Identification of ideal preoperative predictors for difficult intubation

Background: Unexpected difficult intubation is probably the result of inadequate preoperative examination of airway and a lack of accurate predictive tests for difficult intubation. Preoperative evaluation forms basis to suspect and be prepared for a difficult airway situation. Aim: The aim of our study was to identify the ideal preoperative predictors of difficult intubation. Materials and Methods: It was a Prospective Observational study done on 350 patients in a community-based hospital. Preoperative airway assessment included: Mallampati Class (MC), Mouth opening (MO), Thyromental distance (TMD), Ability to prognath (AP) and Neck mobility and size (NM). Monitors were attached, anesthesia induced and laryngoscopy performed. Intubation Difficulty Scale (IDS) score was used to grade difficulty in intubation. Results: The overall incidence of Difficult Intubation was 24.6 %. A slight difficulty in 24% (IDS = 1-5) and moderate to major difficulty (IDS >5) in 0.6% cases was noted. Intubation was possible in all the patients. Mallampati class III & Mouth opening was less than 4 cm in about 6% cases and Thyromental distance less than 6 cm in 5.4%. 12.5% were unable to prognath and Neck mobility was restricted in 4.6% patients. Sensitivity and specificity of MC- 16.3 % and 97%, MO- 16.3% and 96.6%, TMD - 12.8% and 97%, AP - 33.3% and 93.9% , NM - 10.5% and 97.3%. Positive and Negative Predictive Values for MC, MO, TMD, AP and NM were 63.6% and 78%, 60.9% and 78%, 57.9 and 77.3 %, 62.8% and 81.9%, 56.3% and 76.9% respectively. Conclusion: We concluded that Mallampati grading and ability to prognath are the most important of the variables studied.