? The Anesthesia gas machine is a device which delivers a
precisely known but variable gas mixture, including
--- Content provided by FirstRanker.com ---
anesthetizing and life sustaining gases.
Objective
?Become familiar with the basic design of an anesthetic machine
--- Content provided by FirstRanker.com ---
? Become familiar with the design and functioning of anestheticvaporizers.
?Become familiar with the design and functioning of the more
--- Content provided by FirstRanker.com ---
commonly used breathing circuits
History
--- Content provided by FirstRanker.com ---
before the invention of anaesthesia...surgery was an agony...a nightmare....
--- Content provided by FirstRanker.com ---
Boyle's Apparatus- 2000s
Modern anaesthesia workstation
Types of Anaesthesia Machine
--- Content provided by FirstRanker.com ---
? INTERMITTENT - Gas flow only during inspiration
- Entonox appartus, Mackessons
? CONTINUOUS - Gas flows both during inspiration and expiration
- Boyle machine , forregar , dragger
--- Content provided by FirstRanker.com ---
Components of anaesthesia machine
? Comprise of three different pressure systems-
? High pressure system: from cylinder to pressure reducing valves
--- Content provided by FirstRanker.com ---
? Intermediate pressure system: from pressure reducing valves toflowmeters
? Low pressure system: from flow meters to the common gas outlet on
--- Content provided by FirstRanker.com ---
machine
High pressure system
--- Content provided by FirstRanker.com ---
n Receives gasses from the high pressure E cylindersattached to the back of the anesthesia machine
(2200 psig for O2, 745 psig for N2O)
--- Content provided by FirstRanker.com ---
n Consists of:
? Hanger Yolk (reserve gas cylinder holder)
? Check valve (prevent reverse flow of gas)
--- Content provided by FirstRanker.com ---
? Cylinder Pressure Indicator (Gauge)? Pressure Reducing Device (Regulator)
n Usually not used, unless pipeline gas supply is off
Components of high pressure system
--- Content provided by FirstRanker.com ---
? Hanger yoke: orients and supports cylinder, provides a gas tight seal, ensuresunidirectional gas flow. Parts of hanger yoke assembly are:
? Body: principal framework of yoke, attached to body of machine
--- Content provided by FirstRanker.com ---
? Retaining screw: its threaded into distal end of yoke, fits into conical depression ofcylinder valve and yoke
? Nipple: gas enters machine through nipple
--- Content provided by FirstRanker.com ---
? Index pin: are below the nipple? Washer/Bodok seal: Placed around nipple to produce seal between cylinder valve
and yoke.
--- Content provided by FirstRanker.com ---
? Filter: filters 100m particulates? Check valve assembly: allows gas from cylinder to enter machine but not vice versa
A. Cylinder yokes. The empty right-hand yoke shows a Bodok seal and the pins of the
--- Content provided by FirstRanker.com ---
pin index system.B. Diagram of cylinder yoke assembly
Pin-Index safety system-1952
? Safety mechanism so that one cylinder can not be fitted at the other's
--- Content provided by FirstRanker.com ---
position
? It consists of holes on the cylinder valve and two pins on the yoke
--- Content provided by FirstRanker.com ---
positioned to fit into the holes? Pins are 4 mm in diameter and 6 mm long (except pin-7)
? The 7 hole positions are on the circumference of a circle of 9/16 inch
--- Content provided by FirstRanker.com ---
radius centred on the port.? Six pin positions are located at an interval of 12 degree, with pin 7
located between 3 and 4.
--- Content provided by FirstRanker.com ---
Pin-index system
Bourdon Pressure Gauge
? Must be clearly marked with: Name or
--- Content provided by FirstRanker.com ---
chemical symbol of gas color assigned to
gas
--- Content provided by FirstRanker.com ---
? Each hanger yoke or group ofinterconnected yokes should be supplied
with pressure indicator to display pressure
--- Content provided by FirstRanker.com ---
of cylinder supplied gas.
? If indicator is circular , the lowest pressure
--- Content provided by FirstRanker.com ---
indication should be between 6 o' clock and9 o' clock position on clock face.
? Scale must be 33% more than maximum
--- Content provided by FirstRanker.com ---
filling pressures.
Pressure reducing devices
? Pressure in cylinder varies to maintain constant flow, with changing
--- Content provided by FirstRanker.com ---
supply pressure regulators are provided
? Reduces high and variable pressure found in cylinder to a lower and
--- Content provided by FirstRanker.com ---
more constant pressure found in the anaesthesia machine (40-45psig)
Intermediate Pressure System
--- Content provided by FirstRanker.com ---
q Receives gasses from the regulator or the
hospital pipeline at pressures of 40-55 psig
q Consists of:
?Pipeline inlet connections
--- Content provided by FirstRanker.com ---
?Pipeline pressure indicators?Piping
?Gas power outlet
?Master switch
?Oxygen pressure failure devices
--- Content provided by FirstRanker.com ---
?Oxygen flush?Additional reducing devices
?Flow control valves
Pipeline Inlet Connections
--- Content provided by FirstRanker.com ---
? Mandatory N2O and O2, usuallyhave air and suction too
? Inlets are non-interchangeable
--- Content provided by FirstRanker.com ---
due to specific threading as per
the Diameter Index Safety
--- Content provided by FirstRanker.com ---
System (DISS)? Each inlet must contain a check
valve to prevent reverse flow
--- Content provided by FirstRanker.com ---
(similar to the cylinder yoke)
DISS
Terminal outlets. Note the different diameter recesses (collar indexing
--- Content provided by FirstRanker.com ---
system) that match the collar on
the relevant probe
--- Content provided by FirstRanker.com ---
Flexible hoseprobes. Note the
difference in size
--- Content provided by FirstRanker.com ---
of the indexing
collar
--- Content provided by FirstRanker.com ---
Colour-coded hoses.Oxygen Pressure Failure Devices
? The oxygen concentration at the common gas
--- Content provided by FirstRanker.com ---
outlet does not fall below 19%.? A Fail-Safe valve is present in the gas line
supplying each of the flowmeters (except O 2)
--- Content provided by FirstRanker.com ---
? This valve is controlled by the O2 supply
pressure and shuts off or proportionately
--- Content provided by FirstRanker.com ---
decreases the supply pressure of all othergasses as the O2 supply pressure decreases
? Historically there are 2 kinds of fail-safe valves
--- Content provided by FirstRanker.com ---
? Pressure sensor shut-off valve (Ohmeda)? Oxygen failure protection device (Drager)
Oxygen Supply Failure Alarm
--- Content provided by FirstRanker.com ---
? The machine standard specifies that whenever the oxygen supply pressurefalls below a manufacturer-specified threshold (usually 30 psig) a medium
priority alarm shall blow within 5 seconds.
--- Content provided by FirstRanker.com ---
? Electronic alarms: A pressure operated electric switch operates this alarm\
? Ohmeda: 28 psig
? Drager: 30-37 psig
--- Content provided by FirstRanker.com ---
? Pneumatic alarms (Bowman's Whistle): Uses a pressurized canister that isfilled with oxygen when the anesthesia machine is turned on. When the
oxygen pressure falls below a certain value, the alarm directs a stream of
--- Content provided by FirstRanker.com ---
oxygen through a whistle
Oxygen Flush Valve (O2+)
? Receives O2 from pipeline inlet or cylinder reducing device and
--- Content provided by FirstRanker.com ---
directs high, unmetered flow directly to the common gas outlet
(downstream of the vaporizer)
--- Content provided by FirstRanker.com ---
? Machine standard requires that the flow be between 35 and 75 L/min? The ability to provide jet ventilation via the O2 flush valve is presence
of a check valve between the vaporizer and the O2 flush valve
--- Content provided by FirstRanker.com ---
(otherwise some flow would be wasted retrograde)qHazards:
?May cause barotrauma
?Dilution of inhaled anesthetic
--- Content provided by FirstRanker.com ---
? Flush valves for gases other than oxygen are not permitted.
? Oxygen flush can be activated regardless of whether machine is
--- Content provided by FirstRanker.com ---
turned ON or OFF.? Protective rim is present which prevents unintentional
activation
--- Content provided by FirstRanker.com ---
Master switch? Turning the master switch to the `on' position
? activates both pneumatic and electrical
? functions of the machine as well as certain
--- Content provided by FirstRanker.com ---
? alarms and safety devices.Second-Stage Reducing Device
? Located just upstream of the flow control valves
--- Content provided by FirstRanker.com ---
? Receives gas from the pipeline inlet or the cylinder reducing deviceand reduces it further to 26 psig for N2O and 14 psig for O2
? Purpose is to eliminate fluctuations in pressure supplied to the flow
--- Content provided by FirstRanker.com ---
indicators caused by fluctuations in pipeline pressure
Flow/ Control valves (Needle Valves/ Pin Valves/
Fine Adjustment Valves/ Flow adjustment controls
--- Content provided by FirstRanker.com ---
? Controls rate of flow of gas through its associated flow indicator bymanual adjustment of a variable orifice.
? Current standard requires that there be only one flow control valve
--- Content provided by FirstRanker.com ---
for each gas. It must be adjusted or identifiable with it's flow indicator
Components
--- Content provided by FirstRanker.com ---
? Body.-Screwed to the base of flow indicator
? Stem and Seat.
--- Content provided by FirstRanker.com ---
? Control knob.Low Pressure System
? Extends from the flow control valves to the common gas outlet
--- Content provided by FirstRanker.com ---
? Pressure is only slightly above atmospheric pressure.? Consists of:
? Flow meters
? Vaporizer mounting device
? Check valve
--- Content provided by FirstRanker.com ---
? Back pressure safety devices (Pressure relief device)? Common gas outlet
Flowmeter tubes
--- Content provided by FirstRanker.com ---
? Measures and indicates RATE OF FLOW of gas .? TYPES:
? Constant-pressure variable-orifice type
? Electronic flowmeter
Constant-pressure variable orifice
--- Content provided by FirstRanker.com ---
flowmeter
? Measures drop in pressure that occurs when gas passes
through resistance
--- Content provided by FirstRanker.com ---
? Correlates this pressure ?drop to flow
Flowmeter assembly
--- Content provided by FirstRanker.com ---
? When the flow control valve isopened the gas enters at the bottom
and flows up the tube elevating the
--- Content provided by FirstRanker.com ---
indicator
? The indicator floats freely at a point
--- Content provided by FirstRanker.com ---
where the downward force on it(gravity) equals the upward force
caused by gas molecules hitting the
--- Content provided by FirstRanker.com ---
bottom of the float
? Because the tube is tapered the
--- Content provided by FirstRanker.com ---
annular opening around the indicatorincreases with height and more gas
flows around the float
--- Content provided by FirstRanker.com ---
Parts of flowmeter assembly? Tube
? Float/Bobbin
? Stop at top of tube
--- Content provided by FirstRanker.com ---
? Scale? Plastic shields
? Lights
? Each flowmeter assembly should be permanently identified with:
? Color of gas
--- Content provided by FirstRanker.com ---
? Chemical symbol / Name of gasTube
? Made of glass
--- Content provided by FirstRanker.com ---
? Gas passes between bobbin and inner wall of tube? Tapered
? Flow increases from below upward
? Also known as `Thorpe' tube
Electronic flowmeter
--- Content provided by FirstRanker.com ---
Prefer digital system
? Solenoid valves
--- Content provided by FirstRanker.com ---
? Control flow on orof valves
? Computer
--- Content provided by FirstRanker.com ---
controlled
Auxiliary oxygen flowmeter
Anti-hypoxia devices
--- Content provided by FirstRanker.com ---
? Mechanical devices- "Link-25 system"
? Pneumatic device- "ratio-mixer valve"
? Electronically controlled device- "penlon ltd"
Vaporizers
--- Content provided by FirstRanker.com ---
? A vaporizer is an instrument designed to change a liquid anestheticagent into its vapor and add a controlled amount of this vapor to the
fresh gas flow
--- Content provided by FirstRanker.com ---
Common gas outlet? Receives all gases and vapors from machine.
? Most machine outlets have 15mm female connection with coaxial
--- Content provided by FirstRanker.com ---
22mm male connection.? Miscellaneous : Antistatic wheels
? This list is by no means exhaustive and newer anaesthesia machines
--- Content provided by FirstRanker.com ---
have incorporated a lots of new features to enhance the safety.
Breathing system
--- Content provided by FirstRanker.com ---
? A breathing system is defined as an assembly of components whichconnects the patient's airway to the anaesthetic machine creating an
artificial atmosphere, from and into which the patient breathes
--- Content provided by FirstRanker.com ---
? Purpose? To deliver anesthetic gases and oxygen
? Offer a means to deliver anesthesia without significant increase in
airway resistance
--- Content provided by FirstRanker.com ---
? To offer a convenient and safe method of delivering inhaled
anesthetic agents
--- Content provided by FirstRanker.com ---
? Components? A fresh gas entry port / delivery tube
? A port to connect it to the patient's airway;
? A reservoir for gas, in the form of a bag
? An expiratory port / valve
--- Content provided by FirstRanker.com ---
? A carbon dioxide absorber if total rebreathing is to be allowed? Corrugated tubes for connecting these components.
? Flow directing valves may or may not be used.
? Requirements of a Breathing System
? Essential:
--- Content provided by FirstRanker.com ---
? The breathing system must deliver the gases from the machine to thealveoli in the same concentration as set and in the shortest possible
time;
--- Content provided by FirstRanker.com ---
? Effectively eliminate carbon-dioxide;
? Have minimal apparatus dead space; and
? Have low resistance.
--- Content provided by FirstRanker.com ---
vRequirements of a Breathing System? Economy of fresh gas;
? Conservation of heat;
? Adequate humidification of inspired gas;
? Light weight;
--- Content provided by FirstRanker.com ---
? Convenience during use;? Efficiency during spontaneous as well as controlled ventilation
adaptability for adults, children and mechanical ventilators;
--- Content provided by FirstRanker.com ---
? Provision to reduce theatre pollutionTable 1. Classification of breathing systems
Classification Of Breathing Systems
--- Content provided by FirstRanker.com ---
BREATHING SYSTEMS WITHOUT CO2 ABSORPTION.BREATHING SYSTEMS WITH CO2 ABSORPTION.
Unidirectional flow:
--- Content provided by FirstRanker.com ---
Unidirectional flow
a) Non rebreathing systems.
--- Content provided by FirstRanker.com ---
Circle system with absorber.B) Circle systems.
--- Content provided by FirstRanker.com ---
--- Content provided by FirstRanker.com ---
Bi-directional flow:Bi-directional flow
a) Afferent reservoir systems.
--- Content provided by FirstRanker.com ---
To and Fro system.
Mapleson A
--- Content provided by FirstRanker.com ---
Mapleson B
--- Content provided by FirstRanker.com ---
Mapleson C
Lack's system.
--- Content provided by FirstRanker.com ---
B) Enclosed afferent reservoir systemsMiller's (1988)
c) Efferent reservoir systems
--- Content provided by FirstRanker.com ---
Mapleson D
Mapleson E
--- Content provided by FirstRanker.com ---
Mapleson FBain's system
d) Combined systems
--- Content provided by FirstRanker.com ---
Humphrey ADE
--- Content provided by FirstRanker.com ---
Mapleson D? 3 phases of respiration
1) Inspiration
2) Expiration
--- Content provided by FirstRanker.com ---
3) End-expiratory pauseBain's system
? Coaxial (tube within a tube) version of
Mapleson D
--- Content provided by FirstRanker.com ---
? Fresh gas enters through narrow inner
tube
--- Content provided by FirstRanker.com ---
? Exhaled gas exits through corrugatedouter tube
? FGF required to prevent rebreathing:
--- Content provided by FirstRanker.com ---
-200-300ml/kg/min withspontaneous breathing (2 times V E )
-70ml/kg/min with controlled
--- Content provided by FirstRanker.com ---
ventilationCircle system
v Breathing Systems with CO2 Absorption
--- Content provided by FirstRanker.com ---
- Sodalime canister,- Two unidirectional valves,
- Fresh gas entry, Y-piece to connect to the patient,
- Reservoir bag a relief valve and
- Low resistance interconnecting tubing.
--- Content provided by FirstRanker.com ---
Circle systemCircle system
v 3 Essential Factors
--- Content provided by FirstRanker.com ---
? There should be two unidirectional valves on either side of thereservoir bag and the canister ,
? Relief valve should be positioned in the expiratory limb only,
--- Content provided by FirstRanker.com ---
? The FGF should enter the system proximal to the inspiratoryunidirectional valve
Circle system
--- Content provided by FirstRanker.com ---
vOptimization of Circle Designq Unidirectional Valves
?Placed in close proximity to patient to prevent backflow into
inspiratory limb if circuit leak develops.
--- Content provided by FirstRanker.com ---
qFresh Gas Inlet
?Placed between absorber & inspiratory valve. If placed downstream
from inspiratory valve, it would allow FG to bypass patient during
--- Content provided by FirstRanker.com ---
exhalation and be wasted. If FG were placed between expiration valve
and absorber, FG would be diluted by recirculating gas
--- Content provided by FirstRanker.com ---
Circle systemvOptimization of Circle Design
qAPL valve
? Placed immediately before absorber to conserve absorption capacity
--- Content provided by FirstRanker.com ---
and to minimize venting of FG
qBreathing Bag
? Placed in expiratory limb to decrease resistance to exhalation. Bag
--- Content provided by FirstRanker.com ---
compression during controlled ventilation will vent alveolar gas thru
APL valve, conserving absorbent
Circle system
--- Content provided by FirstRanker.com ---
? Circle system can be:
# closed (FGF= patient uptake, complete rebreathing after CO2
absorbed, and pop-off closed)
--- Content provided by FirstRanker.com ---
# semi-closed (some rebreathing occurs, FGF and pop-off settings atintermediate values), or
# semi-open (no rebreathing, high fresh gas flow)
--- Content provided by FirstRanker.com ---
Circle system
? Most commonly used
? Adult and child appropriate sizes
--- Content provided by FirstRanker.com ---
? Can be semi open, semi closed, or closed dependent solely on freshgas flow (FGF)
? Uses chemical neutralization of CO2
--- Content provided by FirstRanker.com ---
? Conservation of moisture and body heat? Low FGF's saves money
Circle system
Scavenging system
--- Content provided by FirstRanker.com ---
? The collection and the subsequent removal of vented gases from the
operating room
--- Content provided by FirstRanker.com ---
? Components(1) the gas-collecting assembly
(2) the transfer means
(3) the scavenging interface
(4) the gas-disposal assembly tubing
--- Content provided by FirstRanker.com ---
(5) an active or passive gas-disposal assemblyComponents of a scavenging system- APL valve, adjustable
pressure limiting valve
--- Content provided by FirstRanker.com ---
Our institute...Summary...
? The gases that are required are Oxygen, Nitrous Oxide and Air.
? The gases enter the machine at high pressures which are then
--- Content provided by FirstRanker.com ---
reduced by pressure reducing valves.
? Controller knob on each rotameter causes gas to flow and lift the
--- Content provided by FirstRanker.com ---
bobbin? The vaporizer is fitted with a dial so that the concentration of the
volatile agent can be varied
--- Content provided by FirstRanker.com ---
? The gas mixture is then delivered to the anaesthetic circuit.