Study of Correlation between Airway Assessment Parameters and Intubating Success with Intubating Laryngeal Mask Airway using PVC Endotracheal Tube – A Prospective Open Label Observational Study

Background and Aims: Evidence is limited regarding the correlation of airway assessment parameters with success rate of intubation with Intubating laryngeal mask airway (ILMA). Aim was to assess the correlation between airway parameters and success rate of blind intubation with conventional polyvinyl chloride (PVC) tube using ILMA. Methods: After ethical clearance and informed consent, 200 patients undergoing elective surgical procedures under general anaesthesia were enrolled. Mallapatti class, upper lip bite test (ULBT) grade, thyromental distance (cm), mouth opening (cm), neck circumference were noted. Anaesthesia regimen was standardized, Cormack Lehane grade noted by laryngoscopy. Appropriate sized ILMA inserted as per standard technique and proper placement confirmed. Appropriate sized PVC tube was passed through the ILMA and its position in trachea confirmed. If intubation failed, two more attempts were allowed by rotating the tube 1800 before passing through ILMA. Number of attempts required for ILMA placement, intubation, success rate of intubation were noted. Complications such as desaturation, laryngospasm, sore throat, hoarseness were recorded if any. Results: Proper ILMA placement was successful in all patients. Blind intubation with PVC endotracheal tubes through ILMA was successful in 194 (97%) patients. There was no correlation between mouth opening, Mallampatti grade, thyromental distance, Cormack Lehane grade, neck circumference, ULBT class and success rates of ILMA insertion and intubation. Mean thyromental distance was 7.5 ± 0.8 cm in those intubated successfully and 5.5 ± 0.3 cm in failed intubations (p <0.001, Mann Whitney U test). Twenty two patients had sore throat and 29 patients had hoarseness of voice. Conclusion: Thyromental distance less than 5 cm is associated with increased number of attempts for intubation and failed intubation and no other airway assessment parameters influence the success rate of ILMA insertion and intubation.