Hyomental distance measured by ultrasound for size selection of laryngeal mask airway in female patients: a randomized controlled study

Abstract BackgroundOptimal size selection of classic laryngeal mask airway (LMA) remains a major challenge for anaesthesiologists. Because the body weight, current method to select LMA size, might not inconsistent with dimension of hypopharynx where LMA is positioned. Hyomental distance by ultrasound as an common parameter in upper airway may be considered a predictor of LMA size choice, that we conducted a randomized, controlled study to compare the efficacy of size selection between commonly recommended weight-based method and hyomental distance-based method.MethodsSeventy female patients undergoing breast cancer surgery were enrolled in our study and randomly assigned into either the hyomental distance group or weight group. The primary outcome was the correct rate of selection LMA without need for size adjustment or use of other devices. Secondary outcomes included injury rate, oropharyngeal leak pressure (OLP), and insertion attempts.ResultsTwo participants were excluded from weight group due to tracheal intubation. The correct rate of LMA size-selected were significant difference of 77.14% and 51.51% in hyomental distance group and weight group, respectively(P=0.027). Five (14.29%) and 7 (21.21%) patients were injured in hyomental-distance group and weight group, respectively. Values of OLP in two groups were 22 (19-24) cmH2O and 22 (19.5-24) cmH2O, respectively. The insertion attempts were the same in both groups and no statistical differences were observed regarding these three outcomes. ConclusionThe hyomental distance-based method possessed a higher success rate for LMA-classic size selection than did the weight-based method, with the same excellent OLP value, low possibility of injury, and a low number of insertion attempts as weight-based method. Trial registrationOur study was registered with the Chinese Clinical Trial Registry (ChiCTR1900021123), registered 29 January 2019.