When performing VL it seems intuitive that bigger is better on the screen. The 2 curve theory (referred to as 2 C's in video) refers to 2 opposing paths that the ETT must pass, first the oral-pharygeal-laryngeal and the second pharyngeal-layngeal-tracheal (described by Greanland). The problem is when you are too close and posterior to the epiglottis several things happen: 1. The blade tip may deflect the larynx anterior making the ETT trajectory through inlet more perpendicular to the long axis of the trachea making it more likely to hit the anterior tracheal wall. 2. The ETT will have to travel a more acute posterior to anterior direction. 3 There is less space to maneuver the ETT in view. 4. The opposing curves are in general more acute. With the blade tip in the vallecula the Glidescope is oriented in a more favourable lie with the blade in-line with the long axis of the trachea. This makes the overlapping portion of the 2 curves less acute and allows the ETT enter the trachea parallel to as opposed to more perpendicular to its long axis. It also allows more room to manipulate the ETT in view. So don't get too close. Place the blade tip in the vallecula and ensure that the image of the glottic inlet occupies the top half or less of the screen. Try it, you'll like it!
