one laryngoscopist and two assistants. A cameraperson who videotapes the laryngeal aperture is not shown in the figure.