title: End-expired nitrous oxide concentrations compared to flowmeter settings during operative dental treatment in children.
abstract: OBJECTIVE
  The purpose of this study was to analyze inspired and end-expired alveolar nitrous oxide (N(2)O) concentrations during operative dental treatment in 6- to 9- year-old children and compare them to the concentrations dispensed by the dental N(2)O delivery system's flowmeter.
  
  
  METHODS
  Twenty-three healthy 6- to 9-year-olds who received restorative dental care underwent placement of a sampling probe in the posterior nasopharynx. Via nasal mask, 100% oxygen was administered at a rate of 3L/minute for 2 minutes. N(2)O was then introduced at a flowmeter reading of 50% for 5 minutes and thereafter reduced to 30% for the duration of treatment, followed by 100% oxygen for 5 minutes postoperatively. Respiratory rate, inspired and end-expired nitrous oxide and oxygen concentrations, and pressure of end-tidal carbon dioxide values were measured and recorded from the nasopharyngeal probe with an anesthesia gas monitor.
  
  
  RESULTS
  End-expired alveolar N(2)O concentrations were, on average, 63% below flowmeter settings. After rapid induction with 50% N(2)O, an end-expired N(2)O saturation maximum of 11% was attained, on average, after 90 seconds. The time to flush out remaining N(2)O after delivery of 100% oxygen varied between 30 and 195 seconds.
  
  
  CONCLUSIONS
  End-expired alveolar nitrous oxide and oxygen concentrations and pressure of end-tidal carbon dioxide values were successfully recorded during operative dental treatment of 6- to 9-year-old awake and non-intubated children in the traditional dental setting.
authors.affiliation: Department of Pediatric Dentistry, The Children's Hospital and School of Dental Medicine, University of Colorado Denver, Aurora, Colo, USA. klein.ulrich@tchden.org
authors.forename: Ulrich
authors.initials: U
authors.lastname: Klein
authors.forename: T Jay
authors.initials: TJ
authors.lastname: Robinson
authors.forename: Amanda
authors.initials: A
authors.lastname: Allshouse
mesh_terms: D000766:Anesthesia, Dental / Q000379:methods*; D018685:Anesthetics, Inhalation / Q000008:administration & dosage / Q000032:analysis*; D001944:Breath Tests; D002245:Carbon Dioxide / Q000032:analysis; D002648:Child; D016292:Procedural Sedation / Q000379:methods*; D003793:Dental Restoration, Permanent; D045853:Exhalation; D045268:Flowmeters; D006801:Humans; D001239:Inhalation; D008397:Masks; D009305:Nasopharynx; D009609:Nitrous Oxide / Q000008:administration & dosage / Q000032:analysis*; D010100:Oxygen / Q000032:analysis; D010313:Partial Pressure; D056152:Respiratory Rate; D013990:Tidal Volume; D013997:Time Factors
chemical_list: D018685:Anesthetics, Inhalation; D002245:Carbon Dioxide; D009609:Nitrous Oxide; D010100:Oxygen