title: Magnetic resonance imaging study of the in vivo position of the extraglottic airway devices i-gel™ and LMA-Supreme™ in anaesthetized human volunteers.
abstract: BACKGROUND
  Exact information on the anatomical in situ position of extraglottic airway (EGA) devices is lacking. We used magnetic resonance imaging (MRI) to visualize the positions of the i-gel™ and the LMA-Supreme™ (LMA-S) relative to skeletal and soft-tissue structures.
  
  
  METHODS
  Twelve volunteers participated in this randomized, prospective, cross-over study. Native MRI scans were performed before induction of anaesthesia. Anaesthesia was induced, and the two EGAs were inserted in a randomized sequence. Their positions were assessed functionally, optically by fibrescope, and with MRI scans of the head and neck.
  
  
  RESULTS
  The LMA-S protruded deeper into the upper oesophageal sphincter than the i-gel™ (P<0.001). Both devices reduced the area of the glottic aperture (P<0.001), and the LMA-S had the largest effect (P=0.049). The i-gel™ significantly compressed the tongue (P<0.001). Both devices displaced the hyoid bone ventrally (P<0.001); the i-gel™ to a greater degree (P=0.029). The fibreoptically determined position of the bowl of the devices was identical.
  
  
  CONCLUSIONS
  The LMA-S and i-gel™ differ significantly with regard to in situ position and spatial relationship with adjacent structures assessed by MRI, despite similar clinical and fibreoptical findings. This could be relevant with regard to risk of aspiration, glottic narrowing, and airway resistance and soft-tissue morbidity.
authors.affiliation: Department of Anaesthesiology, Emergency and Intensive Care Medicine, Göttingen University Medical Centre, Robert-Koch-Strasse 40, 37075 Göttingen, Germany. s.russo@medizin.uni-goettingen.de
authors.forename: S G
authors.initials: SG
authors.lastname: Russo
authors.forename: S
authors.initials: S
authors.lastname: Cremer
authors.forename: C
authors.initials: C
authors.lastname: Eich
authors.forename: M
authors.initials: M
authors.lastname: Jipp
authors.forename: J
authors.initials: J
authors.lastname: Cohnen
authors.forename: M
authors.initials: M
authors.lastname: Strack
authors.forename: M
authors.initials: M
authors.lastname: Quintel
authors.forename: A
authors.initials: A
authors.lastname: Mohr
mesh_terms: D000328:Adult; D000768:Anesthesia, General; D018592:Cross-Over Studies; D004209:Disposable Equipment; D004867:Equipment Design; D005260:Female; D005336:Fiber Optic Technology; D005931:Glottis / Q000033:anatomy & histology; D006801:Humans; D007442:Intubation, Intratracheal / Q000295:instrumentation* / Q000379:methods; D017214:Laryngeal Masks; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D015588:Observer Variation; D011446:Prospective Studies; D014132:Trachea / Q000033:anatomy & histology; D055815:Young Adult