1. SAFETY FEATURES IN
ANAESTHETIC MACHINES
-Dr.Prem kumar,
Department of anesthesiology,
Madras medical college

2. Why safety features?
 To safeguard human life from unknown
human errors.
 Safety devices are to prevent delivery of
hypoxic mixture
 Regulation to prevent excessive pressure
which is traumatic to patient.

3. Statistics
Misuse: 70% direct action primary anesthesia provider
30% contributory actions of ancillary personnel

4. Classification
 ELECTRICAL COMPONENTS
 PNEUMATIC COMPONENTS.

5. ELECTRICAL
COMPONENTS
 Master switch
 Power failure indicator
 Reserve power
 Automated check out

6. PNEUMATIC SYSTEM
 High pressure system
 Intermediate system
 Low pressure system
 Alternative oxygen control

7. High pressure system
 GAS CYLINDER –
Color coding
Pin index
Cylinder labels
Safety relief device

9. COLOR CODING
 Oxygen black body,white shoulders[white
for international]
 Nitrous oxide blue
 Air white and black
 Carbon dioxide gray
 Helium brown
 Entonox black with blue/white shoulders

11. PIN INDEX SAFETY SYSTEM
 Air - 1,5
 Oxygen - 2,5
 Nitrous oxide - 3,5
 CO2>7.5% - 1,6
 CO2<7.5% - 2,6
 Cyclopropane - 3,6
 N2O-O2 - 7

14.  The safety relief device is composed of atleast one
of
− Frangible disc [bursts under extreme
pressure]
- Fusible plug [wood’s metal which has a
low melting Point ]
- Safety relief valve [ opens at extreme
pressure ]

15.  WOOD’S METAL
A fusible alloy that contains 50%
bismuth, 25% lead, 12.5% tin, and 12.5%
cadmium, and melts at 158°F (70-72°C);
used for automatic sprinkler plugs.

16.  Cylinder pressure indicator [ bourdon’ s pressure
gauge]
 Pressure regulator - PRIMARY
 Washer [ bodok seal ] – rubber made of neoprene
 Hanger yoke assembly – has pin index safety
system. one way check valve for unidirectional
gas flow

17. Bourdon’s pressure gauge
 Indication of incoming gas supply
 In O2 cylinder – indicates amount of gas
 N2O cylinder – pressure is not indicative of
amount b’cos N2O is stored in liquified
form.
 Curved tube can rupture with high pressure
and the gauge has a vent on its back which
can release the gas in the event of rupture.

19. Pressure regulator

20. Bodok seal

22. Intermediate system
 Pipeline –
- Gas hoses are named and color coded
- Non interchangeable quick
couplers[shrader’s valve-gas specific]
- NIST
- Diameter index safety system[DISS]
- Pipeline pressure indicators

24. NIST

25. - In line filter
- Check valve
- Gas power outlet [auxiliary oxygen
as a source of driving
gas for anesthesia ventilator or jet
ventilation]
 Oxygen pressure failure device
 Oxygen supply failure alarm [ richter alarm]

26. OPFD

27.  Pressure regulators – second stage
 Pressure relief valve
 Oxygen flush - O2+
 Flow control valve – color coding,fluted[O2], size,
distance, placement of knobs,guard

28. PRESSURE REGULATOR

29. Pressure Relief Valve
 Pressure relief valves are installed
downstream of all pressure regulators
 Valves set at no more than 50% above
the pressure regulator setting.
 Function: Fully relieving the pressure at
the set point in case failure of regulator.
 All pressure relief valves have piping
connections to allow release of to outside
facility.

31. Low pressure system
 Flowmeters –
- Bobbin rotates on flow which prevents it
from sticking.
- Bobbin is antistatic to prevent
sticking to the wall of the flowmeter
- Fluorescent coating on the back of
flowmeter panel and on the dot of bobbins
- Float stop
- Arrangement
- Auxiliary oxygen flowmeter

35. An oxygen leak from the flow tube
can produce a hypoxic mixture,
regardless of the arrangement of
the flow tubes

36. Auxiliary oxygen flowmeter

37. Hypoxia prevention safety
devices:
 Proportionating devices –
- link 25 in datex
ohmeda[mechanical,pneumatic
and electronic linkage]
- S-ORC in draeger,
- Mandatory minimum oxygen
flow

39.  Vaporizers - Selectatec mechanism,
interlocking,low filling port, indicator
of agent,increased wick capacity,
Fraser sweatman pin safety system
 Unidirectional [check ] valve
 Back pressure relief valve [opens when the
pressure exceeds 200 cm H2O]
 Common gas outlet

41. Breathing system
 APL valve open when pressure exceeds 60 cm
H2O
 Pressure in reservoir bag shouldn’t exceed 60 cm
H2O.
 Oxygen analyser
 Canister – To prevent co2,carbon monoxide.
Dessicated absorbents without KOH or ba(OH)2
and with lesser amounts of NaOH produce less
heat and no fires.

42.  VENTILATORS – PRESSURE SENSORS TO
DETECT EXCESSIVE AIRWAY PRESSURE
DUE TO VENTILATOR MALFUNCTION
 Alternative oxygen control
 Scavenging system
 Wheels in anesthetic workstation is made of
antistatic rubber.

46. Safety features of newer
machines
 Ø More accurate and/or corrected tidal
volume through compliance and fresh gas
compensation
 Ø Potential return of sampled gas[SGR]
to facilitate low-flow
 Ø Fresh gas decoupling prevent
hyperinflation of the lung

47.  Electronic PEEP
 Electronic selection of ventilation
parameters
 Reduced external connections

48. Thank you