Assessment of Neck Characteristics for Laryngeal Mask Airway Size Selection in Patients Who Underwent an Elective Ocular Surgery; A Cross-Sectional Study

Objective: To investigate the neck features for laryngeal mask airway (LMA) size selection. Methods: This cross-sectional study was conducted on 160 patients referred for elective surgeries to Feiz Hospital affiliated with Isfahan University of Medical Sciences, Isfahan, Iran (April 2016 to September 2018). Patients underwent ventilation using LMA whose size was determined through a weighted-based approach. All of the patients’ neck characteristics including circumference, thyromental distance, and opening mouth were measured. Ventilation factors were recorded including numbers of attempts for successful LMA insertion, quality of ventilation, and sealing. Results: Neck circumference and thyromental distance were significantly different with the size of LMA (p<0.0001 and p=0.005, respectively), but not mouth opening (p=0.21). Neck circumference, thyromental distance, and mouth opening were not significantly different with the times of insertion attempts (p>0.05 for all comparisons). However, the thyromental distance was significantly different with the quality ventilation status (p<0.0001). The total assessment of insertion attempts, ventilation efficacy and sealing was significantly different with the neck circumference (p<0.001), but thyromental distance did not show a significant difference (p>0.05). Conclusion: Findings demonstrated that neck circumference might be considered as an appropriate indicator for the selection of LMA size but neither the thyromental distance nor mouth opening. Further studies with a larger sample size are strongly recommended.