SAFETY FEATURES OF ANAESTHESIA MACHINE

1. SAFETY FEATURES IN
ANAESTHESIA MACHINE
DR. MAHESWARI JAIKUMAR
maheswarijaikumar2103@gmail.com

2. SAFETY FEATURES IN
ANAESTHESIA MACHINE
• The anaesthesia machine is
designed with safety devices as
follows

3. SAFETY DEVICES IN
ANAESTHESIA MACHINE
Pneumatic components
High Pressure Systems
Low Pressure Systems
Pin Index System
Colour Coding
Pressure Regulator
Intermediate Pressure System

4. • Pipe Line Pressure Gauze
• O2 Failure Safety Device
• O2 Safety Valve
• Gas Selector Switch
• Stage Pressure Regulator
• O2 Flush
• Flow Control Knob
• Hypoxia Prevention Device

5. • Mechanical Linkage
• Electronic linkage
• Unidirectional Check Valve
• Pressure Relief Device
• Common Gas Outlets
• Different Tubes for different Gas

6. FRONT VIEW OF ANAESTHESIA
MACHINE

7. BACK VIEW OF ANAESTHESIA
MACHINE

8. PNEUMATIC COMPONENTS
• The anaesthesia machine has
pneumatic components that
ensures safety foe the patients as
follows:
• 1) High Pressure System
• 2) Intermediate Pressure System
• 3) Low Pressure System.

9. HIGH PRESSURE SYSTEM
• A) Hanger Yoke Assembly :- Gate Nipple
Washer Retaining screw Yoke plug

10. PIN INDEX SYSTEM
• Prevents wrong cylinder attachment. -
Presence & Integrity of pins should be
checked.
• Filter :- Prevents dust & foreign
particles from entering.
• Unidirectional valve :- - Prevents
backflow into the cylinder when
cylinder pressure falls below the
pressure inside the machine.

11. COLOUR CODING
• Colour coding of cylinders used for
same gas in machine. caps, hoses,
flow control knobs, Pressure gauges
ensures patient safety

12. PRESSURE REGULATOR
• There are separate regulator for
each gas, and cylinder output
reduced to 45 psig Pipeline output
reduced to 50-55 psig

13. INTERMEDIATE PRESSURE SYSTEM
• The intermediate pressure system
comprises of pipeline inlet
connections, Fitted with threaded
non-interchangeable DISS and
colour coded for gases.

14. PIPE LINE PRESSURE GAUGE
• Is Colour coded for each gas.
• Is Present on the pipeline side of the
unidirectional valve ( If present on the
machine side – will show cylinder
pressures)
• Thus wont read 0 if pipeline supply
fails.
• The piping inside the machine is able to
withstand 4 times the intended service
pressure.

15. OXYGEN FAILURE SAFETY DEVICE
• With respect to Oxygen Fail Safe Valve
& N2O Shut off Valve ASTM Stds require
that, whenever O2 supply pressure falls
below manufacturer specified min
pressure, the delivered O2 conc at the
CGO should not fall below 19%. • If O2
pressure falls – N2O pressure falls
proportionately. • If O2 supply fails –
N2O is shut off.

16. CHECKING O2 SAFE VALVE
• Switch on the flows of N2O & O2 in flow
meters.
• Disconnect O2 pipeline/ Close the cylinder
valve.
• N2O flow indicators falls to 0 even before the
O2 indicator falls
• O2 Failure Safety Alarm :- Alarm will set of
when O2 pressures fall below specified
minimum. (Usually 30 psig) Not possible to
silence unless the pressure is restored

17. GAS SELECTOR SWITCH
• Present in some machines prevents
Air & N2O from being used together.

18. STAGE PRESSURE REGULATOR
• Reduces pressures further to : O2 –
14 psi N2O – 26 psi
• Provides a stable pressure to flow
meters i.c.o. pipeline pressure
fluctuation.

19. OXYGEN FLUSH
• Delivers high flows (35-75 L/min) at
intermediate pressures.
•Can be activated even if the master switch is
off.
• Inappropriate & long activation –
Barotrauma & Awareness to dilution is
designed as “Single purpose, self closing
device & recessed”
• Usually recessed/ placed in a collar – to
prevent accidental activation

20. FLOW CONTROL KNOB
• There is only 1 flow control for each
gas.
• Is colour coded for each gas.
• Appears in different size,
consistency & position. eg :- O2 –
larger & fluted & on the right side/
downstream.

21. LOW PRESSURE SYSTEM
• Flow meter assembly : Stops @ full ON &
OFF pos. Stop at full on pos – at top ↓ a)
Prevents escape of indicator from tube to
common manifold.
• Prevents blockade of common manifold by
the stop.
• Prevents indicator from ascending to the top
where it cant be seen clearly. Stop collar to
flow meter knob – prevents damage to seat
by pin when tightened.

22. DIFFERENT TUBES FOR
DIFFERENT GAS
• Tubes vary in diameter & calibration.
• Tubes made leak proof by “O-rings”
(Neoprene washers) at both the ends.
• Tubes are coated with anti-static coating
on both surfaces ↓ prevents indicator
from sticking.
• Made of glass – transparent material ↓
indicator clearly visible throughout the
tube.

23. HYPOXIA PREVENTION DEVICE
• Mandatory Min O2 Flow (MMOF) A
MMOF – 50-250 ml/min – must as soon
as the master switch is turned on and O2
flow – can’t be reduced below that.
Some machines alarms when O2 flow
falls below MMOF.
• Min O2 Ratio : ASTM Stds require that;
A Min O2 ratio/ Min O2 conc of 21% in
the FGF at CGO. 2 types of linkages to
achieve this.

24. MECHANICAL LINKAGE
• Mechanical Linking of O2 & N2O. O2
– 14 tooth sprocket, & N2O – 29
tooth sprocket Connected by metal
chain.
• Both knobs turn together – to
maintain min 25% O2 conc.

25. ELECTRONIC LINKAGE
• An electronic proportionating valve ↓
maintains min 25% O2 conc in FGF.
• A computer continuously calculates the
N2O flow for the given O2 flow ↓ If
higher N2O flow & O2 conc <25% ↓
Electronic proportionating valve
automatically reduces N2O flow
• Alarms is set off when O2:N2O falls
below a preset value.

26. UNIDIRECTIONAL CHECK VALVE
• Location :- Downstream to vaporisers
Upstream to the point where O2 flush meets
FGF.
• Positive pressures generated within the ckt.s
(eg – during controlled ventilation, when O2
flush is used) ↓ if transferred back to the
machine ↓ dilution of volatile agents &
interfere with the outflow through flow
meters & vaporisers.

27. • Prevents +ve pressures within the
ckt.s to be transferred to the
machine.
• Disadvantage :- Leaks upstream to
the valve cant be detected.

28. PRESSURE RELIEF DEVICES
• Location :- Downstream to the
unidirectional valve Upstream to the
point where O2 flush joins FGF.
• To protect machine from high pressures.
Opens & vents gases to atmosphere
when preset pressure is exceeded.
• Disadvantage :- Limits ability of the
machine to provide adequate pressures
↓ Jet ventilation cant be provided

29. COMMON GAS OUTLETS
• ASTM stds require that;- It should be
difficult to accidently disconnect the
delivery hose from the CGO. ↓ Thus
fitted with std 15mm female slip joint
fitting with 22mm coaxial male
connector.
• Some machines have 2 CGOs ↓ ASTM
stds require that;- Only 1 CGO must be
functional at a time.

30. THANK YOU