Physical properties of nitrous oxide-oxygen sedation equipment used in dentistry

The breathing circuits in eight types of commercially available nitrous oxide-oxygen sedation equipment, with and without gas scavenging devices in operation, were tested with respect to resistance to breathing, carbon dioxide retention and the dilution of the administered gas by fresh air drawn into the circuit. The equipment was designed for use in dentistry. Several of the systems had one or more of the following drawbacks: high resistance to high gas flow, carbon dioxide retention or dilution of the gas mixture by air, the functions being affected by the scavenging equipment. Only one modified circuit showed a high standard of performance in these respects.