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