The two curves theory was first proposed by K Greenland in 2010 to explain what’s occurring when we place patients in the sniffing position for direct laryngoscopy, its true value is in improving our understand of the path we take to access the trachea during video laryngoscopy.

Mathematically defined as a bezier spline, it takes a serpentine path that can be divided into a primary (oro-pharyngeal) and secondary curve (pharyngo- glotto-tracheal). These curves are in opposite directions, and the point where these curves meet (the point of inflection) is contained within a space somewhere between the epiglottis to the glottis.