Predictive criteria for difficult tracheal intubation in a Moroccan population: A prospective observational study

Background: Difficult tracheal intubation (DTI) may be a major cause of morbidity and mortality if not anticipated. Pre-anesthesia airway risk assessment is a must for safety reasons. The aim of this study is to analyze the clinical predictive criteria for DTI with particular focus on the Mallampati score in the supine and sitting positions. Methods: This is a 6-month prospective observational study including all surgical adult patients requiring oro-tracheal intubation and not relevant to an indication for fibroscopic intubation nor urgent surgery (N = 500). DTI predictive criteria, composite scores, mask ventilation, laryngoscopy, and glottic catheterization were collected. Primary outcome was the ability of the collected criteria to predict DTI. Secondary outcome was the comparison of the Mallampatti score in the sitting vs. supine position to predict DTI using Cohen's kappa non-parametric test. Results: Mean age was 46.5 years. 10 % had diabetes. The incidence of DTI was 26 %. Six predictive factors for DTI were identified in multivariate analysis (p < 0.05): body mass index greater than 30 kg/m(2), mouth opening <3.5 cm, thyromental distance <6.5 cm, grades III and IV of Mallampati sitting and supine scores and Cormack and Lehane score IV. Mallampati supine score outperformed Mallampati sitting score in predicting the risk of difficult intubation, with respective ROCs at 0.898 (IC95 % 0.857-0.938) vs 0.751 (IC95 % 0.678-0.824). Conclusions: Incidence of DTI was higher in our population, probably related to our specific context of care. Predictive factors of DTI are consistent with previous studies while composite scores are not conclusive. The supine Mallampati performed better than sitting Mallampati in predicting DTI and may be reliable pre-operatively to assess the airway in patients unable to sit.