mapleson circuits

MAPLESON CIRCUITSBy, Dr. Arun KumarDept of AnesthesiologyColumbia Asia Referral Hospital,Bangalore.

DEFINITION Circuit: a round course. Breathing circuit: a pathway in which

volatile agents and oxygen is delivered and Co2 is removed, 2types non-circle, circle.

Co Axial: it is where these is two coduits for inhaled and exhaled gases, where one coduit is inside the other.

Magills circuit: a circuit in which has reservoir bag a corrugated tube and spring loaded expiratory valve, rebreathing prevented by keeping fresh gas flow more than the patients minute respiratory volume.

Mapleson circuits: a circuit in which the fresh gas flow is used to remove the exhaled Co2 .

ADVANTAGES/NEED

Simple, inexpensive and rugged, parts easy to dismantle and sterilize.

Variation in minute volume affects end tidal co2 less than in circle systems.

In co axial, warm expired gas heats the inspiratory limb.

Resistance low at flows in practice. Lightweight, easy to position. Compression and compliance loss less. Change in FGF, rapid change in ins., gas

composition. No co2 abs, possible toxic byproducts not

formed.

HISTORY 1954 Mapleson studied and described 5

different semiclosed anesthetic breathing systems.

These are refered as mapleson systems A-E.

Later on Willis et al, added one more system Mapleson F.

MAPLESON A(MAGILL MODIFICATION)

MAPLESON A

Differs from other circuits, fresh gas flow is not at the patient’s end but on the other side.

At the reservoir bag, a corrugated rubber tubing connects the bag to the patient’s end where there is a adjustable pressure valve.

Lacks modification: in this he has added a expiratory limb in the tube.

makes adjusting gases easy but increases the work of breathing.

MAPLESON A

technique of use: For spontaneous breathing, the apl valve is

left open. For controlled ventilation the valve is half

closed, so that when given positive pressure adequate expansion of lungs is achieved.

Spontaneous respiration: As the patient exhales, first dead space gas

then alveolar gas flows towards the bag, the same time fresh gas flows into the bag.

When bag pressure is full APL valve opens.

MAPLESON A

Fresh gas flow reverses the direction of exhaled gas which vents out through the APL valve.

In the inspiration end, first gas is alveolar gas, then dead space gas, finally fresh gas flow.

Controlled ventilation: during exhalation the pressure in the system is low and no gas escapes through APL valve, unless bag distends, all exhaled gas remains in the tubing.

at inspiration most of the gases are re breathed into the system.

MAPLESON B

MAPLESON B

The fresh gas inlet and APL valve is near patient’s end.

Technique of use: for spontanoeus APL valve is left open.

in controlled ventilation APL is closed sufficiently to allow inflation of lungs.

Spontaneous: as Pt exhales the gas moves through the corrugated tube with FGF, when bag fills up, APL valve open exits exhaled gas with little FGF. On inspiration valve closes, FGF and gas from the tubing is taken in.

MAPLESON B

To prevent rebreathing FGF must be equal to peak inspiratory flow(20-25l/min).

Controlled : similar to Mapleson A but more efficient since FGF is near patient end.

a fresh gas flow of 2- 2.5 times minute volume is recommended.

MAPLESON C

MAPLESON C

Similar to Mapleson B, but without the corrugated tubing.

Technique is similar to the B system.

MAPLESON D

MAPLESON D

Mapleson D,E,F all have T piece at the patient end, all function similiarly.

classic form: a length of tubing connects T piece to the APL valve and reservoir bag next to it.

Bain modification: fresh gas supply runs coaxially inside the corrugated tubing, and ends at a point where the fresh gas would have flown if classic mapleson D was used.

The outer tubing is clear so the inner tube can be inspected.

MAPLESON D

technique of use: spontaneous: the APL valve is left open and the

gas is vented. Assisted: the valve is partially closed, and the

bag squeezed.

Mech of use: Spontanoeous: pt., exhaled gas chanelled back

to reservoir where it gets mixed with fresh gas flow.

FGF required is 150-200ml/kg/min. 1.5-2 times alveolar minute volume.

Inefficient and uneconomical.

Controlled ventilation: efficient flow of 70-100ml/kg/min maintains normocapnia.

Exhalation gas flows from pt to tubing, even fresh gas enters tubing.

Inspiration: fresh gas and tubing air flows, if FGF is low then exhaled gas may be inhaled.

Can be connected to ventilator.

MAPLESON E (AYRE’S T- PIECE)

MAPLESON E

This is used in children upto 25-30kg body weight.

A T shaped tubing with 3 open ports, one fresh gas, second patient end, third reservoir tubing.

Designed to provide spontaneous ventilation, since there is almost no resistance to expiration.

Not popular as there is no scope for cotrol of gas flows.

MAPLESON E

Advantage: lightweight. minimal resistance to flow can be used for spont/ controlled

vent. simple design.

Disadvantage: exhaust gas not easy to scavenge.

obs to expiratory limb : high pressure to patient.

no scope to artificially ventilate pts.

MAPLESON F (JACKSON REES MOD)

MAPLESON F

It is mapleson E with a reservoir bag added at the expiratory limb.

Hence monitoring patient’s breathing was possible.

reservoir bag has a valve outlet at the end.

Using which for spontaneous vent can be kept open,

While for controlled can be partially closed.

DISADVANTAGES.

Requires high gas flows. Due to this inspired heat and humidity tends

to be low.

In mapleson A,B,C Apl valve is in the pt’s end: inaccessible.

In mapleson E,F difficult to scavenge.

REFERENCES

Dorsch, understanding of anaesthetic equipments. Seventh edition.

Whylie, a practice of Anesthesia. Seventh edition.

Al- shaikh, Stacey, essentials of Anesthetic equipments. Third edition.

World wide web.