anaesthesia machine manoj
DESCRIPTION
ANESTHESIA MACHINETRANSCRIPT
Anaesthesia machine
SPEAKER: DR. MANOJ KUMAR SHARMA
G.S.V.M. MEDICAL COLLEGE
KANPUR {U.P}
History W T G MORTON 1846 Introduced by Henry edmund gaskin
boyle in 1917…..1918 royal london American Gwathmey 1912 Geoffrey Marshal {1914- 1918} …
1919 Addition of vapourizing bottle to
flowmeter in 1920 Addition of second vapourizing
bottle and bypass control in 1926 In 1933 dry bobbin 1952 PISS, 1958 Bodock seal
Functioning
gas supply gas inlet pressure reduction
flowmeter
vapourizer
common gas outlet breathing circuit patient
FUNCTION OF ANESTHESIA MACHINE
Provide o2 Accurate mixture of anesthetics and
mixture Enable patient ventilation Minimise anesthesia related risk to
patient and staff
45-55 PSI 12-16
PSI
PNEUMATIC SYSTEM
HIGH PRESSURE
• Cylinders • Hanger Yoke
• Cylinder Pressure
Indicator(Gauge) Pressure
Regulators
INTERMEDIATEPRESSURE
Master SwitchPipeline Inlet
ConnectionsPipeline Pressure
Indicators Piping
Gas Power OutletsOxygen Pressure Failure
DevicesGas Selector Switch
Second stage Pressure RegulatorOxygen Flush
Flow Adjustment Control
LOW PRESSURE
FlowmeterUnidirectional(Check)
ValvesPressure Relief DeviceLow Pressure PipingCommon (Fresh) Gas
Outlet
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, composite{al wrapped in carbon fibre}30% more gas 70% more lighter.
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
COMPRESSED GAS CYLINDER
Body
Components of a cylinder :
Shoulder Valve
Port
Stem
Fusible material {woods metal} b/w cylinder and valve
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
COMPONENT OF CYLINDER
Valve: bronze/ brassThere 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
Pressure relief device.Pressure relief device.(safety relief device, safety (safety relief device, safety device)device)
Purpose :to vent the cylinders contents to the atmosphere if Purpose :to vent the cylinders contents to the atmosphere if the pressure of the enclosed gas increases to a dangerous the pressure of the enclosed gas increases to a dangerous level.level.
TYPES
1) Rupture Disc
2)Fusible Plug3)COMBINATIO
N OF 1 & 2
4)Pressure Relief Valve
02- 2,5N20- 3,5Cyclo-propane-
3,6Nitrogen- 1,4 CO2<7. 5%- 2,6 >7.5%- 1,6 Air - 1,5 Entonox- 7
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
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
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)
cylinder cylinder size size
DimensionsDimensions(OD*Length (OD*Length
in inchin inch))
Weight Weight (pounds(pounds) of ) of empty empty cy.cy.
OxygenOxygen N2ON2O CO2CO2 AirAir
BB 3.5 *133.5 *13 55 200L200L
19001900
psigpsig
370L370L
838838
psigpsig
DD 4.5*174.5*17 1111 400L400L
19001900940L940L
745745940L940L
838838375L375L
19001900
EE 4.25*264.25*26 1414 660L660L
190019001590L1590L
7457451590L1590L
838838625L625L
19001900
MM 7*437*43 6363 3450L3450L
220022007570L7570L
7457457570L7570L
8388382850L2850L
19001900
GG 8.5*518.5*51 9797 13800L13800L
74574512300L12300L
8388385050L5050L
19001900
HH 9.25*519.25*51 119119 6900L6900L
2200220015800L,15800L,745745
6550L6550L
22002200
ARLAS
Approx remaining in hour = (o2 cylinder in pressure in psig / 200 × o2 flow rate per minute
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.
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 yield point should not be less than 15 tons per square inch.
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.
Impact testMean energy to produce the crackshould not be less than 5 and 10 lb/ft for transverseand longitudinal strips, respectively.Bend testA ring of 25 mm width is cut from the cylinder anddivided into strips. Each strip is bent inward untilinner edges are a part, not greater than the diameterof strip
Entonox
Entonox
This is 50.50 mixtures of nitrous oxide and oxygen . The premixed contents remain in gaseous phase at pressures and temperature at which N2O by itself would normally be a liquid (pointing effect) If Entonox cylinder is stored at cold temperature (−7°C), some N2O separates as liquid and may lead to delivery of uneven mixtures, too much O2 at the beginning and too much N2O later as the cylinder empties. Danger of separation can be avoided by storing the cylinders above 0°C, immersing the cylinder in water at 52°C, inverting it thrice or keeping it above a temperature of 10°C for 2 hours before use.
Heliox
Heliox is a mixture of oxygen and helium. The latter is 86% less dense (0.179 g/L) than air (1.293 g/L).
A mixture of 21% oxygen and 79% of helium named as Heliox 21 is used to improve gaseous exchange in acute exacerbation of asthma and COPD {REYNOLD NO}
Safety system
Colour coding Label on cylinder Valve system Pin index system
Yoke assembly
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,
Bourdon’s pressure gauge
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
Pressure reducing valve
PHYSICAL PRINCIPLE
A
P
a
p
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 45‑60 PSIG and the N2O cylinders from 760 PSIG 45‑60 PSI
38
Intermediate Pressure SystemIntermediate Pressure System
Receives gasses from the regulator or the hospital pipeline at pressures of 40-55 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
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
NIST
SCHRADER
DISS
NIST
43
Second-Stage Pressure Second-Stage Pressure RegulatorRegulator
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
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
Oxygen Oxygen Supply Supply Failure AlarmFailure Alarm
THE FLOW METER ASSEMBLYThe flow meter assembly controls, measures and
indicates the rate of flow of gas passing through it
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
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
51
Flowmeter
52
Flowmeter PhysicsFlowmeter PhysicsThe rate of flow through the
flowmeter tube depends on 3 thingsPressure 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
Size of annular opening: The annular area varies while the pressure drop across the indicator remains constant for all positions in the tube.
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)
High Flow: Large annular space, therefore flow is turbulent, therefore the flow is a function of gas density .(Graham,s law)
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.
Arrangementof flowmeter
Other types of flow meter- 1.Heidbrink flow meter-contains a
tapered metal tube projected into glass tube, float is black, inverted and tapered, gives acc. Reading for low and high flow
2.Connel flow meter-it is a ball float flow meter, it is set an inclined plane and provided with two ball floats
3.Foreggar flow meter-
AUXILIARY OXYGEN AUXILIARY OXYGEN FLOWMETERFLOWMETER
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.
PROBLEMS WITH PROBLEMS WITH FLOWMETERS 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
62
Oxygen Supply Failure Oxygen Supply Failure AlarmAlarm The machine standard 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 Bowman’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
Bowman’s Whistle
OFPD datex ohmeda
OFPD DRAGER
HYPOXIA PREVENTION HYPOXIA PREVENTION SAFETY DEVICESSAFETY DEVICES
MANDATORY MINIMUM OXYGEN FLOW: Some machines require a minimum ( 50-
250ml/min) flow of O2 before other gas will flow
Some machines activate an alarm if O2 flow goes beyond a certain minimum.
MINIMUM OXYGEN RATIO: Device to protect against operator selected
delivery of a mixture of O2 & N2O having O2 conc below 21% O2 .
Hypoxia prevention safety devices:
Proportionating devices –
- link 25 in datex
ohmeda[mechanical,pneumatic
and electronic linkage]
- S-ORC in draeger,
- Mandatory minimum oxygen
flow
Mechanical linkage
LINK 25
Flow control valves are adjusted so that when 25% O2 conc is reached ,a pin on O2 sprocket engages a pin on O2 flow control knob.This causes O2& N2O flow control valves to turn together to maintain minimum O2 of 25%.
If attempt is made to increase the N2O flow beyond that ratio, the O2 flow is automatically increased.
If O2 flow is lowered too much the N2O flow is decreased proportionally
An electronic system can be used to provide a minimum ratio of O2 to N2O flow
ALARMS:
Available to alert the operator that O2-N2O flow ratio has fallen below a preset value
S- ORC
Wrong Supply Gas
Defective Pneumatics or Mechanics
Leaks Downstream
Inert Gas Administration
LIMITATION
UNIDIRECTIONAL UNIDIRECTIONAL (CHECK ) VALVE(CHECK ) VALVE
During controlled ventilation a positive pressure from breathing circuit can be transmitted back to the machine
Using O2 flush 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
PRESSURE RELIEF VALVEPRESSURE 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 bar 5 PSIG (300 cm of H2O) This valve limits the machine to provide jet ventilation
Also known as the pop-off pop-off valvevalve.
COMMON ( FRESH ) GAS COMMON ( FRESH ) GAS OUTLETOUTLET
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
BACK BARBACK 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.
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
Safety features
Antistatic tyre Pressure reducing valve 02 failure alarm 02,N20 lock Florescent back panel of
rotameter 02 flush
Essential Features Purpose
Noninterchangeable gas-specific connections to pipeline inlets (DISS)1 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
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 (eg, oxygen concentration)
Prevent use of the machine without essential monitors
Vaporizer interlock device Prevent simultaneous administration
of more than one volatile agent
Capnography and anesthetic gas measurement
Guide ventilation; prevent anesthetic
overdose; help reduce awareness
Oxygen flush mechanism that does not pass through vaporizers
Rapidly refill or flush the breathing circuit
Breathing circuit pressure monitor and alarm
Prevent pulmonary barotrauma and detect sustained positive, high peak, and negative airway pressures
Exhaled volume monitor Assess ventilation and prevent hypo- or hyperventilation
Pulse oximetry, blood pressure, and ECG monitoring
Provide minimal standard monitoring
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
THANKS