Nitrous oxide sedation in dentistry. A comparison between Rotameter settings, pharyngeal concentrations and blood levels of nitrous oxide.

Nitrous oxide concentrations (V/V) at the delivery Rotameters block, nasal mask, pharynx and venous blood, were compared. There was a dilution of approximately 50% of the delivered nitrous oxide at the nasal mask which was further reduced in the pharynx. Venous blood concentrations 10 minutes after inhalation of nitrous oxide were low but as would be calculated from pharyngeal concentrations. After 5 minutes of oxygenation venous blood nitrous oxide concentrations were still relatively high. A total of 92% of subjects experienced a satisfactory effect with 30% nitrous oxide or less in the pharynx.