2021B13. For each of the following, describe the features that ensure the safe delivery of oxygen during anaesthesia. a) cylinders b) pipeline supply c) anaesthesia machines




      No hypoxia

      No barotrauma

      No explosion

Supply design

      Multiple oxygen sources

      Multiple pressure regulators

      Multiple alarms


Oxygen sources:



      Colour code: white body, white shoulders

      Pin index safety system (2&5)

      Outlet melts and occludes if heated

      Bodok seal non-combustible, gas-tight


      Label: socket and hose

      Colour code: white hose, white screw collar

      Diameter index safety system

      Anti-kink tube


Anaesthesia machine:

Fresh gas supply

      Oxygen is the last to enter the stream

      Oxygen control knob (if present) is colour coded, larger, protuberant

      Chain-link between O2 and N2O flowmeters (physical or electronic)

      Oxygen failure (usually <2atm) -> open fail-safe valve, other gas off

      Usually no protection against hypoxia from low FiO2 with low FGF rate

Alternative supply

N.B. no electricity required:

      Oxygen safety flow (0-10L/min)

o  Into fresh gas supply

o  Master control switch must be on

      Oxygen flush (40-60L/min, 4 atm)

o  Bypasses circuit

o  Button in-set to prevent accidental barotrauma

      Auxiliary source (0-10L/min)

o  Separate to circuit

      Bag-mask resuscitator

o  Separate to machine



o   High (16atm) cylinder and attachments

o   Intermediate (4atm) gas supply lines

o   Low (<70cmH2O) fresh gas, vapourisers, circuit
(i.e. patient interface)


o   Check valves prevent backflow

o   Pressure regulators smooth pressure drop between sections

o   Pressure relief valves e.g. APL valve 0-70cmH2O


      Wall source (connected to uninterruptable supply)

      Back-up battery

      On-off button in-set


      Power supply

      Pressure gauges

      FiO2 and etO2 paramagnetic analyser

      Oxygen failure activated if supply <2atm, cannot be silenced



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