Ultrasound-guided hyomental distance versus weight-based method for ProSeal LMA™ size selection: A randomised controlled study.

BACKGROUND AND AIMS: Conventional weight-based laryngeal mask airway (LMA) size selection does not consistently correlate with individual upper airway anatomy, leading to suboptimal device fit. Ultrasound-guided measurement of hyomental distance (HMD), an indicator of submandibular space, has emerged as a promising anatomy-based alternative. This study aimed to compare the efficacy and safety of ultrasound-guided HMD-based sizing with conventional weight-based sizing of the ProSeal LMA™ (Teleflex Inc., Wayne, PA, USA) (PLMA) in adult patients undergoing elective surgery.

METHODS

This prospective, double-blinded randomised controlled trial included 116 American Society of Anesthesiologists (ASA) physical status I-II adults aged 18-60 years scheduled for elective surgery under general anaesthesia. Patients were randomised into two groups: Group A underwent PLMA size selection based on body weight, while Group B underwent ultrasound-guided HMD-based size selection. The primary outcome was first-attempt insertion success. Secondary outcomes included insertion time, number of attempts, need for reinsertion, and postoperative oral injury.

RESULTS

Demographic characteristics were comparable between groups. First-attempt insertion success was similar in both groups (93.1% in weight-based group vs. 96.6% in HMD group; P = 0.67). The mean insertion time was comparable (18.1 ± 4.8 s vs. 18.5 ± 4.6 s; P = 0.60). The HMD group predominantly received smaller PLMA sizes (P < 0.001) without increased reinsertion rates or complications. Postoperative oral injury was rare and comparable between groups.

CONCLUSION

Ultrasound-guided HMD-based PLMA sizing provides an individualised, anatomy-based alternative to weight-based selection, achieving comparable insertion success, efficiency, and safety while favouring anatomically appropriate device sizing.