Principles of vaporizers and older vaporizers - PowerPoint Presentation

Slide1

Principles of vaporizers and older vaporizers

Presented by: Dr

Rashmi

Moderator: Dr

Kartik

SyalSlide2

The start

1847:

John Snow (1813-1858)

described the relationship between temperature and the saturation of ether vapor

first major milestone in the attempt to control the strength of anesthetic vapor administered to patients

1952:

Dr. Lucien E. Morris (1914-2011)

Copper Kettle vaporizer

first system to permit very fine control over the concentration of volatile anestheticsSlide3

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 gas flow to the patient.

known

and reproducible concentration of anaesthetic vapour delivered in a safe and reliable mannerA vapour is the gaseous phase of an agent which is normally a liquid at room temperature and atmospheric pressure.

INTRODUCTIONSlide4

May be expressed as

VOLUME %

:- it’s the concentration of gas in a mixture. / no of units of volume of gas in 100 units of

vol

of total gas mixturePARTIAL PRESSURE :- In a mixture of gases the pressure exerted by each gas is the same as that which it would exert if it alone occupied the container Concentration of vapourSlide5

Method of regulating output concentration

1. Concentration calibrated (variable-bypass)- direct type

2. Measured flow - indirect type Method of vaporization 1. Flow over 2. Bubble Through 3. Injection classificationSlide6

Temperature compensation

1. Thermo-compensation

2. Supplied heat

Specificity Agent specific Multiple agent

Resistance

1. Plenum

2. draw over

VIC / VOC

Classification contd.Slide7

Basic designSlide8

Total flow

from

the

machine split

by a variable resistance proportionating valveOne part (usually major): through bypass chamber &Other (

usually small

): through

vaporizing

chamber

agent concentration controlled by dial calibrated in volumes percent

Concentration caliberatedSlide9

Dial with high concentrationSlide10

Dial with low concentrationSlide11

ratio

of the bypass gas

to

gas going to the vaporizing

chamberdepends on:Resistance

of

the two pathways,

depends on the variable orifice of the inlet/outlet.

Temperature

of the liquid/carrier gas.

Flow rate

of gases

Splitting ratioSlide12

separate

, independent stream of

vapour

carrying

gas, added to the fresh flowTo calculate the vaporizer output, to know Vapor pressure of the agentThe atmospheric pressure

The total flow of gases

The flow of the vaporizer

Eg

:

Ohmeda

Tec 6, sp for Desflurane, copper kettle

MEASURED FLOW VAPORIZERSSlide13

Method of vaporization

:

Flow

over Vaporizers : carrier gas flows over the liquid

agent, saturated with vapor.Bubble through Vaporizers : carrier gas is bubbled through the liquid agent Injection Vaporizers :

known

amount of liquid agent or pure vapor

injected

into the gas stream to provide the desired concentration.

Classification

contdSlide14

Flow overSlide15

Bubble throughSlide16

TEMPERATURE COMPENSATION

maintain

a constant output

compensation for fluctuations

in temperature Cooling affects vapour concentration.Mech: Alteration

in the splitting ratio (automatic

compensation)

Eg

.

Bimettalic strip in tec

vaporizer

Supplied

heat –

tec

6 (electrically heated)

copper metal

Ether filled copper bellows ex

Penlon

vaporisers

TEMPERATURE UNCOMPENSATED:

boyle’s

bottle,

goldman

etc

TEMPERATURE BUFFERING

hot water jacket/ heat sink (ex OMV)

Classification

contdSlide17

On cooling,

bimetallic

strip

bends,moves

awayreduces the resistance to flow=more flow into vaporizing chamberAutomatic compensationSlide18

SPECIFIC AGENT

use

with

one specific agent.Must be labeled Use of other agents may give incorrect concentration, may damage vaporizer, harmful byproducts. MULTIPLE AGENT

:-

Rarely in

use, not

advised.

Ex OMV, EMO, Copper kettle

Classification contd.Slide19

VOC = Vaporizer-out-of-system

localized

btwn

flowmeter and CGO Oxygen from the flowmeter enters the vaporizer prior to entering the breathing circuit.VIC = Vaporizer-in-systemOxygen enters the breathing circuit from the flowmeter

either in circle , at CGO, inhalers

i.e

in breathing

sytem

– gas is drawn through it by pts breathing spontaneously. Slide20

Comparison of the two on basis of

RESISTANCE

DETERMINANTS OF VAPORIZER OUTPUT

CAPABILITY OF THE VAPORIZER

resistance :- VOS Need not hv low resistance as gas flow can be supplied at any necessary pressure. VIS Must have low resistance because pt breathes through them

Determinants of vaporizer output :-

vaporizer output

-

conc

of vapor at outlet of vaporizer. (vo)

vaporizer

conc

:-

conc

delivered by vaporizer when fresh gas containing no

vapour

passess

through it . (

vc

)Slide21

in VOC

both

VO & VC are equal

in VIS , BOTH the VC & VO are likely to differ..the VO will be influenced by MV, uptake of agent, FGF to system and arrangement of system ..with Low FGF, VO may rise to dangerous levels. CAPABILITY OF VAPORIZER :- maximum concentration that can be delivered at highest setting of conc dial..

VIS

/ VOS used in non

rebreathing

system must have a high capability as no more anesthetic will be added to gas going to pt. but in circle system vaporizer, its not capable of delivering high

conc

, because the gas may circulate through it many times, each time picking up added vapors.VIC and VOCSlide22

RESISTANCE

PLENUM

( Latin = fullness )

Driven by positive pressure ventilation

internal resistance is high (22 cmH2O), accurately caliberatedAccurate at low flows also Eg. Boyle bottle, copper kettle, TEC vaporizers

Classification

contdSlide23

DRAW OVER

Carrier gas

drawn through the vaporizer either by the patient’s own respiratory efforts, or by a self-inflating bag or manual bellows

operate at less than, or at ambient pressureIntermittent flow, varying with different phases of inspiration, ceasing in expiration. low internal resistance

may be used in a non

rebreathing

DRAW-OVER APPARTUS,

or in CIRCLE ABSORBER SYSTEM. Eg. Goldman bottle, EMO

Slide24

ADVANTAGES

Simplicity

of concept and assembly, with inherent safety

No need for pressurised gas supply,

regulators and flow meters Minimum FiO2~21%Robust, reliable, easily serviced equipment Low cost (purchase and maintenance)Portable, suitable for field anaesthesiaDISADVANTAGESDecreasing familiarity with the technique and equipmentFilling systems not agent specific (potential advantage)Basic temperature compensation, affecting performance at extremesLess easy to observe spontaneous ventilation with self inflating bag Cumbersome in paediatric use, unless lightweight tubing is available

Drawover

anaesthesiaSlide25

flow through the vaporizing chamber.

surface area of the liquid gas interface.

temperature

time gas flow rate carrier gas composition boiling point ambient pressure :-atmospheric, intermittent back pressureFACTORS AFFECTING VAPORIZER OUTPUTSlide26

Low

pressure

:

vaporizing

chamber offers less resistance, slight increase in vapor output occurs. Deliver higher conc in vol. % but same Partial pressureHigh pressure

:

INCREASES the Density of gas, More resistance to flow of gas through the vaporizing

chamber, Decreased

vapor output (Volume Percent)

Less Effect

on partial pressure ether may boil at room temp at low atm

pressure.

Also at high pressure,

liqiud

agent may be pushed back into the

vaporiser

inlet

avoided

by maintaining a low flow of oxygen or filling the

vaporiser

after increase in pressure.

Effect of atmospheric pressureSlide27

should theoretically deliver a constant partial pressure of

anesthetic

if the ratio of gas flow through the vaporizer to bypass the flow remains the

same.

For classical plenum vapourisers, the percentage output increases roughly in proportion to the fall in barometric pressure, but a smaller partial pressure increase.TEC 6 Desflurane vapouriser behaves differently. The percentage delivered constant, so partial pressure FALLS in proportion to the fall in atmospheric pressure. The dial setting should be turned up to compensate Slide28

The increase in vaporizer output concentration due to

pulsatile

back pressure developed in the breathing system.

more

fresh gas gets compressed into vaporising chamberseen especially when-> carrier gas flow is low-> agent in vaporizing chamber is low-> dial setting is low-> pressure fluctuations are high & frequent.

Pumping effectSlide29

keep VC (

vaporising

chamber)& BC (bypass channel) of equal size/ VC small size.

Add long spiral or large diameter tube to lead to the vaporizer chamber

add check valve, increase resistance to gas flow through V.C.Exclude wicks from the area where the inlet tube joins the vaporizing chamber.Longer Outlet tubeLimit pressure transmitted to vaporizer to <10KPa above normal working pressure, conc not to increase > 20%.Minimising

pumping effectSlide30

Increased

constant pressure in vaporizer chamber

leads to decreased output

Mostly seen when

-> High flow -> Large pressure fluctuations -> Low dial settings The changes in vaporizer output caused by the pumping effect usually are greater

in magnitude that those associated with the pressurizing effect

Pressurizing effectSlide31

Pressurizing effectSlide32

INCORRECT AGENT

Low output or high output

Rx : Gas allowed to flow through it until no agent detected in the outflow,

labelling

correctly.RESISTANCETIPPINGLiquid from the vaporizing Chamber→ bypass/outlet→ high outputDrained before moving

hazardsSlide33

OVERFILLING

safety

mechanisms: design

of the filling

port, agent specific filling systemsDuring filling dial to be off FOAMING

possibility

of liquid agent getting into the

outlet.

Seen

in bubble through

vaporiser for methoxyflurane.foaming

due to silicone grease, (used as a lubricant) or solution used to test for leaks.

Hazards contd.Slide34

REVERSED FLOW

Inlet male & outlet female

Increased output

CONCENTRATION DIAL IN WRONG POSITION

CONTAMINANTS IN VAPORIZING CHAMBERPHYSICAL DAMAGEOBSTRUCTION TO FRESH GAS FLOWINTERLOCK MALFUNCTIONHazards contd.Slide35

Boyle’s bottleCopper kettle

EMO (

epstein

,

macintosh, oxford) vaporiserGoldman vaporiserOMV (oxford miniature vaporiser)CypraneVernitrolothersOlder vaporizersSlide36

Useful in remote locations like military use, as portable and simple to use (ex EMO)

Some peripheral setups still use

goldman

vaporiser

Draw over vapouriser (2 OMVs with sevoflurane) can be used in Paediatric circuit Addition of OMV with ventilator in treatment of severe asthma (Nagappan et al 2006)Relevance of older vaporisers in present timesSlide37

Parts:

(1) vaporizing bottle 300

mL

(2) Metal top incorporating controls

(3) Lever, plunger which is chrome plated (copper in case of Boyle ether bottle and absent in halothane bottle)(4) Stopper & Retaining chainConcentration calibrated, plenum typeFlowover or bubble throughNot temperature compensated

Multiple agents

Vaporizer outside

circuit

With this bottle, the maximal ether concentration would be about 50% at 20 degrees C.

Boyle’s

bottle (early 1920’s)Slide38

Developed in 1930’s: modified by Morris in 1952

measured

flow (indirect type)

temperature compensated

bubble through, plenum type agents – chloroform, ether , halothane a separate supply of oxygen from extra flowmeter passes through the vaporizer.

Oxygen broken into minute bubbles by sintered bronze

large mass of copper and attachment to machine, sufficient reservoir for

heat

Disadv

: high

vap conc if FGF dec

Copper kettleSlide39

Copper kettle : internal designSlide40

Measured flow

Bubble through

Out of system

Temperature compensated (supplied heat)

Multiple agentBody made of silicone bronze, may contain upto 600 cc of liquid agent.When used for halothane, drained periodically to prevent buildup of thymol, ether and trichlorethylene should not be allowed to stand for long.Vernitrol (based on copper kettle)Slide41

Goldman

vaporiser

(1959)Slide42

originally designed for use with dental anaesthetic apparatus

Concentration

caliberated

flow over with no wicks

multiple agents – halothane, chloroformneither temperature and level compensated nor accurately calibrated.halothane concentration

usually low (hence safe), output

is mainly influenced by gas flow rate.

VOC / VIC

small

glass bottle with metal top, inlet- outlet , contol lever at top is used to alter vapor output , capacity of 20ml , max concentration delivered

2

% ,

(higher

if

splashing, spraying of agent, if wick is used, or 2 vaporizers in series

.)Slide43

3 models of

goldman

vaporizer are :-

MARK 1:- self locking in off position

MARK 2 :- differs from mark 1 in size & shape of opening in the ports & is provided with click stops at each setting mark 1 and 2 both have three divisions btwn the on & off positions. MARK 3 :- has one less division.KOMESAROFFSimilar to the Goldman but with gradations on the glass bowl indicating volumeSlide44

Modification of Goldman

vaporizer (has wire wick gauge)

simple flow-over type

not temp compensated

capacity of 35 ml multiple agent max concentration up to 3.1 % with 4L/ min flow rate. vapor strength is controlled by means of lever stopcock. Rowbotham

vaporiserSlide45

Introduced by Epstein, Macintosh, Mendelssohn in

1966.

Vaporizer inside/outside circuit

Variables bypass

Flow over with steel wicks (cleaned with ether)Not Temperature compensated (heat sink= heat buffering)multiple agent, detachable scales (adv)

Halothane,

trilene

,

methoxyflurane

,ether,

isoflurane.particularly versatile, can be used to vaporize a number of agents with only the dial scale being changed. Oxford miniature vaporiserSlide46

Original models contained

20mls

of volatile agent, more modern ones 50mls

. not temp compensated but basic thermal buffering in the form of a small glycol (anti-freeze) reservoir within a metal heat sink. reduced vapor output at lower temperatures, maximum output

2-4% with halothane between

0-30

O

C

. Made from stainless steel, resistant to corrosion.

Metal mesh wicks increase the

output (halothane use, clogged with

thymol

)

Using two OMVs with a

drawover

system appears to be a feasible technique for the induction and maintenance of

sevoflurane

anaesthesia, thus enabling wider use of

sevoflurane

in field

anesthesia

. (study by Liu et al in 2000)

OMV contd.Slide47

Epstein macintosh

oxford

vaporiser (

emo

)Slide48

Concentration

caliberated

Flowover

with wicks

Temp compensated (metal bellows with freon vapor)Multiple agents- ether, chloroform, trilene, halothaneDia:23 cm; Ht : 24 cmWt(ether) : 6 kg; (halothane) : 12 kg0 – 20% graduations40 ml ether when fullInlet for airControl lever with transit lockIndicator to denote level of anaesthesiaTemp indicator (max eff 15-30 C)EMO contd.Slide49

Water jacket : 1250

cc

Mark I:

aluminium

water jacketMark II/III/IV: stainless steel jacketUsed with OMV for spont respOMV filled with halothane for smooth induction , maintained with ether in EMOEMO contdSlide50

EMOTRIL

(

Epstein, Macintosh, Oxford Trilene

inhaler)

Introduced in 1949. A draw over Trilene vaporizer giving 0.35 and 0.5% Trilene in air, temperature compensated, designed for unsupervised use by midwives for pain relief during labor.BRYCE-SMITH INDUCTION UNIT (BSIU)no longer manufactured. useful to facilitate induction when using the EMO ether vaporizersimple no-controls vaporizerdelivers 3 - 4 mls of halothane to precede, and assist induction with, ether.Slide51

cypraneSlide52

device for

trilene

inhalation originally

from the Queen Victoria

Hospital.Maternity patients would hold the device and inhale an air-trilene mixture.The collar of the device could be rotated to vary the concentration from about 0.22% to 0.54%. The collar can be locked.Slide53

Designed in Sydney by Dr Thomas Small, in the mid 1930's, for the provision of analgesia during

labour.

The

ether container consists of a chrome plated brass drum which holds

270mls.The control on top varies the ether concentration.Valves ensure unidirectional flow, and a separate expiratory valve is on the face mask mounting.Small’s self help ether apparatusSlide54

Diamedica

Draw-Over Vaporizer (DDV) has been developed as an alternative to the Oxford Miniature Vaporizer (

OMV)

can

function as draw-over or plenumlarger reservoir, tendency towards greater accuracy during IPPV and improved consistency of output.othersSlide55

Ohmeda Universal PAC

drawover

apparatus, a modification of an earlier series of vapour-specific

vaporizers

Caliberated, temperature compensated, flow overOxygen may be added but not necessaryclinical usage with isoflurane and enfluraneTends to over-deliver vapour, esp at low flows and at high temperaturesclinical performance during spontaneous and positive pressure ventilation satisfactoryrobust construction, relatively large capacity and thermocompensation make it suitable for field or military anaesthesia.U PAC (universal portable anesthesia complete) drawover systemSlide56

Others

Cole halothane

vaporiser

Ether bypassSlide57

Freedman inhaler for trileneSlide58

Then and nowSlide59

Thankyou