title: The closed co-axial analgesia system.
abstract: A twin-tube system for nitrous oxide analgesia in dental surgeries is described. The system is a non-polluting modification of the Mapleson A system, employing the principle of co-axial tubing introduced by Bain & Spoerel (1972). Active, continuous and calibrated gas removal takes place via the co-axial tubing by means of an ejector flowmeter. Investigation of the dynamic pressure excursions occurring at the nose-piece are fully compatible with normal breathing. Gas contamination of the dental environment can be reduced by at least 90%. The system described is safe and easy to handle. It is made of light-weight material and is adaptable to the equipment available. No rebreathing takes place when using a fresh gas inflow of 150 ml/kg body weight/min.
mesh_terms: D000397:Air Pollution / Q000517:prevention & control; D000399:Air Pressure; D000698:Analgesia / Q000295:instrumentation*; D000766:Anesthesia, Dental / Q000295:instrumentation*; D000769:Anesthesia, Inhalation / Q000295:instrumentation*; D006801:Humans; D012119:Respiration