[Algorithm for securing an unexpected difficult airway : User analysis on a simulator]

Critical incidents in difficult airway management are still a main contributory factor for perioperative morbidity and mortality. Many national associations have developed algorithms for management of these time critical events. For implementation of these algorithms the provision of technical requirements and procedure-related training are essential. Severe airway incidents are rare events and clinical experience of the individual operators is limited; therefore, simulation is an adequate instrument for training and evaluating difficult airway algorithms.

The aim of this observational study was to evaluate the application of the institutional difficult airway algorithm among anesthetists.

After ethics committee approval, anesthetists were observed while treating a "cannot intubate" (CI) and a "cannot intubate, cannot ventilate" (CICV) situation in the institutional simulation center. As leader of a supportive team the participants had to deal with an unexpected difficult airway after induction of anesthesia in a patient simulator. The following data were recorded: sequence of the applied airway instruments, time to ventilation after establishing a secured airway using any instrument in the CI situation and time to ventilation via cricothyrotomy in the CICV situation. Conformity to the algorithm was defined by the sequence of the applied instruments. Analysis comprised conformity to the algorithm, non-parametric tests for time to ventilation and differences between junior and senior anesthetists.

Out of 50 participants 45 were analyzed in the CI situation. In this situation 93% of the participants acted in conformity with the algorithm. In 62% the airway was secured by flexible intubation endoscopy, in 38% with another device. Data from 46 participants were analyzed in the CICV situation. In this situation 91% acted in conformity with the algorithm. The last device used prior to the decision for cricothyrotomy was flexible intubation endoscopy in 39%, a laryngeal mask in 22% and other instruments in 39%. Of the 50 participants 38 had already been institutionally trained in difficult airway management during the previous 2 years. For cricothyrotomy the participants needed a median time of 63 s and there was no difference between junior and senior anesthetists (p = 0.46). The cricothyrotomy was performed faster using a surgical approach than a transtracheal puncture approach using a Melker emergency cricothyrotomy set (52 s vs. 73 s, p = 0.014).

The conformity to the algorithm of over 90% indicates a good training level of the participants concerning the difficult airway algorithm. In the observed sample flexible intubation endoscopy tended to be of high significance even in the unanticipated difficult airway. Cricothyrotomy was performed faster surgically than by the use of the transtracheal puncture approach, while no differences between junior and senior anesthetists were observed. For the successful management of an unexpected difficult airway, specific training of these special and rare events is crucial. A standardized provision of special airway instruments stored in a special trolley and frequent application of this trolley in the clinical routine is recommended.