Vaporizers 2015 spmc

VAPORIZERS

Dr. deepak kumar Resident in Anaesthesia deptt

S.P.Medical College & A.G.Hospitals, Bikaner

What is a Vaporizer?

A VAPORIZER IS AN INSTRUMENT DESIGNED TO FACILITATE THE CHANGE OF A LIQUID ANAESTHETIC AGENT INTO A VAPOR

AND ADD A CONTROLLED AMOUNT OF THIS VAPOR TO THE

FGF.

Function of Vaporizers

• Produce vaporisation of volatile agent• Mix vapour with fresh gas flow• Control the mixture despite variables

►To deliver safe and accurate concentration of inhalational agents to the patient.

Applied Physics

• Factors affecting vaporization of a liquid

1.Temperature

2.Volatility

3.Surface area

4.Removal of vapor from the vicinity of the liquid.

Applied Physics • Vapor• Gas • Critical temperature• Vapor pressure• Boiling point• Partial pressure • Heat of vaporization• Specific heat• Thermal conductivity• Thermal capacity

Vapor

• Vapor is the gaseous phase of a substance which is normally a liquid at room temp. and atm. pressure

Gas

• Gas is a substance which exists only in the gaseous state at room temp. and atm.

Critical temperature

• It is the temperature, above which no amount of pressure will convert a gas to a liquid.

02=-118.4°C; N2O= 36.5°C; CO2= 31°C.

• The pressure required to liquefy a gas at its critical temp. is the CRITICAL PRESSURE .

Vapor pressure

• When enclosed in a container molecules of a volatile liquid break away to form vapor.

• Vapor pressure is the pressure with which they bombard the walls of the container.

• Vapor pressure depends only on temp and nature of liquid.

• Vapor pressure of an agent determines how much of vapour will be formed from 1 ml of the liquid.

• Since diff anaesthetic agents have diff vapour pressure so need separate vaporizers.

Boiling point

• Boiling point of a liquid is that temp at which the vapor pressure is equal to the atmospheric pressure.

• Lower the atmospheric pressure, lower the boiling point.

Partial pressure

• The part of total pressure due to any one gas in the mixture

• Depends on – Nature of liquid and Temp.• Clinical significance-

Patient uptake and anaesthetic depth are directly related to partial pressure.

• HEAT OF VAPORIZATION-

It is the number of calories needed to convert 1gm or 1ml of liquid to vapor.

• SPECIFIC HEAT-

Quantity of heat required to raise the temp of 1gm or 1ml of substance by 1*c .

• THERMAL CONDUCTIVITY-

A measure of speed with which heat flow through a substance .

• THERMAL CAPACITY-

Amount of heat stored in vaporizer body

= specific heat x Mass

CLINICAL SIGNIFICANCE-• liquid with low specific heat vaporize easier.• Higher the thermal conductivity, better a

substance conduct heat• Vaporizers construct of material with high

thermal conductivity and specific heat e.g.- copper, bronze to minimise temp changes when in use.

Related physics

THERMOSTABILISATION Methods :-

Vaporizer constructed of metal with high thermal conductivity.

Heavy metal parts act as heat reservoir. Wicks to be in contact with the metal part so that

heat loss due to vaporization is quickly replaced. Immerse vaporizer chamber in a large mass of water.

Related physicsTHERMOCOMPENSATION-• Some means to maintain the vaporizer

output constant despite any temp changes

Methods -

1.Alteration in splitting ratio(automatic compensation) e.g.- bimetallic strip in Tec vaporizers, ether filled bellows in penlon vaporizers, EMO(Epstein Macintosh Oxford)

Related physics

2.Computer control-electronic vaporizers.

3.Manually adjust flow- measured flow , drager vapor.

4.Supplied heat- Tec 6(electrically heated).

Properties Of Common Anaesthetic Agents

Agent Boiling Point at 100 kPa(degree Celsius)

Vapor Pressure(at 20 deg C)

MAC value(vol% ) in 100% O2

1) Ether 34.5 440 19

2) Halothane 50.2 243 0.75

3) Enflurane 56.5 175 1.68

4) Isoflurane 48.5 238 1.15

5) Desflurane 22.8 669 6.4

6) Sevoflurane 58.6 157 2.0

7) Trilene 87.5 57 0.17

Terminology for vaporizers

PLENUM- FGF is pushed in to the vaporizer(high resistance).

DRAWOVER- Gas is pulled in to the vaporizer by the patients own inspiratory effort(low resistance) e.g.- Goldman,EMO,OMV

INHALER- A drawover vaporizer in which the carrier is air.

SPLITTING RATIO• The ratio of the bypass gas to the gas going to

the vaporizing chamber is called the splitting ratio

• It depends on-

1.The resistance of the two pathways, which inturn depends on the variable orifice of the inlet/outlet.

2.Temp of the liquid/carrier gas

3. Flow rate of gases.

CLASSIFICATION

• Dorsch & Dorsch classification (1979)

1) Regulation of output concentration

2) Method of vaporization

3) Location of the vaporizer

4) Temperature compensation

5) Specific anaesthetic agent

CLASSIFICATION

• Dorsch & Dorsch classification


a) Variable Bypass type

b) Measured flow type





Flowmeter

Patient

VARIABLE BYPASS

Flowmeter

Patient

Flowmeter

Patient

MEASURED FLOW VAPORIZER

• Uses a measured flow of carrier gas to pick up agent

• Consist of-

1.Vaporizer

2.flowmeter assembly

3.Vaporizer circuit control valve

Cont...

• Operator has to set the flow to the vaporizer and bypass with separate flowmeters

• This means that respective flows have to be calculated for a given temp and vapour output.

Measured Flow Vaporizer

V V

C

L

CLASSIFICATION




a) Flow over

b) Bubble through




Flow over

• A stream of gas passes over liquid surface • Efficiency depend on-

1. Gas-liquid interface e.g.- baffles, spiral tracks, wicks.

2. Velocity of carrier gas flow

3. Height of gas

Bubble through

• Bubble the gas through the liquid • efficiency depends on-

1. size of bubbles

2. depth of the liquid

3. velocity of carrier gas

E.g.- sintered diffuser

-cowl in Boyle’s bottle

BUBBLE THROUGH VAPORIZER

CLASSIFICATION





a) VOC(Vaporizer outside the circuit)

b) VIC (vaporizer inside the circuit)



In system vaporizer(VIC)

• Should have standard male and female 22 mm fittings or standard screw threaded fittings,inlet and outlet ports should have arrows.

• Should have low resistence.• Vaporiser concentration and output vary• Easy to wash and clean• Drawover vaporizers eg- goldman,EMO,OMV

OUT OF SYSTEM VAPORIZERS(VOC)

• Usually on back bar – b/w flowmeter and FGF outlet

• Most variable bypass vaporizers and all measured flow vaporizers are VOC type.

CLASSIFICATION






a) Non compensated

b) Compensated


EFFECTS OF TEMPERATURE

GIVING HEAT

TEMP COMPENSATION

• To maintain a constant output from the vaporizer,mechanisms to compensate for the fluctuations in temp are to be employed.

• Method –

1. automatic- alteration in the splitting ratio(bimetallic strip in tec vaporizer,ether filled bellows in penlon vaporizers,EMO

2.Supplied heat- tec 6(electrically heated)

3.Computer control- electronic vaporizers

TEMPERATURE COMPENSATED


BIMETALLIC STRIP

BIMETALLIC STRIP


CLASSIFICATION







a) Agent specific

b) Multiple agent

CLASSIFICATION

• Gray & Nunn Classification (1971)

1) Plenum vaporizers

2) Draw over vaporizers

3) Vaporizers for use inside a circle anaesthetic system

CLASSIFICATION

• Gray & Nunn Classification

1) Plenum vaporizers

Fresh gas flow is forced into a chamber

Unidirectional gas flow

Relatively high resistance to gas flow

e.g. Boyle vaporizer, copper kettle,

Tec series vaporizers

CLASSIFICATION


2) Draw over vaporizers/ Inhalers: Air or anaesthetic gases drawn over or through the vaporizer either by pt’s own respiratory efforts or by a self inflating bag or manual bellows.

Very low resistance to gas flowe.g. EMO vaporizer, Oxford

miniature inhaler, emotril, tecota vaporizers.

CLASSIFICATION


3) Vaporizers for use inside a circle anaesthetic system

e.g.- Goldman vaporizer

Rawbotham vaporizer

NEWER CLASSIFICATION.

METHOD OF REGULATING OUTPUT CONCENTRATION(1) Conc. Calibrated(2) Measured flow

METHOD OF VAPORISATION(1) Flow over(2) Bubble through(3) Injection

TEMP. COMPENSATION(1)Thermocompensation(2) Supplied heat

Factors affecting vaporizer performance

• Flow rate• Temperature• Barometric pressure• Intermittent back pressure• Gas direction• Liquid levels• Anaesthetic agents

• Carrier gas composition (N2O causes transient drop)


• Flow rate At high flows,the vaporizer delivers less

anaesthetic concentration than is set on the dial

problem is solved by increase the surface area of contact b/w the fresh gas and anesthetic agent

Eg- WICKS

TEMPRATURE• As anaesthetic molecule escape temp

decreases more difficult for the remaining molecules to escape less vaporisation.

• Thus at lower temp there is less vaporization.

• Problem solving- Giving heat Giving flow

Giving heat

1.Vaporizer material

good conductor(high thermal conductivity)

act as a heat reservoir(high specific heat)

2.Supplied heat (tec-6 electrically heated)

Giving flow

• Giving flow (thermocompensation) by alteration in splitting ratio

1. Mechanically

2. Compuer controlled


• Intermittent back pressurePumping effect(hill and lowe effect)Pressurizing effect(cole effect)

Pumping effect(Hill and lowe effect)

• The effect of changing pressure during IPPV increasing the output of the vaporizer is called the “pumping effect”

• During positive pressure ventilation, pressure transmitted back results in compression of gas.

• Since the vaporizing chamber volume is much larger than the ‘by pass’ channel volume, more fresh gas gets compressed in to it.

Cont…

• This extra fresh gas that enters the vaporizing chamber collects anesthetic vapour

• Some of the rapidly expanding gas (containing vapour) enter the inlet of the vaporizer and cross over into the ‘bypass’ channel.

• The addition of the ‘bypass’ vapour to the vaporising chamber raises the final concentration of anesthetic delivered.

Pumping Effect

Pumping Effect

Pumping Effect

Pumping Effect

Pumping Effect

Pumping Effect

Modifications to reduce the ‘pumping effect’

• By pass channel made larger• Inlet tube made longer• Exclude wicks from inlet• Increased resistance – a high internal

resistance to “resist” changes to flow.• Check valve at outlet of the vaporizer -Fluotec

2 • Check valve upstream to junction with the

oxygen flush.• Pressure relief valve.

Large bypass channel

Long inlet tube

Increased resistance

One way valve (open)

One way valve (closed)

Pressurising effect

• k/a ‘cole effect’ – decreased output of anesthetic agent.

• An inreased in pressure causes an increased pressure inside the vaporizer.The carrier gas is compressed but the vapour pressure of the volatile anesthetic is unaffected.Net result decreased conentration of anesthetic delivered.

Pressurizing Effect

Carrier gas composition

• Most vaporisers are calibrated using 100% o2• Composition of carrier gas affects output in

many(vaporiser aberrance)• If add N2O- decreased output(25% less with

100% N2O)due to solubility of N2O in agent .As N2O dissolves in liquid anaesthetic.Flow of gases exiting vaporiser decreases.

• Once saturated with N2O output gradually increases but is less than before(10% less with 100% N2O.

EFFECT OF BAROMETRIC PRESSURE

• Vaporizers are calibrated at std. atmospheric pressure(at sea level)

• Low boiling point,high SVP anaesthetic volatile agents- more susceptible to influence by barometric pressure.

• Vapour pressure of agent is independent of barometric pressure.

• Effect of low atm. Pressure- deliver HIGHER concentration if measured in volume% but deliver same partial pressure

Cont….

• Clinically effect unchanged

• Effect of high atm.pressure-

increased density of gas increased resistance through vapourising chamber decreased vapour output both in partial pressure and volume%

SPECIFIC VAPORIZERS

Early methods• OPEN DROP METHOD:-

Inhalational anaesthesia by vaporization of a liquid anaesthetic placed drop by drop on a gauze/ mask covering the mouth and nose.

Devices- Schimmelbusch mask

other modification- Yankauers, Bellamy gardner

CONT..

• SEMI OPEN-

a frame added to “keep the ether in” in an enclosed area- permitted some degree of rebreathing.

e.g.- Ogston’s inhaler

Flagg’s can

Early devices- open drop method(schimmelbusch mask,

yankaeur mask and bellamy gardner wire mask)

Semi open drop method

Ogston mask with schimmelbusch frame

MORTONS ETHER INHALER

OPEN ETHER ADMINISTRATION

• TECHNIQUE- Volatile anaesthetic dripped on to a gauze:1. ETHER- 16 layers gauze over mask2. CHLOROFORM/ETHYL CHLORIDE- 12 layers of gauze/1

layer lint(chloroform dropped over half the area)- gradually increased no. Of drops/min- During inspiration air passed through the gauze and

vaporizes the liquid anaesthetic into high concentration.

Open drop ether

• Bellamy gardner dropper

- amber coloured

- control on pouring

- capacity – 90 ml ether

INDUCTION• WITH ETHER • RATE OF DROPS 1ST min = 12 drops = 1 % 2nd min = 25 drops = 3 % 3rd min = 50 drops = 6 % 4th min = 100 drops = 10-12 %

• ETHYL CHLORIDE - 3 to 5 ml - 3 to 5 %• Rate of drops 1st min = 30 drops 2nd min = 60 drops 3rd min = 90 drops

MAINTENANCE• Conc.for maint. with ether is 6 -8 %• Heat loss = 200-300 cal/min• Temp. above and below mask = 2-3 degrees <

room temp.• Temp. at mask = 0 – 1 degrees C

• Gas comp.under mask 0% ether = 80% N2 + 20% O2 5% ether = 76% N2 + 18% O2 10% ether = 72% N2 + 16% O2

Advantage of open drop

• Easy to administer• Low dead space 40-60 ml• Low resistence• Wide margin of safety • Relatively cheap

Disadvantage of open drop• Significant rebreathing• Hypoxic mixtures may occur• Poor control of inspired gas concentration• Inability to assist or control ventilation• No conservation of heat or humidity• Difficult airway management especially during

head and neck procedure• Pollution of the operating room• Hazardous especially with flammable agents.• Skin burn.• Eye injury

In system vaporizers(VIC)

• There are two ways that gas flows through a vaporizer

- push through

-Drawover

Drawover anaesthesia

• Drawover system :

- provide anaesthesia without a supply of compressed gases.

-Atmospheric air – main carrier gas

-drawn by the patient’s inspiratory efforts

- volatile agent (ether or halothane) added to vaporizer

- Inhaled by the patient via a non-rebreathing valve.

Drawover anaesthesia

• The component of a drawover circuit

EMO Vaporizer Epstein, Macintosh, Oxford (EMO) introduced

in 1952 Classification-• Variable bypass/conc. calibrated• Flow over with wicks • Temperature compensated by supplied heat and

altered flow. • Agent specific-used for ether, halothane, chloroform

and trilene.• Can be a part of a drawover system or used as a

plenum vaporizer• Low resistance(<1.25cm water at 40 Lpm flow)

EMO VAPORIZER

• Wt- 6.5 kg ; ht 24cm ;dia 23cm

• TRANSIT position- seals ether chamber

• CONTROL lever-upto 20%

• INLET/OUTLET – R to L

• TAP for filling /draining water chamber at bottom

• Outlet(male) inlet(female)

• 1250ml water filled in water chamber

A- Inlet B- Outlet C- Water compartment D- Ether E- Vaporizing chamber F- Thermo compensating

valve G- Off/on valve H- Mixing chamber I- Water drain

Ctd• FILLER-depress to fill (control lever at 0-not

transit- for air to escape) springs back automatically.

• LEVEL INDICATOR- moves only after 150 ml ; add 300ml for full (fill with control at 0 –not at ‘in transit’.

• TEMP.INDICATOR-rod with black & red bands and metal top

20-25 degrees-black line with metal top >32 degrees – red band- temp above

working range

EMO(ctd)• Thermocompensation mechanism at outlet of

v.c.– metal bellows with liquid Ether[ether capsule] &

connected to plunger– temp. range; 15-29 degree Celsius

• Water jacket serves as heat reservoirChecks(1) check level indicator-> put “in transit”-> invert –

indicator should fall to full.(2) close outlet- connect OIB to inlet-> put “in transit”->

press bellows-> open filler –no air should escape.(3) release filler-set at 10% -rpt above(4) attach bellows to outlet->block inlet –> set at 2 %

-suck air –> should hear a hissing if safety release valve is working

EMO(ctd)• Care-Mark I--empty Al water jacket every 3 months, Mark II &

III- yearly water check EVALUATION 1. Calibration of EMO is accurate only for intermittent gas

flows; maintains output at 5-13L/min flows. Highest conc. delivered 16%. If use as plenum i.e. blow air into it –increase output

2. Climate; Cool-add antifreeze (2% glycol) Warm- cool by allowing agent to vaporise -refrigerate -air will deposit water in cooler vc 3. Splashing during transit if in ON position. 4. Sticking of rotor-PTFE coating in Mk4 (Stetson) 5. Advantage- compact, low cost, portable, useful in mass

casualties, no effect of altitude, easy maintenance, no need for sterilisation

OXFORD INFLATING BELLOWS

• Self inflating bellows used with spontaneous/controlled ventillation

• Bellows sit vertically,internal volume maintained by a spring; 6 bellows- 150 ml each

• 2 unidirectional flap valves• Magnet to inactivate distal unidirectional

valve.

Oxford inflating bellows

Spontaneous ventilation

Assisted ventilation

Assisted ventilation

Oxford miniature vaporizer(OMV)

Introduced by Epstein, Macintosh and Mendelssohn in 1941.

• Conc. Calibrated• Draw over vaporizer (low resistance)• Flow over with wicks• Temperature regulated by means of calcium

chloride( supplied heat)• Outside the circuit, can be used as plenum

vaporizer

OXFORD MINIATURE VAPORISER(OMV)

• Simple portable inhaler• for less volatile agents – halo, trilene, chloroform• Fairly accurate over a short period of time• 13.5 cm high,1060 gms with full water jacket.• Control lever, alternative scales for halo(0-4%),tri(0-1.5%),

methoxy (0-0.6%)• water jacket at base with 25% glycol• Body stainless steel/wicks of stainless steel gauze• Plugged into outlet of EMO-performance unaffected by IPPV- can

place on pt side of bellows• Highest conc delivered 3.5% hal

OMV (ctd)

• Special filler with 2 springs

light pressure-air relief

more pressure-opens filler • Funnel around filler has capacity of 10ml, covers 1/8th of level

indicator. A second 10ml can be added• cleaning-drain by tipping after pressing filler lever, wash out

with alcohol or Ether.• If used with EMO flow is R to L • Another version for use with continuous flow machine

then flow is L to R• direction of gas flow marked with an arrow

Disadvantage of OMV-only 20 ml ; cannot mount on backbar

Goldman Vaporizer

• Classification

- concentration calibrated

- flow over without wick

- no temp compensation

- multiple agents – halothane,trilene

- in or out of system

Goldman vaporizer

• Small glass bowl• Capacity 20 ml• Bowl attached to a head, which divide gas b/w

bypass and vaporizing chamber• Control lever at top; max conc. Delivered at 3rd

mark of 2.21%• Young modification- added a wick(increase to

4%)• Halls modification – 2 in series

GOLDMAN VAPORIZER

MARK I MARK II MARK III

1. Self locks Click stops No lockingin off position in each setting

2. DIVISIONS Off-1-2-3-ON Off-1-2- ONOff -1-2-3-ON

3. Max conc Max conc Max concdelivered at delivered at delivered at3 position. 3 position. On.

ROWBOTHAM VAPORISER

• Has a wire gauze wick

• 2marks to fill till

• Top mark and blue mark

• Max. at full on 3.10%

ADVANTAGES

• Portable• Easy to operate• Low resistance-used as VIC• Calibrated at high flows of 30 Lpm so safely

use with O2 flush• Small, inexpensive• Safe- cannot deliver high conc.’s

DISADVANTAGES• No temperature compensation- Level of

halothane kept at full mark• Tilting - pouring of liquid in respiratory

tract• Back pressure or pumping effect• Small capacity vaporising chamber - so

delivers low halothane concentration.• agitation/splashing -5%

Boyle’s bottle vaporizer

• Classification• 1.Variable bypass• 2.Flow over or bubble through• 3.Not temperature

compensated• 4. Agent specific

(ether,halothane,trilene)• 5.Outside the circuit

Boyle’s bottle

Boyle Bottles• Ether Bottle • Larger vc-300 ml filled fully• U tube & hood of Cu• Has 4 lines between off & on-begins to operate

at 2nd mk• Trilene bottle -100ml for ½ inch liquid depth• Chrome plated U tube& hood; cowl adjusted by

stainless steel plunger• Delivers 0.5-2 %

Boyle Bottles

• Halothane bottle• Uses only control tap –no plunger/hood• Control lever marked 1-10 (8%)

starts at 3 , at 4 about 1%• Inlet tube plugged at end; hole on side 1

cm above

BOYLES BOTTLE• FACTORS AFFECTING OUTPUT

1. Temp. of liquid

2. Plunger level

3. Control lever position

4. Level of liquid

5. Eccentricity of hood

6. Agitation of vaporiser as during pouring of liquid in bottle(>5%x 15 secs)

BOYLES BOTTLECARE & CLEANING• Empty after use/allow to dry• special grease for free rotation of drum• Plunger loose- tighten the gland nut• replace packing in gland nut- cotton, neoprene,

nylon• bottle may chip off leading to leakage• bottle washer may get damaged• pressure build up in unused ether bottle• static charges on cork-chain

Copper Kettle vaporizer Described by Lucein Morris in 1952.

Classification-

• Measured flow

• Bubble through

• Temperature compensated by supplied heat and manual flow alteration.

• Multiple agent ( chloroform, ether,halothane)

• Outside the circuit

• 2 models 160ml/400ml

Copper kettle vaporizer

• Constructed of copper

-High heat capacity

- high thermal conductivity

-High degree of accuracy

Copper kettle vaporizer

• A- Filling funnel• B- Drain• C- Inlet • D- Sintered bronze

porex disc• E- Outlet

Obstetric inhalers• Emotril• Cyprane

• Provide TV 250-1000 ml • work over RR’s of 12-30/min• resistance of breathing to be

<1.25 cm H2O at 30 LPM.

TEC VAPORIZERS

• CLASSIFICATION (TEC 1 to 5)1.Variable bypass2.Flow over with wick3.Out of system4.Temp. Compensated by automatic flow

alteration5.Conc. Calibrated6.Agent specific

TEC 2

• Used only for Halothane & methoxyflurane• Capacity 150 ml• Calibrated upto 4% (in increments of 0.5% )•Temp. compensation by bimetallic strip• Filling tap at side, draining at bottom •Level indicator on side•Conc. Dial in front, attached with a spindle

TEC 2• Not accurate below 4L/min

• <2L/min flow and <2% dial setting->delivers less

• >2% dial setting -> deliver more

• With N2O it gives greater output at lower setting and less output at higher setting

• Prone to pressure changes:

pumping effect at low flows

pressurizing effect at high flows .

• Care and cleaning

Drain halothane every 2 week and discard as THYMOL accumulates sticking of spindle and bimetallic strip.

HAZARDS-

1. Tipping

2. Agitation high output

3. Reverse flow:->back pressure changes

4. Sticking of control dial due to thymol

5. Between off and 0.5% some output can occur varying with FGF.

6. Small leak in off position.

TEC 3

Construction:-1.Conc. Control dial is on top

2.Calibrated from off to 5% in 0.5% gradations

3.Locking lever to be depressed before dial can be turned

4.Screw cap filler with drain at bottom

5.Optional pin safety system for filling

6.Sight window for liquid level on left

TEC 3

•Used for Halothane, enflurane, isoflurane & sevoflurane

•Capacity : 135ml (with dry wicks)

100ml ( with wet wicks)

•A bimetallic strip increases flow through the bypass chamber when temperature increases.

•Negligible back pressure changes

•No non return valve

•Less affected by fresh gas flow and composition of carrier gas

•Control knob less likely to stick

Cont...Internal structure:• Completely redesigned• Has 2 sections- lower vaporizing chamber and upper

duct and valve system• 2 bypass channels- one direct gas stream over

bimetallic strip• Bimetallic strip at inlet of 2nd bypass• Gas exits VC by way of the control channel and joins

gas coming from the bypass• Bypass is located concentrically within the vaporizing

chamber.

TEC 3• Accur. falls off at high

flow rates & dial settings

• All are accurate with low dial settings

TEC 3EVALUATION • Sudden increase or decrease in carrier gas flow,

intermittent back pressure and upstream O2 flush has negligible effect on vapor output.

• N2O has got little effect on output• Performance in 0-0.5 % range governed mainly

by conc. dial & less by FGF.• Upto 90° tipping has no effect

HAZARDS: • FAULTY LOCKING LEVER.

• TIPPING TO 180 DEGREE INCREASES CONCENTRATION DELIVERED TO > 12%.

• LEAKS SMALL AMOUNT OF VAPOUR IN OFF POSITION.

• REVERSE FLOW INCREASES OUTPUT.

TEC 4Used for halothane, enflurane and isoflurane Entire new look-> Select-a-Tec manifoldCapacity 135ml (with dry wicks)

100 ml ( with wet wicks)Graduation from 0-5% ( in 0.25% increments from 0 -1%, and 0.5% increments thereafter)Depress release button on left of control dial to turn on the vaporizerLocking lever on rear- Vaporizer can be turned on only if locked on manifold.Two filling mechanism

1. screw cap with drain plug

2.keyed filling device

Improvement over tec 3• Output unaffected by back pressure changes under

clinical conditions• Unaffected by tipping even upto 180°

Limitations-

1. Excess pressure(>400 mmHg) cause decrease in output.

2.Not so accurate at low flow rates, low dial settings and larger pressure fluctuations.

3.Overfilling possible.

4.Use of N2O decreases output.

5. Difficulty in operation one handed.

TEC 4

TEC 5Used for Halothane, isoflurane , enflurane & sevofluraneCapacity 300ml ( with dry wicks)

225ml (with wet wicks)Graduation 0-5% ( 0.2% increments from 0-1% and 0.5% increments thereafter)

Features-

1.Top control dial

2.Locking lever

3. Release button at rear of dial

4.Sight glass – bottom right

5.Keyed filling device:-FILLING DRAINING PORT

-LOCKING LEVER TO SECURE FILLER BLOCK

-SMALL LEVER AT BASE ALOWS LIQUID TO BE ADDED OR DRAINED

Tec 5Features :• Internal baffle system• VC lies within the

bypass, which lies along side of the vaporizer.

• Bimetallic strip at the base in bypass.

• Before reaching VC –helical IPPV assembly--spiral wick.

TEC 5• Introduced in 1989 responding to criticism of the Tec 4.

Improved features of TEC 5:-

1. Bypass chamber at the base; an improved bimetallic strip.

2. Improved safety interlock.

3. Agent capacity increased from 125 ml to 300 ml.

4. Helical IPPV assembly to minimize effects of PPV.

5. One handed dial control and more obvious “off” position.

6. Service interval now three years.

7. Improved characteristics with tubular woven cotton wicks

8. Accurate with gas flow 5Lpm, dial settings < 3 %.

9. Greatest accuracy between 15-35 degree celcius

Hazards of TEC 5

• More prone to pumping effect then Tec 4.• Large liquid loss if filling port is opened.• Overfilling – bottle adaptor loose, vaporizer

on• Reverse flow increases output.• Carrier gas composition affects output.

TEC 6• Classification –1.Conc. Calibrated

2.Injection vaporizer

3.Thermocompensated by supplied heat or electrically heated.

4.Electromechanically controlled dual circuit.

5.Gas-vapour blender.

6.pressurized

7.Single agent – Desflurane

• Used only for desflurane.• Capacity 390ml • Graduation 1-18% ( 1% increments from 1-

10 and 2% increments thereafter)• Maximum permissible flow 20L/min• Since VC is sealed from atm. special filler

system is required.• Various LEDs in front pannel:-

Amber : without alarm- warm up

Amber : with alarm- agent level below 50 ml

Green : operational

Red :no output due to:--1. Low agent level <20ml

2. Power failure

3. Malfunction

4. Tilted vaporizer beyond 20 degree

TEC 6•Desflurane heated to 39 deg celcius in a sealed chamber, adjusted by H.•VP 1300mmHg in sump.•Carrier gas flow restricted by O, so that pressure is ~ to flow.•Pressure sensed by P , which readjusts R1 so that desflurane flow is ~ to FGF. •Control dial adjusts R2, and thus the output conc.

• H-heater• O-fixed orifice• P-differential pressure

transducer• R1-adjusted by P• R2-adjusted by control

dial

EVALUATION:-• Output almost linear at 3%,5%, 7%.• Slightly low output at <5l/min• Ideal temp 18-30 deg celcius• Tilting resistant • Pumping effect insignificant• Carrier gas effect minimal.

TEC 7•Similar to TEC 5

•Used for isoflurane, enflurane , sevoflurane

•Capacity 300ml (with dry wicks)

225ml (with wet wicks)

•Graduation 0-5% ( 0.2% increments from 0-1 and 0.5% increments thereafter)

•Available with 3 filling devices– funnel filler, Quikfil, Easyfil.

•New ergonomics and design.

•Soldered sump assembly eliminating seals

•Improved sight glass design

•Clear agent color identification

Tec 7

Characteristics of Drager Vaporizers

MOST ACCURATE

CLASSIFICATION-• Conc. calibrated• Flow over• Temperature compensated• Agent specific• Out of circuit

Drager vapourizers

Drager Vapor 19.1

Used for Halothane, isoflurane, enflurane and sevoflurane

Capacity 200ml

Calibrated from 0-5% (o.2% increments in between 0-1 and 1% thereafter)

DRAGER VAPOUR 2000

Penlon sigma delta vaporizer

• Specifications-• wt :5 kg approx• Capacity volume : at MAX mark 250 ml• Flow range: operating flow range .2 to 15 lt/min

SAFETY FEATURE-

1. Keyed filler

2. low filling port

3. Interlocks

4. Secured vaporizers

Cont..

ALADIN CASSETTE VAPORIZER

Classification-1.Conc. Calibrated

2.Flow over

3.Automatic thermocompensation

4. Agent specific

Features-

1.Cassettes containing liquid anaesthetic inserted into a port

2.Agent recognized and dispensed into the stream of FGF

3.Tipping resistant and maintenance free

4.Power battery backup and adequate O2 pressure mandatory

5.Fixed output irrespective of fresh gas mixture

6.Extremely light and can be removed with one hand.

.

Use with datex-Engstrom AS/3 ADU

SIEMENSClassification• Conc calibrated

• Injection

• No thermocompensation

• A caliberated throttlevalve is opened and closed by user and thus regulate the pressure exerted by FGF on surface of liquid anaesthetic agent

• This pressure tends to force liquid to atomize at the injector nozzle

• The liquid droplets vaporize in the flowing FGF.

Agent specific filling system

• A vaporizer designed for a single agent be fitted with a permanently attached agent specific device to prevent accidental filling with wrong agent.

• Reduce air pollution

TYPES-

1.Keyed filling system

2.Screw capped filling system

3.Pin safety system

TEC 4 (KEY FILLER)

TEC 4 (KEY FILLER)

TEC 4 (FUNNEL FILLER)

TEC 4 (FUNNEL FILLER)

KEY FILLERS

KEY FILLER

KEY FILLER

Easy filling system

Quick fill system

Vaporizer mounting systemIf >1 vaporizer can be switched on at a time:-• The patient exposed to a overdose of

anaesthetic agent• The downstream vaporizer is contaminated.

TYPES-

1.Select a tec back bar- a switch on the back bar may be used to direct gas flow through only one vaporizer at a time.

2.A mechanical locking system

3.A mechanical interconnector

Selectatec system• Pair of port valves for

each vaporizer• Vaporizer is mounted

and locked on back bar• When ON 2 plungers

open the valve ports & activate extension rods that prevent other vaporizer.

Vaporizer Mounting Systems

• Only one vaporizer can be turned on

• Gas enters only the “on” vaporizer

• Leak of trace gas is minimized.

BACK BAR DEVICES

• Ohmeda selectatec –has pins in manifold linked to control dial

• If one on –extend to prevent other

DRAGER LOCK

• For Drager 19.2 has rotating bar on manifold with teeth that fit into a cut out on the control dial

Order of Vap. Less potent – upstream More potent – downstream If equipotent: low VP – upstream High VP – downstream

ALSO , If explosive – downstream Trilene – downstream Easy to clean - downstream

ORDER OF VAPORISERS

UP STREAM DOWN STREAM

SEVOFLURANE ENFLURANE ISOFLURANE HALOTHANE DESFLURANE

VP-157 175 238 243 669

Hazards of contemporary vaporizers

Incorrect agent/ Misfilling

Tipping

Overfilling

Reversed flow

Simultaneous inhaled agent administration

Leaks

Electronic failure

IDEAL VAPORIZER

• Deliver fixed desired conc. • Independent of-

temp

flow rate

carrier gas alteration• No effect of back pressure• easy to maintain and clean• Agent specific

Health & Medicine

Vaporizers 2015 spmc