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

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

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