Anaesthesiology - for medical profession

1. UNDERSTANDING ANESTHESIA
WORKSTATION
Presenter: Dr. Viswanath, 3nd Sem.
Moderator: Dr. Deepika, SR
Consultant: Dr. Kayina Athiphro

2. Henry Edmund Gaskin Boyle- Introduced the First
Anesthesia Machine- Boyle’s Machine- 1917
A Continuous flow type machine used to deliver of inhalational
anesthetic agents

3. Modern Anesthesia workstation

4. How it differs from Boyles Machine?
• Boyle’s Machine has only pneumatic
component, where as Workstation has
Pneumatic ,Electric and Electronic
Components.
• Workstation has Intergrated Ventilators and
Monitors which lacks in Boyle’s machine.
• Workstation has Safety Features which is not
present in Boyles machine.

5. Today, anesthesia workstations are designed to do all of the
following:
• Deliver volatile anesthetic gas at precise concentrations.
• Individually meter oxygen and two or more other
breathing gases, and continuously enrich the inhaled gas
with anesthetic vapor.
• Allow the patient to be ventilated manually (“bag”
ventilation) with adjustable breathing circuit pressure.
• Ventilate the patient mechanically, with sophisticated
ventilator modes comparable to the intensive care unit
(ICU).
• Allow rebreathing of the exhaled anesthetic gases after
removing carbon dioxide.
• Eliminate (“scavenge”) excess gas from the patient’s
breathing circuit and remove this gas from the room.

6. • Continuously measure and display the inspired oxygen
concentration, as well as ventilatory parameters such
as respiratory rate and tidal volume.
• Prevent hypoxic gas mixtures caused by operator
error or gas supply failure.
• Provide a breathing circuit manual oxygen flush
feature.
• Possess a backup supply of oxygen.
• Display gas pipeline and backup tank supply pressures.
• Provide an integrated platform for displaying
anesthetic, hemodynamic, and respiratory parameters
and for collecting this data into an electronic medical
record.

7. • If there is any possibility that the workstation or the breathing
circuit is potential cause of difficulty with ventilation or
oxygenation, switching to self inflating resuscitation bag is an
appropriate decision.
- Miller’s Anesthesia.
• “Ventilate and oxygenate first – troubleshoot later”
• The most important part of the pre-use anesthesia
workstation checkout procedure is verifying the
presence of a self-inflating resuscitation bag and E-
cylinder .

8. • The anesthesia machine is a complex piece of equipment
consisting of vaporizers, a ventilator, breathing and
scavenging systems, and monitors.
• There are two general systems comprising the anesthesia
machine:
Electrical component
Pneumatic component

9. Parts of Electrical Component
• Master switch
• Power Failure Indicator
• Reserve Power
• Electrical Outlets
• Circuit breakers
• Data communication ports

10. I. ELECTRICAL COMPONENTS
1) MASTER SWITCH:
• A master (main power) switch activates both the pneumatic and
electrical functions.
• On most machines, when the master switch is in the OFF position,
the only electrical components that are active are the backup
battery charger and the electrical outlets.

11. • In most cases, a machine must be turned OFF and the
computer rebooted at least every 24 hours to clear previously
stored start-up data.
• Failure to do this could cause the computer to malfunction.
User manual must be checked for the recommendations for
that particular machine.

12. 2) Power Failure Indicator:
• Most machines are equipped with a visual and/or audible indicator to
alert the anesthesia provider to the loss of mains electrical power
Clinical Moments:
• If the power indicator shows loss of mains electrical power or that the
battery is in use, first check that the power line has not become loose or
disconnected. Do what you can to conserve electrical energy until the
problem is fixed.

13. 3) Reserve Power:
• Since electricity is crucial for most anesthesia machines,
a backup source is provided. Generally, this will provide
power for 30 minutes, depending on usage.
• A noninterruptible power source may be added to the
anesthesia machine to extend the backup period.

14. 4) Electrical Outlets:
• Most modern anesthesia machines have electrical outlets at the back of
the machine. These are intended to power monitors and other anesthesia
devices. They usually cannot supply electricity if there is a power failure.
Clinical Moments:
• These outlets should not be used to power anything other than
anesthesia devices and must not be used to power other devices such as
operating room tables, floor vacuums, or electrosurgical units.

15. II. Pneumatic components
High
Pressure
System
Intermediate
Pressure
System
Low
Pressure
System

18. PRESSURE SYSTEMS
• High
- Confined to cylinders and cylinder primary pressure
regulators
O2 – 2200 psig 45psig
N2O – 750 psig 45 psig
• Intermediate
- Begins at pressure regulated cylinder supply source at
45 psig, include the pipeline source of 50-55 psig and
extends to flow control valves
• Low
- Extends from the flow control valves to the common as
outlet
(5-8 Psig) Just above atmospheric pressure and variable

19. O2 2200→ 45 Psig
N2O 750→45 Psig
50-60 Psig

20. 1. High Pressure System –
Receives gases from cylinders at high, variable pressures and reduces those
pressures to a lower, more constant pressure suitable for use in the machine.
Cylinder- Hanger
yoke assembly
Check valves
Cylinder Pressure
Gauge (Indicator)
Pressure
Regulator

21. Cylinders
-Seamless (No Joins in cylinder)–
to Withstand high pressure inside.
- Made of Molybdenum:
High Tensile strength
Light weight
- Aluminium cylinders for
MRI suites.
3AA- Steel
3AL or 3ALM - Aluminium

22. OXYGEN CYLINDER NITROUS CYLINDER

24. 1949
New International
Color coding from
2010- Not followed
in India yet

25. Safety Feature of Cylinders
1. Made of Molybdenum steel – high tensile
strength
2. Colour coding
3. Seamless body
4. Safety relief valve
5. Pin index safety system

27. Pin Index Safety System- Philip
Woodbridge (1952)

29. Pressure relief device
• For venting of high pressure gases from inside the
cylinder (safety system).
• Types:
-Rupture disc – copper
-Fusible plug
-Combination of both
-Pressure relief valve(spring loaded)

30. Fusible Plug
• Made of Woods Alloy-
- Cadmium
- Bismuth
- Lead
- Tin
- (Melts at 150-170 deg)

32. i) Hanger Yoke:
• The hanger yoke orients and supports the cylinder, provides a gas-
tight seal, and ensures a unidirectional gas flow.
• It is composed of several parts:
• The body, which is the principal framework and supporting
structure;
• A retaining screw, which tightens the cylinder in the yoke;
• A nipple, through which gas enters the machine;
• Pin Index Safety System pins which prevent an incorrect cylinder
from being attached;
• A washer, which helps to form a seal between the cylinder and the
yoke;
• A filter to remove particulate matter that could come from the
cylinder.

33. Hanger Yoke Assembly

34. Functions of Hanger Yoke Assembly
• Supports and orients the cylinder to this
machine.
• Maintains leak proof connection between
cylinder and the machine.
• Maintains unidirectional flow of gases towards
the machine.(check valve)

36. Cylinders Should be opened Slowly.
Why?

37. ii) Check Valve
• The check valve allows gas from a cylinder to
enter the machine but prevents gas from exiting
the machine when there is no cylinder in the
yoke.
• It allows an empty cylinder to be replaced with a
full one, without losing gas from other cylinders
of the same gas that are open or from the
intermediate pressure system.
• The check valve also prevents gas from being
transferred from a cylinder with a higher pressure
to another one with a lower pressure when both
are connected to a double yoke and opened at
the same time.

39. Clinical Moments:
• A yoke should not be left vacant. As soon as a cylinder is
exhausted, it should be replaced by a full one. If a full cylinder
is not available, a yoke plug (dummy cylinder block or plug,
blanking cap or plug) should be placed in the empty yoke.
• The yoke plug is a solid piece of metal which fits over the
nipple.
• When in place, the plug forms a seal to prevent the gas from
escaping from the machine. Manufacturers often chain yoke
plugs to the machine.

41. Clinical Moments:
• When placing a cylinder in a yoke, it is important that the
cylinder valve and yoke not be contaminated with oil or
grease, because this could cause a fire .The person placing
a cylinder in a yoke should always wash his/her hands first.
• Before a cylinder is mounted in place, the yoke should be
checked for the two Pin Index Safety System pins are
present. A missing pin could allow the safety system to be
bypassed.
• After the cylinder has been tightened onto the yoke, it
should be opened to make certain that the cylinder is full
and that there is no leak (as evidenced by a hissing sound).
The most common cause of a leak is a defective or missing
washer. If the cylinder valve leaks or is difficult to operate,
the cylinder should be returned to the supplier.

42. Clinical Moments:
• After the cylinder has been attached to the yoke, the
valve should be closed unless it is to be the primary
gas supply for the machine.
• If the pipeline is the primary supply and the valve
remains open, fluctuations in the gas pressure in the
machine could allow some or all of the gas to exit the
cylinder.
• In the event that pipeline pressure is lost, gas could be
used from the cylinder without the user being aware
of the change. The first time that the user becomes
aware of the lost pipeline pressure could be when the
cylinder becomes empty.
• If only one gas cylinder is present, there would be no
gas available.

43. iii) Cylinder Pressure Gauge (Indicator):
• Many cylinder pressure gauges (indicators) are the Bourdon tube
(Bourdon spring, elastic element) type.
• A hollow metal tube is bent into a curve and then sealed and linked
to a clocklike mechanism. The other end is connected to the gas
source.
• An increase in gas pressure inside the tube causes it to straighten.
As the pressure falls, the tube resumes its curved shape. These
motions are transmitted to the indicator, which moves over a
calibrated scale.
• A drawback of these mechanical pressure gauges is that their
readings cannot be transferred to a data management system.
• Most new anesthesia machines indicate cylinder pressure digitally.
• Light-emitting diodes may also be used to indicate adequate
pressure in the cylinder.

44. Bourdon’s Pressure Gauge

47. • iv) Pressure Regulator:
• A pressure regulator reduces the high and variable pressure
delivered from a cylinder to a lower, more constant pressure
suitable for use in an anesthesia machine.
• Without a regulator, it would be necessary for the anesthesia
provider to constantly alter the flow control valve to maintain a
constant flow through the flowmeter as the pressure in the cylinder
decreases.
• The pressure at the regulator outlet is set lower than the pipeline
pressure.
• This ensures that pipeline gas is used preferentially to the cylinder
supply if the cylinder valve is open while oxygen from the piping
system is being used. This differential pressure may not always
prevent the cylinder from becoming exhausted since pressure
fluctuations in the pipeline may cause the pressure in the machine
to drop below the pressure from the pressure regulator.

48. INTERMEDIATE
PRESSURE
SYSTEM

49. About Intermediate Pressure System
• The Intermediate –pressure system extend from the
pipelines or from stepped –down input from the E-
cylinders and extends up to the flow control valves.
• It receives gases from the pressure regulator or the
pipeline inlet at 40-55 psig.
It consists of :-
 Pneumatic part of the master switch
 Pipeline inlet connections
 Pipeline pressure indicators
 Piping
 The gas power outlet
 Oxygen pressure failure devices
 Oxygen flush
 Flow control valves
 Alternative Oxygen source

50. Master switch
( pneumatic component )
• The pneumatic portion of the master switch is
located in the intermediate pressure system
downstream of the inlets for the cylinder and
pipeline supplies.
• The Oxygen flush is usually independent of
this switch .
• When the master switch is turned off , the
pressure in the intermediate pressure system
will drop to zero.

51. Quick couplers
 Pipelines have couplers to connect to the
source.
 These are color coded and have pins in
different configurations.
 Quick couplers utilize pins and
corresponding slots on the male & female
ends, respectively.

52. Quick couplers(Cont.)

53. PIPELINE INLET CONNECTIONS

54.  DISS is a threaded connection in
which the diameter and shape of
each thread is specific for each
gas.
PIPELINE INLET CONNECTIONS

55. Pipeline Pressure Indicators

56. Pipeline Pressure Indicators

57. Oxygen Failure Safety Devices

58. Pressure Sensor Shut Off Valve
 Based on threshold principle
 Cuts off N2O supply when O2
pressure falls below 25 psi.
 MOA-O₂ pressurises and
holds open shut off valve that
interrupts the supply of N2O
and other gases if O2
pressure < threshold setting.
Oxygen supply Failure Protection
Device
 Based on proportioning principle
 Gas loaded regulator
 When O₂ pressure decreases there is
a proportional decrease in N2O
supply and complete cut off seen
at<12psi.
 MOA-O₂ pressure regulator(primary
regulator) controls secondary(slave)
regulator located in N₂O line
Oxygen Failure Safety Devices

59. Oxygen Supply Failure Alarm

60. Oxygen Flush valve (O2+)

61. Oxygen Flush valve (O2+)

62. Alternative Oxygen Control

63.  The mechanical flow control valves utilizes a stem with fine threads that when
turned clockwise will move inward to decrease or stop gas flow
 When turned counterclockwise the stem will move outward to increase the gas
flow .
Flow control valves

64. Flow control valves

65. LOW
PRESSURE
SYSTEM

66. LOW PRESSURE SYSTEM

67.  When the flow control valve is opened
the gas enters at.the bottom and flows
up the tube elevating the indicator
 Transparent flow tube known as a
variable orifice flowmeter or Thorpe
tube.
 Thorpe Tube is made up of Pyrex glass,
transparent, nonconducting material .
 It is conical in shape ,tapered vertically
with smallest diameter at the bottom
 INDICATOR ( FLOAT OR BOBBIN)
 It is light weight , made up of
aluminium .It contains antistatic
material to prevent sticking to wall of
flowmeter .
 The indicator floats freely at a point
where the downward force on it
(gravity) equals the upward force
caused by gas molecules hitting the
bottom of the float
FLOW CONTROL ASSEMBLIES

68. FLOW CONTROL ASSEMBLIES

69.  The knobs are specifically
designed for each gas.
 This is a safety feature to assist in
low light conditions.
FLOW CONTROL ASSEMBLIES

70.  In the presence of a
flowmeter leak (either at the
“O” ring or the glass of the
flow tube) a hypoxic
mixture is less likely to
occur if the O2 flowmeter is
downstream of all other
flowmeters.
 In A and B a hypoxic
mixture can result because a
substantial portion of
oxygen flow passes through
the leak, and all nitrous
oxide is directed to the
common gas outlet
Arrangement of the Flow-Indicator Tubes

71. AUXILLARY OXYGEN FLOWMETER

72. ANTI HYPOXIA DEVICES

73. Hypoxia Prevention Safety Devices
MECHANICAL

74. Hypoxia Prevention Safety Devices

75. Hypoxia Prevention Safety Devices

76. Oxygen ratio monitor controller
Sensitive oxygen ratio controller
 Linear resistors (3:1 ratio for N₂O & O₂)between
O₂ and N₂O flow control valves.
 Ensure 25% O₂ by limiting N₂O flow.
 ORMC shuts off N₂O if ratio of O₂ flow falls
below 30%.
 S-ORC-newest hypoxic guard. Installed in
Fabius- GS by Drager. Ensures a FiO₂ of 23%.
O₂ flow <200ml/min
Hypoxia Prevention Safety Devices
PNEUMATIC [ ORMC ( DRAGER ) ]

77. Hypoxia Prevention Safety Devices
ELECTRONIC
Electronic devices e.g.PENLON use a paramagnetic
oxygen analyser to continuously sample the gas mixtures
from the flowmeters .
 In this the nitrous oxide gets temporarily shut off when
the inspired fraction of oxygen (FiO2 ) decreases below
0.25, while a increase in the FiO2 will temporarily start
the nitrous oxide flow .

78. UNIDIRECTIONAL (CHECK) VALVE

79. PRESSURE RELIEF VALVE

80. 80
COMMON (FRESH) GAS OUTLET

81. PRE-
ANESTHESIA
CHECKOUT
PROCEDURES

82. 82
PRE-ANESTHESIA CHECKOUT PROCEDURES

83.  1. Verify Auxiliary Oxygen Cylinder and Self- Inflating
Manual Ventilation Device Are Available and
Functioning
83
Workstation checkout procedure
 2. Verify Patient Suction Is Adequate to Clear the
Airway
3.Turn on Anesthesia Delivery System and Confirm
That AC Power Is Available.

84.  4.Verify Availability of Required Monitors and Check Alarms
 Monitoring supplies ( BP cuffs of appropriate sizes, pulse oximetry
probes , Pulse oximeter and capnography )
84
 5.Verify That Pressure Is Adequate on the Spare Oxygen Cylinder
Mounted on the Anesthesia Machine
 6.Verify That Pipeline Gas Pressures Are 50 psig or Higher

85.  7.Verify That Vaporizers Are Adequately Filled and, If Applicable, That
the Filler Ports Are Tightly Closed
 Check of their machine’s vaporizer interlock system ,which , if present , prevent
more than one vaporizer from being activated simultaneously.
85
Test for Vapouriser

86. 8. Universal Leak Test
 Verify That No Leaks Are Present in the Gas Supply Lines Between the
Flowmeters and the Common Gas Outlet
 It is Highly sensitive, detecting leaks as small as 30 mL/min
86

87. 87
9. Test Scavenging System Function
 Evaluation of scavenging system is a manual maneuver.
 No automated checks are conducted.
 A test of the scavenging system begins by checking the proper assembly and integrity
of each component and connection within the system

88. 12. Breathing System Pressure and Leak Testing
 10. Calibrate, or Verify Calibration of, the Oxygen Monitor and Check the
Low Oxygen Alarm
 Function of the low-oxygen concentration alarm should be tested daily
 Manually setting the low oxygen concentration alarm limit to more than 21%
while exposing the analyzer to room air, generating the alarm condition
88
11. Verify Carbon Dioxide Absorbent Is Not Exhausted

89. 8
9
12. Breathing System Pressure and Leak Testing

90.  Test of circuit flow is accomplished by placing a “test lung” or an extra breathing
bag at the patient Y-piece.
 In the “bag” or a manual mode of ventilation, the operator ventilates the artificial
“lung” with the breathing bag, then actively “exhales” (squeezes) the test lung
back to the breathing bag in a to-and-fro motion. This is the so-called flow test.
9
0
13. Verify That Gas Flows Properly Through the Breathing Circuit
During Both Inspiration and Exhalation

91. 9
1
14. Document Completion of Checkout Procedures

92. 9
2
The MS MAIDS checklist