Correlation of Neck Dimensions of Airway Evaluation

The goal of this observational study is to evaluate thyromental distance (TMD) and mandibular triangle perpendicular length (MTPL); to know which correlates better with the incisor vallecula distance (IVD). Based on the direction and strength of the correlation measure, a multiple regression equation can then be created to first predict the IVD with external linear measure, and second, based on IVD length prediction, the appropriate laryngoscope blade size can be ascertained.

Inclusion Criteria: 1. Age 18-65 years 2. Males and females 3. ASA (American Society of Anaesthesiologists) physical status I and II 4. Patients scheduled for elective surgery with controlled ventilation through orotracheal tube conduit Exclusion Criteria: 1. Smokers (those who have smoked ≥100 cigarettes in their lifetime), chewing tobacco dependence or substance abuse 2. Submucous fibrosis: progressive fibrosis of the submucosal tissue leading to rigidity, relative trismus, and progressive decrease of mouth opening 3. Anticipated difficult airway 4. Patients requiring intubation with MacIntosh blade #4 or #5 5. Dental issues: * missing tooth (upper/lower incisors, upper/lower premolar) * crowded dentition: - irregular, misaligned, or overlapping teeth within a relatively small oral cavity * presence of artificial teeth and/or dental implants • Mandible/mandibular structure related issues: * Retrognathia: - posterior displacement of the mandible relative to the maxilla or cranial base * Prognathia: - anterior displacement of the mandible relative to the maxilla or cranial base 6. Emergency Surgery 7. Those requiring urgent rapid-sequence intubation due to the presence of a full-stomach status secondary to gastro-esophageal reflux disease, diaphragmatic hernia, among others. 8. Refusal to informed consent