Evaluation of the LMA Position Using Ultrasound in Pediatric Patients

Introduction: Although the LMA insertion is not difficult and majority of the cases with LMA fare well in ventilation, the FOB assessment demonstrates a high incidence of LMA malpositioning. The LMA must be seated at the laryngeal inlet with the occlusion of esophageal inlet by the inflated tip. When we meet the signs of LMA malposition, we then reinsert the LMA. The laryngoscopic grading of Rowbottom et al. is commonly used for LMA position, but the rotated degree of LMA was not considered in that grading. We hypothesized that the LMA can affect the position of the arytenoids/thyroid cartilages and it may be detected on ultrasound. This study was designed to assess the predictability of the rotated LMA according to the position change of arytenoids/thyroid cartilages using ultrasound.

Methods: Children, aged 1 ms - 6 years, undergoing infraumbilical surgery were enrolled to this study. Ultrasound was performed on supraglottic and vocal cords area before and after LMA insertion. Transverse images were obtained on end-expiratory phase. LMA-position was evaluated with Bonfils fiberscopy. Position grading was made as usual. If grade >3 was showed, LMA was repositioned while fiberscopic watching. If the face of LMA was rotated to one-side, the LMA was rotated to the opposite side a little. The ultrasound findings of pre- and post-LMA were compared. On fiberscopic images, conventional LMA grade and the degree of rotation were measured.