title: Time-related cuff pressures of the laryngeal tube with and without the use of nitrous oxide.
abstract: The Laryngeal tube (VBM Medizintechnik, Sulz, Germany), a new supraglottic airway, consists of an airway tube, two cuffs, and two distal apertures between the two cuffs. One concern with the use of this device is ischemic change to the oropharyngeal mucosa. We studied the time-course change of the intracuff pressure (which reflects the pharyngeal pressure) of the laryngeal tube during anesthesia with and without nitrous oxide. After insertion of a laryngeal tube, 24 patients were randomly allocated to 1 of 2 groups. In one group (group N or nitrous oxide group), 66% nitrous oxide was used, whereas in the other group nitrous oxide was not used (group A or air group). In both groups, sevoflurane was used to maintain anesthesia. Time-course changes of the intracuff pressure and postoperative airway complications were recorded. In group N, the intracuff pressure significantly increased over time (P < 0.001; the maximal pressure: 120 cm H(2)O), whereas in group A the intracuff pressure remained stable. The intracuff pressure was significantly higher in group N than in group A (P < 0.0001; 95% confidence intervals for difference: 6-20 cm H(2)O at 30 min). Postoperatively, two patients in group A and one patient in group N complained of mild sore throat.
  
  
  CONCLUSIONS
  Nitrous oxide may increase pharyngeal pressure by the cuffs of the laryngeal tube, and thus it is advisable to monitor and adjust the intracuff pressure of the laryngeal tube during anesthesia to minimize possible ischemic changes to the oropharynx.
authors.affiliation: Department of Anesthesiology, Kansai Medical University, Osaka, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Asai
authors.forename: Koh
authors.initials: K
authors.lastname: Shingu
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D006801:Humans; D017214:Laryngeal Masks; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000295:instrumentation* / Q000379:methods*; D009609:Nitrous Oxide / Q000494:pharmacology*; D011312:Pressure; D018709:Statistics, Nonparametric; D013997:Time Factors
chemical_list: D009609:Nitrous Oxide