End-expired nitrous oxide concentrations compared to flowmeter settings during operative dental treatment in children

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.

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.

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.

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.