MAPLESON BREATHING SYSTEMS

DR RESHMA AMBULKAR

DR DEEPAK CHAVAN

Mapleson A (Magill‘s) System

• The Mapleson A system was designed by Sir Ivan Magill in the 1930

• The Mapleson A or Magill system is good for spontaneous breathing patients, so the fresh gas flow can be lower.

• However as the APL valve is close to the patient, it is difficult to use.

• It consist of a three-way T-tube connected to the fresh gas outlet a reservoir bag and a corrrugated tube.

• The other end of the reservoir tube is connected to the patient and a spring-loaded expiratory valve.

• Corrugated rubber or plastic tubing: 110-130 cm in length.

• Reservoir Bag at Machine end.

• APL valve at the patient end.

•

• Tube volume > Tidal volume.

Mapleson A : Functional Analysis

Inspiration – Gas inhaled from reservoir bag during inspiration & RB collapses

Expiration – During early phase of expiration, the reservoir bag is not full & hence pressure within the system does not increase.Exhaled gas (first portion is dead space gas) passes back towards the reservoir bag.

Towards the later part of expiration , the bag fills further & the pressure within the system increases.This results in the opening of expiratory valve & venting of alveolar gas.

Expiratory pause - Fresh gas washes the expired gas out of the reservoir tube, filling it with fresh gas for the next inspiration.

Rebreathing of alveolar gas can be prevented if the fresh gas flow = patient's minute ventilation.

However, the last gas to be washed out of the circuit is dead space gas, which consists of warmed and humidified fresh gas, and no CO2. If some rebreathing of this dead space gas is accepted, a flow approximating to around 70% of the minute volume can be used:

Controlled Ventilation:

• To facilitate IPPV the expiratory valve has to be partly closed.

• During inspiration the patients gets ventilated with FG and part of the FG is vented through the valve after sufficient pressure has developed to open the valve.

• During expiration , the FG from the machine flows into the reservoir bag and all the expired gas ( i.e. dead space and alveolar gas flows back into the corrugated tube till the system is full.

• During the next inspiration the alveolar gas is pushed back into the alveoli followed by the fresh gas.

• When sufficient pressure is developed, part of the expired gas and part of the FG escape through the valve.

• This leads to considerable rebreathing as well as excessive wastage of fresh gas .

• Hence these system are inefficient for controlled ventilation.

Advantages:

• Best among all Maplesons systems for spontaneous ventilation

• Minimal wastage of gases during spontaneous ventilation

Disadvantages:

• Not efficient for controlled ventilation.

• Wastage of gases & operation theatre pollution.

• Expiratory valve required –produces slight resistance during expiration.

• Expiratory valve is heavy(Headbrink valve).

• Expiratory valve is near patient end inconvenient to use especially in head & neck surgeries.

• Not suitable for paediatric use.

Mapleson A – Lack Modification

• A co-axial modification of the Mapleson A system.

• Designed to facilitate scavenging of expired gas & make more efficient for controlled ventilation

• 1.6 m in length

• FGF through outside tube ( 30mm), exhaled gases from inner tube.

• Inner tube wide in diameter (14 mm) to reduce resistance to expiration(1.6 cm H2O).

• Reservoir bag at machine end

• APL valve at machine end.

• The Lack circuit is essentially similar in function to the Magill, except that the expiratory valve is located at the machine-end of the circuit, being connected to the patient adapter by the inner coaxial tube.

• Inspiration - The valve closes and the patient inspires fresh gas from the outer reservoir tube.

• Expiratory pause - Fresh gas washes the expired gas out of the reservoir tube, filling it with fresh gas for the next inspiration.

• Expiration - The patient expires into the reservoir tube. Towards the end of expiration, the bag fills and positive pressure opens the valve, allowing expired gas to escape via the inner exhaust tube

Advantages

• The location of the valve is more convenient, facilitating intermittent positive pressure ventilation and scavenging of expired gas.

Disadvantages

• In common with other co-axial systems, if the inner tube becomes disconnected or breaks, the entire reservoir tube becomes dead-space.

• This can be avoided by use of the 'parallel Lack' system, in which the inner and outer tubes are replaced by conventional breathing tubing and a Y-piece:

Mapleson B System

• The Mapleson B system features the fresh gas inlet near the patient, distal to the expiratory valve.

• The expiratory valve opens when pressure in the circuit increases, and a mixture of alveolar gas and fresh gas is discharged.

• During the next inspiration, a mixture of retained fresh gas and alveolar gas is inhaled.

• Rebreathing is avoided with fresh gas flow rates of greater than twice the minute ventilation for both spontaneous and controlled ventilation.

Mapleson C system• This circuit is also known as Water’s circuit.

• It is similar in construction to the Mapleson B , but the main tube is shorter.

• A FGF equal to twice the to twice the minute ventilation is required to prevent rebreathing.

• CO2 builds up slowly with this circuit.

• Mapleson B &C : In order to reduce rebreathing of alveolar gas FG entry was shifted to near the patient.

• This allows a complete mixing of FG and expired gas.

• The end result is that these system are neither efficient during spontaneous nor during controlled ventilation.

Mapleson D System

• It consists of fresh gas inlet nearer the patient end , a corrugated rubber tubing one end which is connected with expiratory valve and then reservoir bag.

• It is mainly used for assisted or controlled ventilation

• During the controlled ventilation there is little chance of rebreathing.

• The FGF which enters during expiratory pause accumulates in the patient end is forced during the inflation.

• In spontaneous breathing during inspiration the patient will inhale the fresh gas & gas in corrugated tube depending on FGF, TV, length of expiratory pause & volume of corrugated tube.

• Rebreathing can be minimized by increasing FGF 2-3 times the MV.

• For an adult 15L/min FGF which seems uneconomical is required.

• In some cases 250 ml/kg/min required to prevent rebreathing.

• In principal it is modification of the system used by Macintosh and Pask during Second World War to administer anaesthesia.

• It was introduced by Bain and Spoerel in 1972

• It is a modification of Mapleson D system.

• It is a coaxial system in which fresh gas flows through a narrow inner tube within outer corrugated tubing

• It functions like T-piece except that tube supplying FG to the patient is located inside the reservoir tube.

Bain circuit

Specifications:-

• Length-1.8 meters.

• Diameter of outer tube-22mm(transparent,carriesexpiratory gases)

• Diameter of inner tubing-7 mm(inspiratory)

• Resistance-Less than0.7 cmH2O

• Dead space-Outer tube upto expiratory valve( around 500ml=TV)

• Flow rates-100-150 ml/kg/min for controlled ventilation. Average 300 ml/kg/min for spontaneous ventilation

Bain system (Mapleson D)- Functional Analysis

Spontaneous respiration:

• The breathing system should be filled with FG before connecting to the patient.

• When the patient takes an inspiration, the FG from the machine , the reservoir bag and the corrugated tube flow to the patient.

• During the expiration there is a continuous FGF into the system at the patients end .The expired gas gets continuously mixed with the FG as it flows back into corrugated tubing and the reservoir bag

• Once the system is full the excess gas is vented to the atmosphere through the valve situated at the end of the corrugated tube near the reservoir bag.

• During the expiratory pause the FG continues to flow and fill the proximal portion of the corrugated tube while mix gas is vented through valve.

• During the next inspiration , the patient breathes FG as well as mixed gas from the corrugated tube.

• It is calculated and clinically prove that FGF should at least 1.5- 2 times the patient’s MV

• Controlled ventilation :

• To facilitate intermittent positive pressure ventilation, the expiratory valve has to be partly closed so that it opens only after sufficient pressure has developed in the system.

• When the system is filled with fresh gas, the patient gets ventilated with the FGF from the machine, corrugated tubing and the reservoir bag.

• During expiration expired gas continuously gets mixed with FG that is flowing into the system at the patient end.

• During the expiratory pause the FG continues to enter the system and pushes the mixed gas towards the reservoir.

• When next inspiration is initiated , the patient gets ventilated with the gas in the corrugated tube i.e.amixture of FG, alveolar gas and dead space gas.

• As the pressure in the system increases,APL valve open and the contents of reservoir bag are discharged into the atmosphere.

ADVANTAGES OF BAIN'S SYSTEM

• Light weight.• Minimal drag on ETT as compared to Magill's circuit.• Low resistance.• As the outer tube is transparent, it is easy to detect any kinking

or disconnection of the inner fresh gas flow tube.• It can be used both during spontaneous and controlled

ventilation and change over is easier.• It is useful where patient is not accessible as in MRI suites.• Exhaled gases do not accumulate near surgical field, so risk of

flash fires is abolished.• Easy for scavenging of gases as scavenging valve is at machine

end of the circuit.• Easy to connect to ventilator.• There is some warming of the inspired fresh gas by the exhaled

gas present in outer tubing.

DISADVANTAGES OF BAIN'S SYSTEM

• Due to multiple connections in the circuit there is a risk of disconnections.• Wrong assembling of the parts can lead to malfunction of the circuit.

• Theatre pollution occurs due to high fresh gas flow. However, it can be prevented by using scavenging system.

• Increases the cost due to high fresh gas flows.

• There can be kinking of the fresh gas supply inner tube blocking the fresh gas supply leading to hypoxia

• There can be crack in the inner tube causing leakage

• Case report available about the defect in metal head so that fresh gas and exhaled gas mix and entire limb becomes dead space

• It cannot be used in paediatric patients with weight less than 20 kg.

•Mapleson D system is checked for leaks by occluding the patient end, closing the APLvalve and pressurizing the system. The APL valve is then opened. The bag should deflateeasily if the valve is working properly. Outer tube integrity should also be checked byfollowing the simplest innovative method. Wet the hands with spirit. Blow air through thetube. Wipe the tube with wet hands. Leak will produce chillness in the hands.

•For checking integrity of inner tube of Bains system, a test is performed by setting a lowflow on the oxygen flowmeter and occluding the inner tube with a finger or barrel of asmall syringe at the patient end while observing the flow meter indicator. If the inner tubeis intact and correctly connected, the indicator will fall.

•Pethicks test - To check the integrity of the inner tube, activate the oxygen flush andobserve the bag. Due to venturi effect the high flow from the inner tube at the patient endwill create a negative pressure in the outer exhalation tubing and this will suck gas fromthe bag and bag will deflate. If the inner tube is not intact, this maneuver will cause thebag to inflate slightly.

Checking the circuit

Mapleson E and F

• Valveless breathing system used for children upto 30 kg.

• Suitable for spontaneous and controlled ventilation

• Components:-

• - T shaped tubing with 3 ports.

• -FGF delivered to one port

• -2 nd port goes to patient & 3rd to reservoir tube.

Mapleson E OR Ayre’s T- PIECE

• Introduced by Phillips Arye in 1937.

• Belongs to Mapleson E.

• Available as meatllic / plastic.

• Length – 2 inches.

• Parts – inlet, outlet, side tube.

• Inlet size-10 mm, outlet size-10mm metallic &15 mm plastic

Advantages• Simple to use , Light weight .

• No dead space , no resistance.

• For pediatric patients less than 20 kgs.

• Expiratory limb is attached to the outlet of T piece.-

• It should accommodate air space equal to 1/3 rd of TV.

• If too short – air dilution in spont. Breathing patients & patient become light.

• 1 inch of expiratory tube can accommodate 2-3 ml of gas.

• Fresh Gas Flows – 2- 3 times MV

Dis advantages:

• High flow rates are required.

• Loss of heat & humidity.

• Risk of accidental occlusion of expiratory limb- risk of increased airway pressure & barotrauma to lungs.

Mapleson F OR Jackson Rees Circuit

• It is a modification of Mapleson E by Jackson Rees and is known as Jackson Rees modification.

• It has a 500 ml bag attached to the expiratory limb.

• This bag helps in respiratory monitoring or assisting the respiration.

• It also helps in venting out excess gases.

• The bag has a hole in the tail of the bag that is occluded by using a finger to provide pressure.

• The bags with valve are also available.

• It is used in neonates, infants, and paediatric patients less than 20 kg in weight or less than 5 years of age.

• Technique of useFor spontaneous respiration:

The relief mechanism of the bag is left fully open.

• For controlled respiration:

The hole in the bag can be occluded by the user during inspiration and ventilation is done by squeezing the bag.

• Functional analysis

• It also functions like Mapleson D system.

• The flows required to prevent rebreathing are 2.5-3.0 times minute volume during spontaneous ventilation and 1.5 to 2 times the minute volume during controlled ventilation.

• In this system, during expiration fresh gas and exhaled gas will collect and mix in the bag.

• The next inspiration results in patient inhaling fresh gas both direct from inlet and from expiratory part of the circuit as in Mapleson E.

• During expiratory pause the expired gases are replaced by fresh gas in the expiratory limb.

• Observation of bag movements helps in assessing respiration during spontaneous breathing.

• It also allows controlled ventilation by squeezing the bag.

• Heat and moisture exchanger should not be used with Mapleson E and F during spontaneous respiration as it increases resistance.

• So most of the fresh gas will enter expiratory limb leading to wastage of fresh gases and delaying induction by inhalation agents.