Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content ++ Oxygen deliveryCO2 removalAnesthetic agent administration ++ See following table. ++Table Graphic Jump Location|Download (.pdf)|PrintCircuit Classifications (Open vs. Closed or Rebreathing vs. Non-Rebreathing)OpenInsufflationBlowing of oxygen or anesthetic gas over the patient’s face via mask or head drapeNo rebreathingOpen dropNo longer used. Modern version is the drawover apparatus; useful when compressed gases are not availableSemi-openMapleson breathing systems (A, B, C, D, E, F)Portable, inexpensive but require high fresh gas flow (FGF)Consist of a varied arrangement of FGF, breathing bag, reservoir tubing, expiratory/overflow valveNo unidirectional valves, so rebreathing can occur if FGFs are not appropriateMapleson A: most economic for spontaneous breathingMapleson D/Bain: most economic for controlled ventilationSemiclosedCircle systemMost common arrangement used in modern anesthesiaBecause air is rebreathed, CO2 must be removedConsidered “semi-open” because there is only partial rebreathing since some gas is lost from the APL/scavenger systemHelps to maintain heat, humidity, decrease the required amount of FGF, decrease pollution of atmosphereRebreathingClosedCircle systemAs above; however, there is total rebreathing of exhaled air (i.e., FGF is approximately equal to patient’s basal O2 requirement with anesthetics)Makes quick changes in gas/anesthetics difficult ++ See following table. ++Table Graphic Jump Location|Download (.pdf)|PrintMapleson System ClassificationRequired fresh gas flowsMapleson classOther namesConfiguration1SpontaneousControlledCommentsAMagill attachmentEqual to minute ventilation (≈80 mL/kg/min)Very high and difficult to predictMost efficient for spontaneous ventilationPoor choice during controlled ventilationB2 × minute ventilation2–2.5 × minute ventilationNot used in modern practiceCWater’s to-and-fro2 × minute ventilation2–2.5 × minute ventilationNot used in modern practiceDBain2–3 × minute ventilation1–2 × minute ventilationBain coaxial modification: fresh gas tube inside breathing tube (to warm fresh gas). Most efficient for controlled ventilationEAyre’s T-piece2–3 × minute ventilation3 × minute ventilation (I:E = 1:2)Exhalation tubing should provide a larger volume than tidal volume to prevent rebreathing. Scavenging is difficult. Decreased resistance in circuit conducive to weaningFJackson Rees2–3 × minute ventilation2 × minute ventilationA Mapleson E with a breathing bag connected to the end of the breathing tube to allow controlled ventilation and scavenging. Commonly used for pediatric patients and transportation1FGI, fresh gas inlet; APL, adjustable pressure limiting (valve). ++Table Graphic Jump Location|Download (.pdf)|PrintCircle System: Essential ComponentsCharacteristicsPotential hazardGas supplyCarrier gases (O2, N2O, air) supplied to anesthesia machine via central supply of hospital or portable E cylindersVariable, high-pressure system from cylinders. Regulators decrease pressure to ˜45 psi. Some machines employ a second regulator that further reduces the pressure to ˜12–16 psiIncorrect identification can be fatalColor system for cylinders and hoses (i.e., O2, ... Your Access profile is currently affiliated with '[InstitutionA]' and is in the process of switching affiliations to '[InstitutionB]'. Please click ‘Continue’ to continue the affiliation switch, otherwise click ‘Cancel’ to cancel signing in. Get Free Access Through Your Institution Learn how to see if your library subscribes to McGraw Hill Medical products. Subscribe: Institutional or Individual Sign In Username Error: Please enter User Name Password Error: Please enter Password Forgot Username? Forgot Password? Sign in via OpenAthens Sign in via Shibboleth