title: The measurement of expiratory oxygen as disconnection alarm.
abstract: The efficacy of an oxygen-monitoring alarm in the expiratory limb of an anesthetic circuit was evaluated as a method of detecting disconnections of the patient from the anesthetic machine. Oxygen concentrations were determined in the expiratory limb of a semiclosed anesthetic circuit with a ventilator and a 2-1 reservoir bag serving as a simple lung model. Adjustments of ventilation during the different measurements were a PEEP of 5 cmH2O, respiratory rates of 10/min and 5/min, and tidal volumes of 1,000 and 500 ml, respectively. The alarm time measured with a stopwatch was the time that elapsed between disconnection and the acoustical alarm. The circuit was always disconnected at the y-piece when the reservoir bag had been fully expanded after an inspiration. With various fresh flow rates and oxygen concentrations ranging from 33% to 52%, disconnection always was evident within 30 s. Measurement of the oxygen concentration with an alarm time of 30 s after disconnection may be an effective backing system for detecting a disconnection.
authors.affiliation: Department of Anesthesia, University of Basel/Kantonsspital, Switzerland.
authors.forename: R
authors.initials: R
authors.lastname: Knaack-Steinegger
authors.forename: D A
authors.initials: DA
authors.lastname: Thomson
mesh_terms: D000776:Anesthesiology / Q000295:instrumentation*; D004868:Equipment Failure; D006801:Humans; D008991:Monitoring, Physiologic; D010100:Oxygen / Q000032:analysis*; D012122:Ventilators, Mechanical
chemical_list: D010100:Oxygen