Anesthetic Breathing Circuits By Dr. Ahmed Mostafa Assist. Prof. of anesthesia & I.C.U.

Anesthetic Breathing Circuits

ByDr. Ahmed Mostafa

Assist. Prof. of anesthesia & I.C.U.

Insufflation method• Definition:

It the blowing of anesthetic gases across a patient's face.

•Uses:

Pediatric inductions with inhalation anesthetics.

Maintain arterial oxygenation during brief periods of

apnea (e.g. during bronchoscopy).

Insufflation method

• Methods:

Cupped hand containing the end of the gas delivery tube.

Edinburgh face mask.

Mouth cannula.

Nasal cannula.

Simple O2 mask.

Venturi O2 mask.

Insufflation method• Advantages:

Avoids direct connection between a breathing circuit and a patient's airway.

There is no rebreathing of exhaled gases especially if the flow is high enough.

•Disadvantages:

Poor control of inspired gas concentration and depth of anesthesia.

Inability to assist or control ventilation.

No conservation of exhaled heat or humidity.

Difficult airway management during head and neck surgery.

Pollution of the operating room with large volumes of waste gas.

Open-Drop Anesthesia• Although open-drop anesthesia is not used in modern medicine, its historic

significance warrants a brief description here. A highly volatile anesthetic

most commonly ether or halothane is dripped onto a gauze-covered mask

(Schimmelbusch mask) applied to the patient's face. As the patient inhales,

air passes through the gauze, vaporizes the liquid agent, and carries high

concentrations of anesthetic to the patient.

• A modern derivative of open-drop anesthesia utilizes draw-over vaporizers that depend on the patient's inspiratory efforts to draw ambient air through a vaporization chamber. This technique may be used in locations or situations in which compressed medical gases are unavailable (e.g. developing countries and battlefields).

MAPLESON CIRCUITS

Components of Mapleson Circuits:

Breathing Tubes:

Corrugated.

Made of rubber (reusable) or plastic (disposable)

The large diameter of the tubes (22 mm)

To minimize FGF requirements, the volume of the breathing tube should

be at least as great as the patient's tidal volume.

Minimal compliance.

MAPLESON CIRCUITS

Components of Mapleson Circuits: Fresh Gas Inlet:

Adjustable Pressure-Limiting (APL) Valve (Pressure-Relief Valve, Pop-off

Valve):

APL valve controls this pressure buildup.

The APL valve should be fully open during spontaneous ventilation.

Assisted and controlled ventilation require positive pressure during inspiration to

expand the lungs.

Partial closure of the APL valve limits gas exit, permitting positive circuit

pressures during reservoir bag compressions.

MAPLESON CIRCUITS


Reservoir Bag (Breathing Bag):

Function:

Reservoir of anesthetic gas.

Method of generating positive-pressure ventilation.

MAPLESON CIRCUITS



Compliance:

• High compliance as their volume.

• Three distinct phases of reservoir bag filling are

recognizable:

MAPLESON CIRCUITS



Compliance:

i. phase I : After the nominal 3-L capacity of an adult reservoir bag is achieved.

ii. phase II: pressure rises rapidly to a peak.

iii. phase III: Further increases in volume result in a plateau or even a slight

decrease in pressure. This ceiling effect helps to protect the patient's lungs

against high airway pressures if the APL valve is unintentionally left in the

closed position while fresh gas continues to flow into the circuit.

MAPLESON CIRCUITS

Classification and Characteristics of Mapleson Circuits:

1. Mapleson A(Magill system):

MAPLESON CIRCUITS



Description:

The FGF inlet and reservoir bag are away from the

patient.

The spill valve is close to the patient.

MAPLESON CIRCUITS



Required fresh gas flow:

Spontaneous ventilation:

. Equal to minute ventilation (80 mL/kg/min).

. The most efficient.

Controlled ventilation: the least efficient.

MAPLESON CIRCUITS



MAPLESON CIRCUITS


2. Lack system(Coaxial Magill system):

MAPLESON CIRCUITS



Description:

It has two tubes with the same axis, the outer one (22 mm

diameter) through which inspiration occurs and a narrow inner

tube (7 mm diameter) through which expiration occur, so

resistance tom expiration may occur.

MAPLESON CIRCUITS





- Equal to minute ventilation (80 mL/kg/min).

Controlled ventilation: 2-3 the minute ventilation.

MAPLESON CIRCUITS



MAPLESON CIRCUITS


3. Mapleson B:

MAPLESON CIRCUITS


3. Mapleson B:

Description:

The reservoir bag is away from the patient.

The FGF inlet and spill valve are close to the patient.

MAPLESON CIRCUITS


3. Mapleson B:



- 2-3 minute ventilation.

Controlled ventilation: 2-3 minute ventilation.

Rarely used in clinical practice.

MAPLESON CIRCUITS


4. Mapleson C (Waters' to-and-fro):

Description:

The reservoir bag, the FGF inlet and spill valve are close to

the patient.

No corrugated tube.

Required fresh gas flow: as Mapleson B.

MAPLESON CIRCUITS


5. Mapleson D:

MAPLESON CIRCUITS


5. Mapleson D:

Description:

The spill valve and reservoir bag are away from the

patient.

The FGF inlet is close to the patient.

MAPLESON CIRCUITS


5. Mapleson D:




MAPLESON CIRCUITS


5. Mapleson D:


Controlled ventilation:

- 1 minute ventilation.

- The most efficient.

- It is used in adult.

MAPLESON CIRCUITS


6. Bain system:

• The Bain circuit is a popular modification of the Mapleson D system.

MAPLESON CIRCUITS


6. Bain system:

Description:

It has two tubes with the same axis, the outer one (22

mm diameter) through which expiration occurs and a

narrow inner tube (7 mm diameter) through which

inspiration occur.

MAPLESON CIRCUITS


6. Bain system:



- 1 the minute ventilation (70-80 ml/kg/min).


- 2-3 minute ventilation (200-300 mL/kg/min).

MAPLESON CIRCUITS


6. Bain system:

Advantages:

Decreases the circuit's bulk

Retains heat better than the Mapleson D circuit as a result of partial

warming of the inspiratory gas by the surrounding warmer expired gases.

Improve humidification due to partial rebreathing.

Some types of automatic ventilators can be connected to it.

MAPLESON CIRCUITS


6. Bain system:

Disadvantages:

The possibility of kinking or disconnection of the fresh gas inlet tubing. If unrecognized, it results in significant rebreathing of exhaled gas.

Large waste of gases.

MAPLESON CIRCUITS


6. Bain system:

MAPLESON CIRCUITS


7. Mapleson E (Ayre’s T piece):

MAPLESON CIRCUITS



Description:


No bag or valves are present.

MAPLESON CIRCUITS








Used in pediatric.

MAPLESON CIRCUITS



MAPLESON CIRCUITS


7. Mapleson F (Jackson Rees modification of Ayre’s T piece):

Description:


The bag is added away from the patient to allow controlled

ventilation and scavenging.

No valves are present.

MAPLESON CIRCUITS


7. Mapleson F (Jackson Rees modification of Ayre’s T piece):






The most efficient in pediatric.

MAPLESON CIRCUITS

Efficiency of Mapleson Circuits:

Breathing-circuit efficiency is measured by the fresh gas flow required to

eliminate, as much as possible, CO2 rebreathing.

Because there are no unidirectional valves or CO2 absorption in Mapleson

circuits, rebreathing is prevented by venting exhaled gas through the APL

valve before inspiration. There is usually some rebreathing in any

Mapleson circuit. The flow through the circuit controls the amount. To

attenuate rebreathing, high fresh gas flows are required.

THE CIRCLE SYSTEM

- The carbon dioxide absorber canister is labeled (C).

- The breathing bag (B).- Inspiratory valve (Vi).- Expiratory valve (Ve).- pressure relief valve

(V).- Fresh gas supply (F).

THE CIRCLE SYSTEM

Components of the Circle System:

THE CIRCLE SYSTEM

1. FGF Source.

2. Unidirectional valves.

3. Inspiratory and expiratory corrugated tubes.

4. AY- piece connector.

5. Adjustable pressure limiting valve.

6. A reservoir bag.

7. Ventilator bag switch.

8. Carbon Dioxide Absorbent.

THE CIRCLE SYSTEM

THE CIRCLE SYSTEM

Carbon Dioxide Absorbent

Types:

1. Soda lime.

2. Bara Lime.

3. Amsorb.

THE CIRCLE SYSTEM


Types:1. Soda lime:

Is the more common absorbent and is capable of

absorbing up to 23 L of CO2 per 100 g of

absorbent.

THE CIRCLE SYSTEM


Types:1. Soda lime:Its reactions are as follows:

CO2 + H2O H2CO3.

H2CO3 + 2NaOH Na2CO3 + 2H2O + Heat. (Fast reaction)

Na2CO3 + Ca(OH)2 CaCO3 + 2NaOH. (Slow reaction)

THE CIRCLE SYSTEM


Types:

2. Bara Lime: Its reactions are as follows:

THE CIRCLE SYSTEM

Carbon Dioxide AbsorbentComparison of Soda Lime and Barium Hydroxide Lime

Soda Lime Barium Hydroxide Lime

Mesh size1 4–8 4–8

Method of hardness Silica added Water of crystallization

Content Calcium hydroxide (94%) Barium hydroxide (80%)

Sodium hydroxide (5%) Calcium hydroxide

Potassium hydroxide (1%)

Usual indicator dye Ethyl violet Ethyl violet

Absorptive capacity (liters of CO2/100 g granules) 14–23 9–18

water content 14–19%

THE CIRCLE SYSTEM


Indicator Dye Changes Signaling Absorbent Exhaustion

Indicator Color when Fresh Color when Exhausted

Ethyl violet White Purple

Phenolphthalein White Pink

Clayton yellow Red Yellow

Ethyl orange Orange Yellow

Mimosa 2 Red White

THE CIRCLE SYSTEM

Carbon Dioxide AbsorbentTypes:

3. Amsorb:

- Has greater inertness than soda lime or barium hydroxide lime.

- less degradation of volatile anesthetics.

- It is consisting of:

Calcium hydroxide, Calcium chloride, Calcium sulfate and Poly-

vinyl-pyrrolidone added to increase hardness.

THE CIRCLE SYSTEM

Carbon Dioxide Absorbers:

The granules of absorbent are

contained within one or two

canisters that fit snugly

between a head and base

plate.

THE CIRCLE SYSTEM

Performance Characteristics of Circle System:

Fresh Gas Requirement:

The circle system prevents rebreathing of CO2 at

low fresh gas flows that (≤ 1 L) or even fresh gas

flows equal to the uptake of anesthetic gases and

oxygen by the patient and the circuit itself.

THE CIRCLE SYSTEM



At fresh gas flows greater than 5 L/min,

rebreathing is so minimal that a CO2 absorber is

usually unnecessary.

THE CIRCLE SYSTEM



With low flows, concentrations of O2 and

inhalation anesthetics can vary markedly between

fresh gas and inspired gas.

THE CIRCLE SYSTEM



The greater the fresh gas flow rate, the less time it

will take for a change in fresh gas anesthetic

concentration to be reflected in a change in

inspired gas anesthetic concentration.

THE CIRCLE SYSTEM



Higher flows speed induction and recovery,

compensate for leaks in the circuit, and decrease

the risks of unanticipated gas mixtures.

THE CIRCLE SYSTEM


Dead Space:

Any increase in dead space must be

accompanied by a corresponding increase in

tidal volume if alveolar ventilation is to

remain unchanged.

THE CIRCLE SYSTEM


Dead Space:

Because of the unidirectional valves, apparatus

dead space in a circle system is limited to the area

distal to the point of inspiratory and expiratory gas

mixing at the Y-piece.

THE CIRCLE SYSTEM


Resistance:

The unidirectional valves and absorber increase circle system

resistance, especially at high respiratory rates and large tidal

volumes. Nonetheless, even premature neonates can be successfully

ventilated using a circle system.

THE CIRCLE SYSTEM


Humidity and Heat Conservation:

• the heat and humidity of inspired gas depend on

the relative proportion of rebreathed gas to fresh

gas.

THE CIRCLE SYSTEM


Humidity and Heat Conservation:

High flows are accompanied by low relative humidity,

whereas low flows allow greater water saturation.

Absorbent granules provide heat and moisture in the

circle system.

THE CIRCLE SYSTEM


Bacterial Contamination:

• There is slight risk of microorganism retention in circle

system components. For this reason, bacterial filters are

sometimes incorporated into the inspiratory or expiratory

breathing tubes or at the Y-piece.

THE CIRCLE SYSTEM

• Advantages of the circle system:

1.More economic.

2.Preserve heat and humidity.

3.Decrease the risk of pollution of the operating

room.

THE CIRCLE SYSTEM

• Disadvantages of the Circle system:

1. Greater size and less portability.

2. Increased complexity.

3. Higher risk of disconnection or malfunction

4. Increased resistance.

5. The difficulty of predicting inspired gas

concentrations during low fresh gas flows.

THE CIRCLE SYSTEM

• Monitoring during low anesthesia:

1. O2 analyzer: to measure inspired O2 concentration.

2. Capnography: to measure end-tidal CO2.

3. Multi-gas analyzer: to measure anesthetic gas

concentration.

THE CIRCLE SYSTEM

• Disadvantages of low flow and closed circuit:

I. Disadvantages of low FGF:

- Unpredictable concentration of O2 and volatile anesthetics.

- Accumulation of foreign trace gases as:

Methane from the intestine , acetone from the liver, ethanol in

alcoholic patients, carbon monoxide in heavy smokers.

- Does not compensate for leaks.

THE CIRCLE SYSTEM


II. Disadvantages of CO2 absorbents ( The interaction between

CO2 absorbent and inhalational anesthetics):

a) Haloalkene toxicity:

Halothane degradation BCDFE which is nephrotoxic in rats.

Sevoflorane degradation Compound A which is nephrotoxic in rats.

THE CIRCLE SYSTEM




b) Carbon monoxide toxicity:

- Cause: Dry absorbent.

- Occur with desflurane, enflurane, or isoflurane.

THE CIRCLE SYSTEM





- The incidence of carbon monoxide formation is not known but is

probably greater than thought.

- Cases of severe carbon monoxide poisoning have been reported.

THE CIRCLE SYSTEM





Reported at:

- The first general anesthetic of the day and on Monday morning.

- A little-used machine in a remote location.

THE CIRCLE SYSTEM



CO2 absorbent and inhalational anesthetics)

III. Disadvantages of circuit system: discussed before.

RESUSCITATION BREATHING SYSTEMS


• Resuscitation bags (AMBU bags or bag-mask

units) are commonly used for emergency

ventilation. A resuscitator is unlike a Mapleson

circuit or a circle system because it contains a

non-rebreathing valve.


• Advantages:

- Simple.

- Portable.

- Ability to deliver almost 100% oxygen.


• Disadvantages:

- They require high fresh gas flows to achieve a

high FIO2.

- The maximum achievable tidal volumes are less

than those that can be achieved with a system that

uses a 3-L breathing bag.

DR. AHMED MOSTAFA

Thank you

Anesthetic Breathing Circuits By Dr. Ahmed Mostafa Assist. Prof. of anesthesia & I.C.U.

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Transcript of Anesthetic Breathing Circuits By Dr. Ahmed Mostafa Assist. Prof. of anesthesia & I.C.U.