An anesthesia workstation integrates components for anesthesia administration into one unit. It consists of an anesthesia machine, vaporizers, ventilator, breathing system, scavenging system, and monitors. Key components include the gas supply system, which receives gases from cylinders and pipelines and regulates pressures, and the vaporizer manifold and anesthetic vaporizers. Modern workstations have additional safety features to prevent delivery of hypoxic gas mixtures and other hazards.

1. DR ZIKRULLAH

2.  An anesthesia workstation integrates most of the components
necessary for administration of anesthesia into one unit.
 It consists of
• Anesthesia machine,
• Vaporizers,
• Ventilator,
• Breathing system,
• Scavenging system,
• Monitors.
 Added to this may be drug delivery systems, suction equipment,
and a data management system

3.  Original concept of Boyle's machine was invented by the
British anaesthetist HENRY BOYLE (1875–1941) in 1917.
Initial machines were either:
 Continuous flow – continuous flow throughout inspiration
and expiration (eg. Heidbrink, Foregger, Boyle)
 Intermittent flow – flow of gas during inspiration only (eg.
McKesson)

4. Boyle’s Anesthesia Apparatus
Modification of original machine developed by Dr. Henry Boyle in
1917

5. Foregger Metric Gas Machine
Montreal Model
• Modification of Richard von Foregger’s original metric gas
machine for use with cyclopropane

6. Water’s Cannisters
Ralph M Waters began experiments with CO2 absorption in 1915
Metal cylinder was packed with absorbent alkaline granules
resulting in economy of gas use along with heat and moisture
conservation

7. 119
 McKesson Nargraf Machine Heidbrink Apparatus
Midget Kinet-O-Meter

8. DRAGER FABIUS PLUS DATEX OHMEDA AESTIVA 5

9.  Monitoring and control functions as well as alarms can be
integrated and data displayed on a single or multiple screens.
 Reduced external connections should reduce the likelihood
of misconnections, disconnections, or kinked connections
 A certain amount of the preuse checking procedure can be
performed automatically.
 Built-in safeguards in case of machine failure

10.  Potential disruption of mechanical ventilation and gas delivery
 Display failure
 Electrical failure
 Fires
 Liquid spills
 May malfunction or act in a way that the anesthesia provider
does not recognize.

11.  Current standards - Standard Specification for Particular
Requirements for Anesthesia Workstations and Their
Components F1850-00, found within ASTM volume 13.02,
Medical and Surgical Materials and Devices.
 Additional key standards for machine subsystems arise from
the Compressed Gas Association (CGA) and the Institute of
Electrical and Electronics Engineers (IEEE)

12.  Recommendations for Pre-Anesthesia Checkout, which was
updated last in 2008, serves as a general guideline for
individual departments and practitioners to design
preanesthesia checkout procedures specific to their anesthetic
delivery systems

13. GAS SUPPLY SYSTEM can be divided functionally into:
 High-pressure section, involves the segments exposed to the
high pressures within the e-cylinder auxiliary gas tanks (e.g.,
≤2000 psig for air and oxygen)
 Intermediate-pressure section includes the segments exposed
to hospital pipeline pressures (50 to 55 psig)
 Low-pressure section in the range of 15 to 30 psig when
secondary pressure regulators are used

14.  Receives gases from cylinders at high, variable pressures and
reduces those pressures to lower, more constant pressure
suitable for use in the machine
 Auxiliary E-Cylinder Inlet- backup source of oxygen
 three and sometimes four points to accommodate oxygen,
air, and nitrous oxide
 cylinders are mounted to the anesthesia machine by the
hanger yoke assembly

15.  supports the cylinder, provides a gas-
tight seal, and ensures unidirectional
flow of gases into the machine
 Equipped with the Pin Index Safety
System (PISS )
 Critical to check the tank and yoke
labels also.

16.  Once a gas cylinder valve is opened by the operator, gas flows
first through a filter.
 Each cylinder supply source line have a pressure-reducing
mechanism known as the high-pressure regulator.
 Provide gas from the E-cylinders at a pressure of approximately
45 psig
 Then, gas flows through a one-way valve called the cylinder
check valve, prevents any backflow of machine gas

17.  On some older machines, the yoke
check valve is located before the high-
pressure regulator
 Auxiliary tank pressure gauges (or
electronic displays) must be located in
plain sight on the front of the
machine.
 Some electronic machines have
electronic transducers or light-
emitting diodes (LEDs) to indicate
cylinder pressure

18.  Close gas supply cylinder valves when not in use, except
during the preoperative machine checkout.
 If left open, the reserve cylinder supply can be silently
depleted

19. Pipeline inlet: hospital central gas supply
source
 Always enters the anesthesia machine
through diameter index safety system
(DISS) connectors
 Encounters a filter followed by a one way
pipeline check valve.
 Pipeline pressure must always be clearly
visible on the front of the machine.

20. Oxygen Flush Valve
 manual delivery of 100% oxygen directly to the patient’s
breathing circuit at a rate between 35 and 75 L/minute.
 available even when the machine is not turned on
 Barotrauma- in the fully open position
 Awareness- partially open position
 dilutes inhaled anesthetic agents.

21.  If oxygen supply pressure is reduced to below the
manufacturer specified minimum, the delivered oxygen
concentration shall not decrease below 19% at the common
gas outlet.”
Oxygen Supply Failure Alarm Sensor.
 Audible and visual warning
 Cannot be silenced

22.  Numerous types of pneumatic-electrical switches can serve
as this sensor.
 minimum threshold pressure for an alarm condition differs
among manufacturers and models.
 Dräger Narkomed machines had a set point of 37 psig
 Dräger Fabius series machines, are set to alarm at 20 psig

23.  Fail-safe valves shut off or
proportionally decrease the flow of
the other breathing gases
 When oxygen pressure is normal, it
will push the diaphragm and stem
downward, opening the valve.
 When the oxygen pressure falls, the
stem moves upward, closing the valve.

24.  low-flow oxygen for devices
independent of the breathing circuit.
 Accessible even when the machine is
turned off
 Allow use in the case of a system power
failure
 May serve as gas source for a jet
ventilation contraption

25.  located downstream from the gas supply sources
 supply constant pressure to the flow control valves
regardless of fluctuations in pipeline pressures.
 adjusted to lower pressure levels than the pipeline supply,
usually between 14 and 35 psig
Pneumatic component of master switch
Gas power outlet
Flow control valves

26. Key components include
 flowmeters or flow sensors
 vaporizer manifold
 anesthetic vaporizers.
 ends at the outlet of the fresh gas line
 most vulnerable section to leaks within the gas supply
system.

27.  Consists of a flow control knob, a
tapered needle valve, a valve seat, and
a pair of valve stops
 Inlet pressure determined by
intermediate-pressure segment
 Flow increases when valve is turned
counter clockwise, and vice versa

28.  Some newer machines have a fully digital control of flow
 Numerous types flow sensor technologies such as hot-wire
anemometers, a differential pressure transducer method, or
mass flow sensors
 Backup manual oxygen flow control and valve flowmeter
needed

29. Safety Features:
Oxygen flow control – knob
 Physically distinguishable from the other gas knobs.
 Color coded
 Chemical formula marked on each knob.
 Protected with a shield or barrier

30. Oxygen flow control valve is fluted and larger than the other flow control
valve. Also note the guard around each flow control valve. To the left of each
valve is the flow. At the left is a flowmeter for total flow.

31.  Mobile indicator float inside the
calibrated flow tube, that is free to
move vertically
 Indicates the amount of flow
passing through the associated
flow control valve.
 Variable orifice area flow tubes or
thorpe tubes

32.  Opening the valve allows gas to
travel through annular space
 Constant-pressure flowmeters
 Calibrated flow tubes are gas
specific.
 A stop at the top of the flowmeter
tube prevents the float from
occluding the outlet.

33.  Leakage: Flowmeters are located downstream from
antihypoxemia safety devices

34. Inaccuracy
 Dirt or static electricity can cause a float
to stick
 Damaged float
 Backpressure from the breathing circuit
 Flowmeters not aligned properly in the
vertical position

35.  Oxygen flow valves deliver a minimum flow of 150
mL/min when the anesthesia machine is turned on.
 Minimum flow resistor - ensure that some oxygen enters
the breathing circuit even if the operator forgets to turn
on the oxygen flow.
 Some machines deliver minimum flow or low-flow
anesthesia (< 1 L/min) and have minimum oxygen flows
as low as of 50 mL/min

36.  Most important pneumatic safety component
 Protect against an operator selected delivery of a mixture of
oxygen and nitrous oxide having below 21% oxygen (v/v%)
in the fresh gas or in the inspiratory gas.”
 Pneumatic-mechanical interface between the oxygen and
nitrous oxide flows or by mechanically linking the oxygen
and nitrous oxide flow control valves

38.  GE/Datex-Ohmeda Link-25 nitrous oxide: oxygen proportioning system. Prevents the
operator from selecting more than a 75% nitrous oxide–25% oxygen (3:1) mixture by two
separate but interdependent means. A, Mechanical linkage of the control valves
maintains no more than a 2:1 ratio. B, A faster taper of the nitrous oxide valve needle
allows more gas flow through the valve per turn relative to flow through the oxygen valve
per turn, thus resulting in the maximal 3:1 ratio. A stable and equal pressure by the
secondary pressure regulator for oxygen and a balance regulator for nitrous oxide

39. Delivery of hypoxic mixture under certain
conditions
 Wrong Supply Gas
 Leaks Downstream
 Dilution of Inspired Oxygen Concentration by Volatile
Inhaled Anesthetic Agents

40.  Vaporizer Mount allow for detachment
and replacement of the anesthetic
vaporizers by the workstation operator
 Vaporizer Interlock Devices prevent
fresh gas from flowing through more
than one vaporizer at time

41. Outlet Check Valve
 One way check valve located between the vaporizer and the
common gas outlet in the mixed-gas pipeline
 Prevent backflow into the vaporizer during positive-pressure
ventilation

42.  Modern variable bypass–type vaporizers are temperature
compensated
 Maintain desired outputs accurately over a wide range
input gas flow rates
 Modern vaporizers offer agent-specific keyed filling ports
to prevent filling with an incorrect agent
 Special desflurane vaporizers, the tec 6, tec 6 plus, and d-
tec (heated blender vaporizers)

43.  designed for use with the Datex-Ohmeda S/5 ADU and
similar machines.
 an agent-specific, color-coded, cassette

44.  Only one common gas outlet that supplies gas to the
breathing circuit.
 Unlike older models, some newer anesthesia machines
measure and report common outlet gas flows
 Antidisconnect device

45.  Most common- Circle System
 Bain circuit is occasionally used
 Newer anesthesia machines have
integrated internalized breathing circuit
components
 Reduced misconnects, disconnects,
kinks, and leaks.

46. Three types available:
 Polarographic (clark electrode),
 Galvanic (fuel cell)
 Paramagnetic
 Low-level alarm present , automatically activated by
turning on the anesthesia machine.
 Placed into the inspiratory or expiratory limb of the circle
system's breathing circuit

47.  used to measure exhaled tidal
volume in the breathing circuit,
typically near the exhalation valve.
 A common method employs a
rotating vane of low mass in the
expiratory limb in front of the
expiratory valve of the circle system

48.  Circuit Pressure- A pressure gauge or electronic sensor is
always used to measure breathing-circuit pressure
somewhere between the expiratory and inspiratory
unidirectional valves
 Adjustable Pressure-Limiting / pressure relief or pop-off
valve

50. PASSIVE HUMIDIFIERS
 simplest designs are condenser
humidifiers or heat and moisture
exchanger (HME)
 contain a hygroscopic material
that traps exhaled humidification,
which is released upon
subsequent inhalation.

51.  ACTIVE HUMIDIFIERS
 add water to gas by passing the gas
 heated humidifiers with thermostatically controlled
elements are most effective.

52.  early anesthesia ventilators - controlled mandatory ventilation
 Newer ventilators- multiple modes of ventilation
 act as a reservoir to receive and redeliver the patient’s exhaled
gas
 all modern ventilators are under electronic control
 Classification according to the type of reservoir that receives
and delivers the breathing gas (bellows, piston, or volume
reflector)

53. Pneumatically Driven Bellows Ventilator
 bellows serves as reservoir for the patient’s breathing gas.
 pressurized gas squeeze the gas out of bellows and back
to the patient
 excess circuit gas is vented to the scavenging system
during the expiratory pause
 double circuit, the ventilator drive gas and the breathing
gas exist in two separate circuits.

55.  Use a computer-controlled stepper motor to drive the
cylinder and actuate gas movement in the breathing
system
 Single-circuit ventilators
 Very accurate tidal volume delivery
 Computerized controls can provide advanced types of
ventilation support in addition to the conventional
control-mode ventilation

57.  Coiled, 3.6-m plastic channel with an approximate 1.2-L
capacity volume reflector
 Serves as reservoir for exhaled gases
 Reflector gas module is a solenoid-controlled oxygen flow
source
 Pushes the exhaled gas back out of the volume reflector during
inspiration through the carbon dioxide absorber to the patient

58.  FLOW-i system can compensate for breathing system
leaks by increasing reflector gas module flow
 Machine is nearly entirely electronically interfaced
 an emergency manual ventilation backup mode is
provided for cases of system failure

59.  Dispose of gases that have been
vented from the breathing circuit by
the APL valve and ventilator spill
valve.
 Both valves should be connected to
hoses (transfer tubing) leading to the
scavenging interface
 An “active system” uses a central
evacuation system to eliminate waste
gases.

60.  With a “passive system,” the pressure imposed by the venting
of the breathing circuit produces flow
 scavenging interface- open or closed.

61. Miscellaneous safety mechanisms
• Antistatic wheels and locking of wheels
• Backup battery
• Pressure relief valve
• Common gas outlet with retaining device to prevent
disconnection
• Provide temporary electrical power (> 30 min) to
monitors and alarms in event of power failure

62. ESSENTIAL FEATURES PURPOSE
Non-interchangeable gas specific
connections to pipeline inlets (DISS) with
pressure gauges, filter and check valve
Prevent incorrect pipeline attachments;
detect failure, depletion, or fluctuation
Pin Index Safety system for cylinders with
pressure gauges, and at least one oxygen
cylinder
Prevent incorrect cylinder attachments;
provide backup gas supply; detect
depletion
Low oxygen pressure alarm Detect oxygen supply failure at the
common gas inlet
Minimum oxygen/nitrous oxide ratio
controller device (hypoxic guard)
Prevent delivery of less than 21% oxygen
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
Prevent hypoxia in event of proximal gas
leak
IN A NUTSHELL…

63. Essential features Purpose
Oxygen concentration monitor and alarm Prevent administration of hypoxic gas
mixtures in event of a low-pressure system
leak; precisely regulate oxygen
concentration
Automatically enabled essential alarms
and monitors (e.g. oxygen concentration)
Prevent use of the machine without
essential monitors
Vaporizer interlock device Prevent simultaneous administration of
more than one volatile agent
Capnography and anaesthetic gas
measurement
Guide ventilation; prevent anaesthetic
overdose; help reduce awareness
Oxygen flush mechanism that does not
pass through vaporizers
Rapidly refill or flush the breathing circuit

64.  Individual anesthesia departments must align the ASA’s
recommendations for pre-anesthesia checkout
procedures with their respective manufacturers’ suggested
checkout procedures to develop their own effective,
workstation-specific PAC checklists

66. Regardless of who participates in the PAC, the anesthesia care
provider is ultimately responsible for the proper and safe
functioning of the equipment

67. DATEX OHMEDA AESPIRA 7100 DRAGER EVITA 500

68. FLOW I 40

69. THANK YOU