title: The effect of changing the sequence of cuff inflation and device fixation with the LMA-Supreme® on device position, ventilatory complications, and airway morbidity: a clinical and fiberscopic study.
abstract: BACKGROUND
  The conventional sequence when using supraglottic airway devices is insertion, cuff inflation and fixation. Our hypothesis was that a tighter fit of the cuff and tip could be achieved with a consequently lower incidence of air leak, better separation of gastrointestinal and respiratory tracts and less airway morbidity if the device were first affixed and the cuff then inflated.
  
  
  METHODS
  Our clinical review board approved the study (public registry number DRKS00003174). An LMA Supreme® was inserted into 184 patients undergoing lower limb arthroscopy in propofol-remifentanil anaesthesia who were randomly assigned to either the control (inflation then fixation; n = 92) or study group (fixation then inflation; n = 92). The cuff was inflated to 60 cmH2O. The patients' lungs were ventilated in pressure-controlled mode with 5 cmH2O PEEP, Pmax to give 6 ml kg-1 tidal volume, and respiratory rate adjusted to end-tidal CO2 of 4.8 and 5.6 kPa. Correct cuff and tip position were determined by leak detection, capnometry trace, oropharyngeal leak pressure, suprasternal notch test, and lube-tube test. Bowl and cuff position and the presence of glottic narrowing were assessed by fiberscopic examination. Postoperative dysphagia, hoarseness and sore throat were assessed with a questionnaire. Ventilatory impairment was defined as a tidal volume < 6 ml kg-1 with Pmax at oropharyngeal leak pressure, glottic narrowing was defined as an angle between the vocal cords under 16 degrees.
  
  
  RESULTS
  The incidence of incorrect device position (18% vs. 21%), failed ventilation (10% vs. 9%), leak pressure (24.8 vs. 25.2 cmH2O, p = 0.63), failed lube-tube test (16.3% vs. 17.6%) and glottic narrowing (19.3% vs. 14.1%, p = 0.35) was similar in both groups (control vs. study, resp.). When glottic narrowing occurred, it was more frequently associated with ventilatory impairment in the control group (77% vs. 39%; p = 0.04). Airway morbidity was more common in the control group (33% vs. 19%; p < 0.05).
  
  
  CONCLUSIONS
  Altering the sequence of cuff inflation and device fixation does not affect device position, oropharyngeal leak pressures or separation of gastrointestinal and respiratory tracts. It reduces the incidence of glottic narrowing with impaired ventilation and also perioperative airway morbidity.
authors.affiliation: Department of Anaesthesiology, Emergency and Intensive Care Medicine, University of Göttingen Medical School, Robert-Koch Str, 40, 37075 Göttingen, Germany. Ingo.Bergmann@med.uni-goettingen.de.
authors.forename: Ingo
authors.initials: I
authors.lastname: Bergmann
authors.forename: Thomas Allen
authors.initials: TA
authors.lastname: Crozier
authors.forename: Markus
authors.initials: M
authors.lastname: Roessler
authors.forename: Hanna
authors.initials: H
authors.lastname: Schotola
authors.forename: Ashham
authors.initials: A
authors.lastname: Mansur
authors.forename: Benedikt
authors.initials: B
authors.lastname: Büttner
authors.forename: José Maria
authors.initials: JM
authors.lastname: Hinz
authors.forename: Martin
authors.initials: M
authors.lastname: Bauer
mesh_terms: D000328:Adult; D000768:Anesthesia, General / Q000295:instrumentation / Q000379:methods*; D004867:Equipment Design / Q000295:instrumentation / Q000592:standards; D005260:Female; D005931:Glottis / Q000033:anatomy & histology / Q000502:physiology; D006801:Humans; D017214:Laryngeal Masks / Q000592:standards; D020704:Laryngoscopes / Q000592:standards; D007828:Laryngoscopy / Q000295:instrumentation / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012123:Pulmonary Ventilation / Q000502:physiology*