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

 

Principles:

Goals

      No hypoxia

      No barotrauma

      No explosion

Supply design

      Multiple oxygen sources

      Multiple pressure regulators

      Multiple alarms

 

Oxygen sources:

Cylinder

      Label

      Colour code: white body, white shoulders

      Pin index safety system (2&5)

      Outlet melts and occludes if heated

      Bodok seal non-combustible, gas-tight

Pipeline

      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

Pressure

      Systems:

o   High (16atm) cylinder and attachments

o   Intermediate (4atm) gas supply lines

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

      Valves:

o   Check valves prevent backflow

o   Pressure regulators smooth pressure drop between sections

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

Power

      Wall source (connected to uninterruptable supply)

      Back-up battery

      On-off button in-set

Alarms

      Power supply

      Pressure gauges

      FiO2 and etO2 paramagnetic analyser

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

 

 

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