anaesthesia breathing systems,vaporizers final 2

8/14/2019 Anaesthesia Breathing Systems,Vaporizers FINAL 2

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ANAESTHESIA

BREATHING SYSTEMSDR J.O.OLATOSI FWACS

LECTURER/COSULTANTLUTH/CMUL


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PROPERTIES OF IDEAL BREATHING

SYSTEM

Simple and safe to use Delivers intended inspired gas

mixture

Permits spontaneous, manual &controlled ventilation in all agegroups.

Efficient, requiring low fresh gas flowrates

Protects patient from barotrauma


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Sturdy, compact & lightweight design

Permits the easy removal of wasteexhaled gases

Easy to maintain with minimalrunning costs


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SYSTEM RESERVOIR REBREATHING PATIENT OPEN TO

ATMOSPHERE DURING

EXP INSP

OPEN NO NO YES YES

SEMI-OPEN

YES NO YES YES

SEMI-CLOSED

YES YES(partial) YES NO

CLOSED NO YES(total) NO NO


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ADJUSTABLE PRESSURE LIMITING VALVE

(expiratory/relief/spill valve)

Allows exhaled and excess gas flowto leave the breathing system.

One way valve


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COMPONENTS

1. Three ports:- inlet- patient- Exhaust

2. Lightweight discresting on knife edgeseating

3.Spring which holdsdisc on its seating

Valve opening pressurecontrolled by dial


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MECHANISM OF ACTION

One way adjustable spring loaded valve

Valve allows gases to escape when the pressurein the breathing system exceeds the valves

opening pressure.

Spontaneous ventilation -patient generates apositive pressure during expiration causing the

valve to open

a pressure of


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During positive pressure ventilation,a controlled leak is produced byadjusting the valve dial during

inspiration.

PROBLEMS

-water vapour may condense on valve

-patient may be exposed to excessivepressure if valve is closed duringassisted ventilation.


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RESERVOIR BAG

COMPONENTS

-antistatic rubber/plastic

-latex free versions

Standard adult size is2 litres.

Paed-0.5L

Accomodates FGF during

expiration therebyserving as storage fornext insp.


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Can act as a monitor of ptsventilatory pattern during spont.Vent

Can be used to assist/control vent.


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MAPELSON CLASSIFICATION

Original classificationinto 5 groups

A-E(1954)

later a 6th was addedF.


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MAPELSON A

Components

1. Corrugated rubber or plastictubing(110-180cm in length)

2. A reservoir bag mounted at themachine end.

3.

An APL valve at the patient end.


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Mechanism of Action

As pt exhales-

initially the gasesfrom the ADS arechannelled towardsRSV bag which is

filled continuouslywith FGF

Pressure builds up

opening APL andexpelling alveolargas 1st . On nextinsp. Pt gets mix of

FGF + ADS gases


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Very efficient system forspontaneous breathing

FGF= MV 70ml/kg/min

Inefficient for controlled ventillation

Not suitable for paed.


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MAPELSON B & C

Components

-Reservoir Bag (RB)

B system corrugated tubing (CT) isattached to the bag & also serves asa reservoir

-APL valve is at pts end-FGF added just proximal to APL


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Mechanism of Action (MOA)

SV- both system inefficient. FGF 1.5-2x reqd to prevent rebreathing.

CV- B is more efficient


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MAPELSON D

Bain is co-axial versionof Map D

Lightweight but compactat pt end

-useful where access islimited eg. Head &Neck surgery.

Components

-length of co-axial

tubing (tube insidetube)

180cm (540cm MRI)


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-FGF through inner tube

-Exhaled gas through outer tube

Internal tube mounted on swivel ptsend to prvt kinking.

RV mounted at machine end

APL valve mounted at machine end


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MOA

SV- pts exhaled gases are channeled backto RB & mixes with FGF. Pressure build up

leads to opening of APL, venting ofmixture of exhaled & FGF.

FGF - 1.5-2X alveolar min. vol.150-200ml/kg/hr

Inefficient & uneconomical for use SV


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CV

More efficient

70-100ml/kg/hr-connection to ventilator possible eg

penlon nuffield 200.APL valve must

be fully closed.-Parallel version available


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Problems:

internal tube can- kink

-disconnect Movt of RB during SV not an

indication that FGF is being delivered

to patient.


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MAPELSON E & F

T- piece system

Valveless breathing system

Used for children


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MOA

Require 2.5-3X MV to prvt rebreathing

RB-visual monitor during SV

-assist/control ventilation

- provide CPAP during SV

CV performed by manual squeezing of

double ended bag.can connect reservoir tubing to penlonnuffield 200 ventilator


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Advantages-

Valveless- low resistance to breathing

Reduced dead spaceCompact/lightweight


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HUMPHREY A D E SYSTEM

Combines advantages of Map A,D,E

Efficient for both SV & CV in Adultsand children

Mode of use determined by theposition of lever mounted on theHumphrey block

Both parallel& co-axial versions exist


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Parallel version2 lengths 15mm smooth

bore tubing1.Delivers FGF

2.Transports exhaledgasesProximally they are

connected to thehumphrey block.

Distally they areconnected to a Yconnection leading tothe pt.


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Components

Humphrey block is at the machine end

APL valve

2 litre RB

Port for ventilator connection

Safety pressure relief valve

Newer devices incorporate soda limecannister


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MOA

Lever up SV mode

RV & APL valve connected as in

Mapelson A.Lever down - CV mode

RV & APL isolated from breathing

system as in EExpiratory tubing channels exhaled

gas via the ventilator port.


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SV FGF 50-60ml/kg/min adults

Children


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CIRCLE SYSTEM

Economical

loss of heat &

humidity

pollutionComponents

Soda Lime Barium hydroxide


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Soda Lime Barium hydroxide

Lime

Mesh size 4-8 4-8

Method ofhardness

Silica added Water ofcrystallization

Content CaOH,

NaOH,KOH

BaOH,

CaOH

Usualindicator dye

Ethyl violet

(whiteviolet)

Ethyl violet

Absorptivecapacity-litresof C02/100gof granules

14-23 9-18


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Components

Carbon Dioxide Absorber

- CO2 + H20 H2CO3

- H2CO3 + 2NaOH Na2 CO3 + 2H20 +Heat

Color conversion of pH indicator signalsabsorption exhaustion


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Trichloroethylene + sodalime neurotoxin

Desflurane + baralyme Carbon monoxideSevoflurane + baralyme Compound A(rats)

Amsorb- new absorber consisting of CaOH+ CaCl

-greater inertness and less degradation ofvolatile anaesthetics


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Canisters- contains granules

2 canisters fit snugly btw head-base plate

-permit more complete CO2 absorption

-placed vertically to prevent exhaled gaschanneling through unfilled portion.

-can be used for both SV + CV

-disposable units available


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Unidirectional Valves

- Mounted in see-through plasticdomes to assess functionality.

-


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Problems

Adequate monitoring of inspired 02,EtC02

& inhalational agent.

Unidirectional valves may stick & fail dueto vapour condensation.

Production of compd. A,CO.

Sodalime is corrosive Many connectionssed potential for

leaks/disconnections


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VAPORIZERS

device for adding

clinically safeconcentrations ofanaesthetic vapour to

a stream of carriergas.

Earliest Schimmelbusch mask


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Classification

A

-plenum-drawover

B

-calibrated-uncalibrated


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Components-

Vapour chamber

Flow splitting device

Splitting Ratio


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Drawover vaporizer:

-Low internal resistance to gas flow.

-Gas is drawn into vaporizer duringinspiration.

-do not require a pressurized gassupply


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Goldman

-no temp compensation

-can be used in a circle system.


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Oxford MiniatureVapourizer (OMV)

Portable

Multi-agent

Easily cleaned andserviced

Wire-gauze wick

No temperature

compensation Small heat sink

containing glycol


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EMO ether inhaler(Epstein,Macintosh, Oxford)

Robust

Water-bath heatsink

Ether bellows

temperaturecompensator

Level indicator


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Open drop techniques (ether andchloroform) - e.g. Schimmelbusch maskand Ogstons inhaler

Drop rate gives inspired concentration

Number of layers of gauze or lintimportant (wick)

Freezing may occur (latent heat) Eye protection needs to be considered

(freezing


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Plenum vaporisers-

designed for use with continuousflow of pressurised gas, and havehigh internal resistance.

- Unidirectional flow

- Include Tec series


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Boyles bottle.

Not temperature compensated

not agent specific.

The cowling over the U tube forces gas tobubble through ether when down,increasing output by increasing thegas/liquid interface.

Cools dramatically in use with a drasticdecrease in output.May need frequentrefilling while in use


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Tec 2 (Ohmeda) Halothane vaporiser

Temperaturecompensated

Bimetallic strip Series of wicks

Metal heat sink


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Tec 3-4

Flow of liquid agentinto delivery line isprevented if vaporizer

is inverted. Interlock system

Key fitting system

Tec 4-5

Increased capacity Improved filling

system


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Tec 6(Desflurane vaporizer)-req. electrical power supply

for the heating elements &control mechanisms

-desflurane heated to 39C

-system of pressuretransducers and internal &circuitary adjusts output

-5-10min warm up time


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Tec 4-5

Increased capacity

Improved filling

system


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VAPORISER SAFETY

Keyed filling devices reducing thelikelihood of filling with the wrong agent

Agent level indicators Stable mounting brackets to prevent

tipping and spillage

Correct placement in circuit: Plenum Downstream from rotameters,

upstream of oxygen


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Draw-over Upstream from self inflating bag/bellows

Interlock devices to stop the concurrent use of two

vaporisers in series, preventing contamination fromupstream to downstream vaporiser.

Correct placement in series (if no interlock): More volatile

agents (highest SVP) placed downstream

Halothane downstream to prevent thymol contamination

of others

Agent monitoring, checking that the circuit

concentrations are adequate


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Hypobaric and Hyperbaricenvironments


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FACTORS AFFECTING VAPORIZER

PERFORMANCE

SVP

Temperature-bimetallic strips,bellows

Splitting ratio- flow rate vap chamber

flow rate bypass

Surface area-wicks/helix/bubbling

Duration of use Flow characteristics

anaesthesia breathing systems,vaporizers final 2

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