anesthesia machine

1. Anaesthesia
machine
SPEAKER: DR.Raj kumar A
DNB 3rd year resident
Apex hospital{U.P}

3. Functioning
gas supply
gas inlet
pressure reduction
flowmeter
vapourizer
common gas outlet
breathing circuit
patient

4. FUNCTION OF ANESTHESIA MACHINE
Provide o2
Accurate mixture of anesthetics and
mixture
Enable patient ventilation
Minimise anesthesia related risk to
patient and staff

5. 30-45
PSI 14-26
PSI
55-60
psi
2000
psi

6. PNEUMATIC SYSTEM
HIGH PRESSURE
•
•
•
Cylinders
Hanger Yoke
Cylinder Pressure
Indicator(Gauge)
Pressure Regulators
INTERMEDIAT
E
PRESSURE
Master Switch
Pipeline Inlet
Connections
Pipeline Pressure
Indicators
Piping
Gas Power Outlets
Oxygen Pressure Failure
Devices
Gas Selector Switch
Second stage Pressure
Regulator
Oxygen Flush
Flow Adjustment Control
LOW
PRESSURE
Flowmeter
Unidirectional(Check
Valves
Pressure Relief Device
Low Pressure Piping
Common (Fresh) Gas
Outlet

7. VARIOUS UNITS
• 1 KG/CM2 = 14.223 PSI
• 100KPa =1000mbar=760mm hg=1030 cm h20= 14.7 psi= 1 atm
• 1 psi = 6.895 kpa
• 1 mmhg = 1.36 cm h20 = 1 torr= 1.32mbar
• 1 torr = 133.32 pa
• 1 kPa =7.6 mm hg =0.147 psi
PSI – Pounds per square inch
PSIG – Pounds per square inch gauge
PSIA – Pounds per square inch absolute
PSIA = PSIG + 1 atm
PSIG = PSIA – 1 atm

8. Components
Cylinders- Pressurized container used for storage
and transport.
Boyles machine consist of 2 oxygen ,2 nitrous
oxide
Cylinders are made of chrome molybednum steel 3
mm, aluminium 6 mm .cylinders for m.r.i. room
There are different size of cylinders specified as
A,B,C,D,and others,the size A is smallest, D and E
are in common use
O2 ,N2,AIR in compressed form while N20,CO2
and cyclopropane in liquid form

9. COMPRESSED GAS CYLINDER
Body
Components of a cylinder :
Shoulder Valve
Stem
Port
Fusible material {woods metal}
b/wcylinder and valve

11. International colour code of cylinder
O2-black with white shoulder
N20-blue
C02-grey
cyclopropane –orange
Air-grey with white /black quarters
Entonox-blue with white/blue quarters

12. COMPONENT OF CYLINDER
Valve: bronze/ brass
There are 2 main types of valves
1.diaphragm- valve stem with adjustable
screw,less likely to leak,expensive,
It can be fully opened using only one half to
three quarter turn
2.Packed or flush type –this noninterchangeble
flush type valve(with pin index system) is commonly
used in modern anaesthetic machine
CONICAL DEPRESSION

13. Pressure relief device.
(safety relief device, safety device)
Purpose :to vent the cylinders contents tothe atmosphere if the
pressure of the enclosed gas increases toa dangerouslevel.
TYPES
1) Rupture Disc
2)Fusible Plug
3)COMBINATION
OF 1 & 2
4)Pressure Relief Valve

15. 02- 2,5
N20- 3,5
Cyclo-propane- 3,6
Nitrogen- 1,4
CO2<7. 5%- 2,6
>7.5%- 1,6
Air - 1,5
Entonox- 7

16. Pin index system
It is introduced in1952
Cylinders are locked to machine in yoke
with 2 pins and 2 corrosponding holes
A line is drawn through the centre of
valve outlet at an angle of 30 deg. to
right face of valve.the central point of
position 1 pass through it, arc of radius
9/16 inch,other positions are passes
through intervals of 12 deg
6 mm long 4 mm dia

17. The diameter of valve outlet is 7mm.
Various pin index-
02- 2,5
N20- 3,5
Cyclo-propane- 3,6
Nitrogen- 1,4
CO2<7. 5%- 2,6
>7.5%- 1,6
Air - 1,5
Entonox- 7

18. PRESSURE &
FILLING
Filling ratio- it is the percentage of weight of gas in a
container to weight of water it can hold at 60 f. this is used
to prevent overfilling,N20-0.68,cyclo-0.55
Service pressure-each cylinder contains a gas under
specified pressure,which is known as service pressure.it is
the maximum pressure at 70 f
But able to withstand 1.66 time of the service pressure
Units of pressure( 100kPa = 760mmHg = 14.7psi =1atms)

19. OXYGEN TANK DURATION
Minutesremaining = (PSIG * Tank factor)
Flow rate per min
Tank size Conversion factor
E 0.28
D 0.16
H 3.14
M 1.56

21. Cylinder identification
• Should have a label
a. Name and chemical symbol of gas.
b. Product specification.
c. Hazard warning diamond shaped figuredenoting hazard class
contained gas.
d. Name and address of cylinder manufacturer.
e. Cylinder contents in liters.
f. Tare weight (weight when empty).
g. Maximum cylinder pressure.
h. Cylinder size code.
i. Directions for use.

22. PERIODIC
TESTING
Hydraulic test Is a measure of cylinder’s elasticity
cylinder pressurized to 240 atmospheres.The cylinder
should stretch less than 0.02%.
Tensile test Done in one out of 100 cylinders. The
strips of the cylinder are cut and stretched.
Flattening test The cylinder is kept between two
compression blocks and pressure is applied from both
sides until the distance between blocks remains 6
times the thickness of the wall of cylinder. The walls
should not crack.

23. Impact test
Mean energy to produce the crack
should not be less than 5 and 10 lb/ft for transverse
and longitudinal strips, respectively.
Bend test
A ring of 25 mm width is cut from the cylinder and
divided into strips. Each strip is bent inward until
inner edges are a part, not greater than the diameter
of strip

24. Safety system
Colour coding
Label on cylinder
Valve system
Pin index system

25. Yoke assembly

27. Yoke assembly
It is the portion of machine at which the cylinders are
fitted
The hanger yoke consists of:
(1) The body, which is the
principle framework and supporting structure,
(2) The retaining screw, which tightens the cylinder in the
yoke,
(3) the nipple, through which gas enters the machine,
(4)the index pins, which prevent attaching an incorrect
cylinder,
(5) the Bodok seal,

29. Bourdon’s pressure gauge

30. 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.
Safety system

31. Pressure reducing valve

32. Pressure reducing valve
Converts high variable pressure in
cylinders to constant working
pressure suitable for anaesthesia
machine
The pressure regulators reduce the
pressure of the O2 cylinders from
1900 PSIG to 30-45 PSIG and the
N2O cylinders from 760 PSIG 30-45
PSI

34. 38
Intermediate Pressure System
Receives gasses from the
regulator or the hospital
pipeline at pressures of 55-60
psig
Consists of:
Pipeline inlet connections
Pipeline pressure indicators
Piping
Gas power outlet
Master switch
Oxygen pressure failure devices
Oxygen flush
Additional reducing devices
Flow control valves

35. 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

36. SCHRADE
R

37. DISS

38. NIST

39. 43
Second-Stage Pressure
Regulator
Located just upstream of the flow control
valves
Receives gas from the pipeline inlet or the
pressure regulator and reduces it further to 26
psig for N2O and 14 psig for O2
Purpose is to eliminate fluctuations in pressure
supplied to the flow indicators caused by
fluctuations in pipeline pressure

40. O2
FLUSH
There is a direct tubing connecting the O2 pressure
regulator to the O2 flush. It gives 35-70 L/min of flow
with a pressure of 45-60 PSIG.
Disadvantage: Barotrauma
Awareness

42. Oxygen Supply
Failure Alarm

43. THE FLOW METER ASSEMBLY
The flow meter assembly controls, measures and indicates
the rate of flow of gas passing through it

45. Flow control valves
Flow control valve or needle valves is used at lower end
of flowmeter
It controls the rate of flow of gas through its associated
flow indicator by manual adjustment of a variable
orifice
Gas flow is started, controlled and terminated by
unscrewing and screwing of pin valve

46. Low pressure system
The low pressure system is downstream of the flow
control valves
Pressure in this section is only slightly above
atmospheric
Components found in this section includes flow
indicator vapourizer and common gas outlet

47. 51
Flowmeter

48. 52
Flowmeter Physics
The rate of flow through the
flowmeter tube depends on 3 things
Pressure drop across the constriction:
As gas flows around the indicator it
encounters frictional resistance
between the indicator and tube
wall.there is loss of energy reflected in
a pressure drop. This pressure drop is
given by:
weight of float/cross sectional area

49. sSize of annular opening: The
annular area varies while the
pressure drop across the indicator
remains constant for all positions
in the tube for this reason there
are called as constant pressure
flowmeter.The elevation of
indicator is a measure of the
annular area of flow or the flow
itself
Physical characteristics of the gas:
Low Flow: Small annular space,
therefore flow is laminar,
therefore flow is a function of
gas viscosity . (Hagen-
poiseuille equation)

50. High Flow: Large annular
space, therefore flow is
turbulent, therefore the flow
depends on gas density .
(Graham,s law)

53. Flowmeters are calibrated at atmospheric
pressure (760 torr) and room temp( 20 deg C).
Changes in temp & pressure will affect density
and viscosity of a gas and affect flowmeter
accuracy.
In a hyperbaric chamber flowmeter will deliver
less gas than indicated .
With decreased barometric pressure (increased
altitude), the actual flow rate will be greater
than that indicated.

54. Arrangement
of flowmeter

55. AUXILIARY OXYGEN
FLOWMETER
Self contained flowmeter with its
own flow control valve,flow
indicator,& outlet
Short tube with maximum flow of
10L/min
Usually on the left side of the
machine
Can be used to supply O2 to patient
without turning ON the machine
Older machines – works on pipeline
supply,in newer ,works on cylinder
& pipeline supply both.

56. PROBLEMS WITH FLOWMETERS
Inaccuracy- if mixing of components
occur
Indicator problems – damage due to
sudden projection to top of the tube.
- worn or distorted
Leaks – if flow control valve is left
open, there is no cylinder or yoke plug
in the yoke
Using the wrong flowmeter – when
flowmeter sequence is altered

57. 62
Oxygen Supply Failure alarm
The standard machine specifies that whenever the
oxygen supply pressure falls below a manufacturer-
specified threshold (usually 30 psig) a medium priority
alarm shall blow within 5 seconds.
Electronic alarms: A pressure operated electric switch
operates this alarm
Ohmeda: 28 psig
Drager: 30-37 psig
Pneumatic alarms (aka Ritchie’s Whistle): Uses a
pressurized canister that is filled with oxygen when the
anesthesia machine is turned on. When the oxygen
pressure falls below a certain value, the alarm directs a
stream of oxygen through a whistle

58. Ritchie’s Whistle

59. OFPD
datex
ohmeda

60. OFPD
DRAGE
R

61. HYPOXIA PREVENTION SAFETY DEVICES
MANDATORY MINIMUM OXYGEN FLOW:
Some machines require a minimum ( 50-
250ml/min) flow of O2before other gas will flow
Some machines activate an alarm if O2flow goes
beyond a certain minimum.
MINIMUM OXYGEN RATIO:
Device to protect against operator selected
delivery of a mixture of O2& N2O having O2conc
below 21% O2.

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

63. Mechanical
linkage

64. LINK 25

65. Flow control valves are adjusted so that when 25%
O2 conc is reached ,a pin on O2sprocket engages a
pin on O2flow control knob.This causes O2& N2O
flow control valves to turn together to maintain
minimum O2of 25%.
If attempt is made to increase the N2O flow beyond
that ratio, the O2flow is automatically increased.
If O2flow is lowered too much the N2O flow is
decreased proportionally
An electronic system can be used to provide a
minimum ratio of O2to N2O flow
ALARMS:
Available to alert the operator that O2-N2O flow
ratio has fallen below a preset value

66. Leaks Downstream
Wrong Supply Gas
Defective Pneumatics or
Mechanics
LIMITATION

67. UNIDIRECTIONAL (CHECK )
VALVE
During controlled ventilation a positive
pressure from breathing circuit can be
transmitted back to the machine
Using O2flush valve may also cause this
Unidirectional check valves are present to
minimize these effects
Valve is located between vaporizers and
common gas outlet ,upstream of where O2
flush flow joins fresh gas flow

68. PRESSURE RELIEF VALVE
May be attached downstream of
vaporizers on the back bar itself
or near common gas outlet
Prevents high pressure being
transmitted to the machine
Whenever preset pressure is
exceeded valve opens to
atmosphere and gas is vented
outside
Usually opens when pressure in
the back 5 PSIG (300 cm of
H2O) This valve limits the
machine to provide jet
ventilation
Also known as the pop-off valve.

69. COMMON ( FRESH ) GAS
OUTLET
Receives all the gases and vapors
from the machine and delivers the
mixture to breathing system
Machine standard mandates that it
be difficult to accidentally
disengage the delivery hose from
the outlet
The pressure delivered at the outlet
is 5 -8 psi

70. BACK BAR
Part of frame of the Boyle’s machine which supports
the rotameter,vaporizers and other accessories
There are 2 metal rods in back bar
Flowmeters and vaporizers are connected with each
other and then bolted with the back bar.

71. VAPORIZER
A vapor is the gaseous phase of
substance that is liquid at room temp.
and atm. pressure
A vaporizer is an instrument designed
to change a liquid anaesthetic agent
into its vapor and add a controlled
amount of this vapor to fresh gas flow
As many as three vaporizer can be
attached to anaesthesia machine

72. Safety features
Pressure reducing valve
02 failure alarm
02,N20 link
Flourescent back panel
of rotameter
02 flush

73. Essential Features
• Noninterchangeable gas-specific
connections to pipeline inlets (DISS)1
with pressure gauges, filter, and check
valve
• Pin index safety system for
cylinders with pressure gauges, and
at least one
• oxygen cylinder
• Low oxygen pressure alarm
• Minimum oxygen/nitrous oxide
ratio controller device (hypoxic
Purpose
Prevent incorrect pipeline attachments;
detect failure, depletion, or fluctuation
Prevent incorrect cylinder attachments;
provide backup gas supply; detect
depletion
Detect oxygen supply failure at the
common gas inlet
Prevent delivery of less than 21%
oxygen

74. Oxygen failure safety device (shut-off or
proportioning device)
Prevent administration of nitrous
oxide or other gases when the
oxygen supply fails
Oxygen must enter the common manifold
downstream to other gases
Oxygen concentration monitor and alarm
Prevent hypoxia in event of
proximal gas leak
Prevent administration of hypoxic
gas mixtures in event of a low-
pressure system leak; precisely
regulate oxygen concentration
Prevent use of the machine without
essential monitors
Prevent simultaneous administration
of more than one volatile agent
Automatically enabled essential alarms and
monitors (eg, oxygen concentration)
Vaporizer interlock device

76. Capnography and anesthetic gas
measurement
Guide ventilation; prevent anesthetic
overdose; help reduce awareness
Oxygen flush mechanism that does not
pass through vaporizers
Breathing circuit pressure monitor and
alarm
Exhaled volume monitor
Rapidly refill or flush the breathing
circuit
Prevent pulmonary barotrauma and
detect sustained positive, high peak, and
negative airway pressures
Assess ventilation and prevent hypo- or
hyperventilation
Provide minimal standard monitoring
Pulse oximetry, blood pressure, and
ECG monitoring

77. Mechanical ventilator Control alveolar ventilation more
accurately and during muscle paralysis for
prolonged periods
Backup battery Provide temporary electrical power (> 30
min) to monitors and alarms in event of
power failure
Scavenger system Prevent contamination of the operating
room with waste anesthetic gases

80. THANK
S