Incidence of Unanticipated Difficult Airway Using an Objective Airway Score Versus a Standard Clinical Airway Assessment, The DIFFICAIR Trial - A Cluster-randomized Clinical Trial on 28 Anaesthesia Departments With 70,000 Patients Registered in the Danish Anaesthesia Database

The full trial protocol is published in Trials (2013) Volume: 14, Issue: 1, Pages: 347 ISSN: 1745-6215 DOI: 10.1186/1745-6215-14-347 PubMed: 24152537 http://www.trialsjournal.com/content/14/1/347/abstract

Detailed statistical analysis plan for the difficult airway management (DIFFICAIR) trial:

Introduction The difficult airway management trial (DIFFICAIR) is a stratified, parallel group, cluster (cluster = department) randomized and multicentre trial involving 28 departments of anaesthesia in Denmark. The DIFFICAIR trial compares the effect of two regimens of preoperative airway assessment on the frequency of unanticipated difficult airway management.

Prediction of difficult airway management remains a pivotal challenge in anaesthesia. Difficult tracheal intubation and difficult mask ventilation may cause serious patient complications [1-6]. By allocating experienced personnel and relevant equipment, better prediction of difficult airway management may reduce complications and thereby associated morbidity and mortality. There is no single predictor that is sufficiently valid in predicting difficult tracheal intubation[7-12]. However, several studies show that by combining multiple predictors of difficult tracheal intubation, the positive and the negative predictive value of the assessment increases[12]. In Denmark as well as internationally, there is no clear recommendation on how to perform airway assessment. Consequently, airway assessment in Denmark is based exclusively on the individual anaesthesiologist's preoperative clinical assessment. It is poorly documented how accurately this preoperative clinical assessment predicts actual airway management conditions.

The "Simplified Airway Risk Index" (SARI)[13] is based on a multivariate model for airway assessment described by El-Ganzouri and colleagues enabling an estimation of the likelihood of a difficult direct laryngoscopy. The SARI contains seven individual predictors for a difficult direct laryngoscopy, each given a weighted score of 0-1 or 0-2. A summarized value of the SARI score > 3 indicate that a future direct laryngoscopy will be difficult. It is unknown, whether the SARI score predicts difficult intubation better or worse than a clinical assessment. The rationale for this trial was to prospectively compare the effect of the SARI with an unspecified clinical airway assessment on the frequency of unanticipated difficult airway management.