“The term ‘best effort’ is used by the Vortex Approach to describe the circumstance in which all viable strategies to facilitate success at entering the Green Zone via a given lifeline have been implemented. Up to three attempts (+/- a ‘gamechanger’ – see below), each incorporating additional optimisations that have not previously been implemented, are permitted to complete a best effort. The specific optimisations employed and the number of attempts that are appropriate to achieve a best effort are context dependent decisions, to be made by the airway operator within the confines of the principles set out by the Vortex Approach. 

If following a completed best effort at a particular lifeline, alveolar oxygen delivery has not been achieved, then no further attempts at that lifeline should occur. Efforts should instead focus on establishing alveolar oxygen delivery via an alternate lifeline – or on initiating Neck Rescue if all three lifelines have been unsuccessful.  

–The Vortex Approach