Confirmation of laryngeal mask airway placement by ultrasound examination: a pilot study

Abstract

Study ObjectiveWe sought to validate ultrasound against other established methods of confirming laryngeal mask airway (LMA) placement. DesignAn observational study. SettingA university teaching hospital, operating department. PatientsFifty-eight patients undergoing general anesthesia using an LMA Supreme supraglottic airway device. InterventionsThe position of the LMA was assessed by ultrasound in 3 planes: the pharynx, the larynx, and along the cranial-caudal axis in the midline. The leakage test at 20 cm H2O and fiberoptic examination were also undertaken independently, with the latter being used to detect suboptimal placement (in which case, the LMA was reinserted). MeasurementsWe scored the position of the LMA based on the location of the cuff and whether it had inflated correctly in each of the 3 planes. This score was converted to correspond with the leakage test grading system. We tested the strength of the correlation between the scores and the sensitivity and specificity for predicting reinsertion. Main ResultsSeven patients (12.1%) required LMA reinsertion, and ventilation was inadequate in a further 6 (10.3%). Three patients (5.2%) developed laryngospasm and inspiratory stridor after insertion resulting in inadequate ventilation, but none needed reinsertion as optimal placement was confirmed by fiberscope. Spearman coefficient of rank correlation between the leakage test and ultrasound examination was 0.713 (P< .0001). The κ test and Bland-Altman analysis showed good agreement between the 2 scoring systems (weighted κ = 0.605, standard error = 0.086). An ultrasound examination score equating to grade 3 in the leakage test predicted the need for reinsertion with a sensitivity and specificity of 85.7% and 94.1%, respectively. ConclusionsUltrasound examination is a fast, noninvasive and reliable means of detecting LMA misplacement that agrees closely with the leakage test. Ultrasound is as effective as a fiberoptic examination to confirm LMA placement and indicate the need for reinsertion, but does not require ventilation to be interrupted.