This document discusses anesthesia circuits, covering their definition, history, functions, classifications, and components. It details various types of circuits such as Mapleson A to F, their advantages, disadvantages, and methods for circuit integrity checks. The document also highlights the importance of effective gas delivery, CO2 elimination, and maintaining the patient's warmth and humidity during anesthesia.

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ANAESTHESIA
CIRCUITS
Presenter: Dr. V.Hemant (PG 1)
Moderator: Dr. Pooja Ahuja (AP)

2. OBJECTIVES
o Definition
o History
o Function
o Classification
o Components
o Functional Analysis
o Circuit Checks
o Closed Circuit

3. DEFINITION
o An Assembly of components connecting
patient’s airway to anesthesia machine.
o Delivers the anesthetic gas mixture from
anesthesia machine to patient’s alveoli in a
• set concentration
• shortest possible time
• minimal rebreathing
• minimal resistance

4. HISTORY
Sir Ivan Whiteside Magill – 1917
(Mapelson A)

5. Ralph Milton Waters - 1927
(To and Fro circuit)

6. Brian Sword – 1930
(The Circle System)

7. Thomas Philip Ayre – 1939
(Mapelson E)

8. Gordon Jackson Rees – 1952
(Mapelson F)

9. William W Mapelson -1954
(Classification of Mapelson Circuits)

10. ESSENTIAL FUNCTIONS
o Delivery of anesthetic gases mixture.
o Effective elimination of CO2.
o Conservation of heat and moisture.
o Used in spontaneous/assisted/ controlled
respiration.

11. IDEAL CIRCUIT
o Quick & accurate delivery of anesthetic gas mixture
o Effective elimination of carbon dioxide
o Conserve heat & moisture
o Minimal resistance
o Minimal dead space
o Most economic
o Easy to use & sterilize

12. CLASSIFICATION
DRIPP’S CONWAY

13. DRIPP’S CLASSIFICATION
o Open - no reservoir and no rebreathing.
o Semi open - good reservoir and no rebreathing.
o Semi closed - good reservoir and partial
rebreathing.
o Closed - total rebreathing.

14. MODIFIED CONWAY’S
CLASSIFICATION
Without CO2 absorption
o Unidirectional flow : Mapleson's
A with non rebreathing valve
o Bidirectional flow : Mapleson’s
A -F
• Afferent reservoir system
- Mapleson A, B ,C
• Efferent reservoir system
- Mapleson D, E, F
With CO2 absorption
Unidirectional flow and
bidirectional flow
o Unidirectional flow -
Closed circuit with
absorber
o Bidirectional flow -
Water’s To and Fro
circuit

15. COMPONENTS OF MAPLESON
SYSTEMS
22/02/2020
ADJUSTABLE
PRESSURE
LIMITING VALVE
CONNECTORS
AND
ADAPTERS
BREATHING
TUBES
RESERVOIR
BAG

16. BREATHING TUBES
o Large Bore: minimal resistance
o Corrugated: flexibility, prevents kinking and produces
turbulent flow (better mixing of gases)
o Act as reservoir in some circuits
o Adult: 22mm wide
o Paediatric: 15 mm wide
o Silicone/rubber/plastic

17. ADJUSTABLE PRESSURE
LIMITING VALVE
o Heidbrink valve i.e. pressure adjusted knob, disc and
spring valve.
o A/k/a pop-off valve, exhaust valve, scavenger valve,
relief valve, expiratory valve, over-spill valve etc.
o One way, adjustable, spring-loaded valve.
o Release of exhaled waste gases and fresh gas flows when
the pressure within the breathing system exceeds the
valve’s opening pressure.
o Essential in controlled ventilation.

18. ADJUSTABLE PRESSURE
LIMITING VALVE

19. RESERVOIR BAG
o Made of antistatic rubber
o Size: 3L, 2L,1L, 0.5L
o Accommodates fresh gas flow during expiration,
reservoir for peak inspiratory flow (3-4MV)
o Most distensible part of the breathing system: prevents
Barotrauma
o Used to assist or control the ventilation
o Monitors patient’s ventilatory pattern

20. CONNECTOR / ADAPTER
o To connect various parts of breathing system
o Extend the distance between patient and breathing system
o Allow more flexibility for maneuvering
o Increase dead space and resistance
o Increased chances of disconnection

21. MAPELSON CLASSIFICATION

22. MAPELSON A

23. MAPELSON A
o Corrugated hose length 110 cms
o Volume 500 ml
o FGF for spontaneous ventilation – 1 MV
o FGF for controlled ventilation – 3 times MV
o Ideal for spontaneous ventilation
o Worst for controlled ventilation

24. FUNCTIONAL ANALYSIS
Spontaneous Breathing:
• FGF equal to one minute
ventilation for spontaneous
ventilation
• Preferred for spontaneous
ventilation
• Negligible rebreathing (70 -
85ml/kg/min or 5-6 L/min FGF)

25. FUNCTIONAL ANALYSIS
Controlled Ventilation:
• APL valve partially closed
• FGF 3 times Minute Ventilation
for controlled ventilation
• Excessive rebreathing
• Waste of gases
• Not preferred for controlled
ventilation

26. LACK’S MODIFICATION
o Expiratory limb, from the patient end to the APL valve at the
machine end (1971)
o • Scavenging of gas - prevent theatre pollution.
o • Disadvantage: Increases the work of breathing.
o Available in two arrangements:
• Parallel tube.
• Coaxial configuration: expiratory limb runs concentrically inside
inspiratory limb.

27. LACK CIRCUIT

28. CHECKING OF CIRCUIT
Mapelson A
• Occlude the patient end,
close the APL valve and
pressurize the system.
• APL valve: by opening and
closing it.
Lack system (Integrity of the inner tube)
• Attach a tracheal tube to the inner tubing
at patient end. Blow down the tube with
the APL valve closed. There will be
movement of the bag if there is leak
between the two tubes.
• Occlude both the limbs at patient
connection with the valve open and then
squeeze the bag. If there is leak in the
inner limb, gas will escape through the
valve and bag will collapse.

29. MAPELSON B & C
o Similar to each other
o FGF & APL near patient end
o Reservoir Bag away from patient
o Mapleson’s C: NO corrugated breathing tube
o Mapleson’s B not used in routine practice
o Mapleson’s C: emergency resuscitation
o Very High FGF (20-25L/min): OT pollution, Wastage, Non
economical

30. MAPELSON D
o Ideal for controlled ventilation
o FGF for controlled ventilation – 1 MV
- for spontaneous ventilation – 2 times MV
o T piece :
 one end FGF tube
 other end wide bore corrugated tube having reservoir
bag at the end
o 6mm diameter tube supplies FGF from machine end.

31. BAINS CIRCUIT
o Fresh gas supply tube runs coaxially inside the
corrugated tubing.
o Diameter
 outer tubing: 22 mm
 inner tube is 6 mm.
o Length:1.8m (volume >500 ml)
o Outer tube: transparent so that inner tube can be seen
for any disconnection or kinking.

33. FUNCTIONAL ANALYSIS
Spontaneous respiration
o APL valve fully open
o Minimal rebreathing
o FGF - 1.5-2 times of Minute
Ventilation
o Factors influence
rebreathing
• FGF
• Respiratory rate
• Expiratory pause
• Tidal volume

34. FUNCTIONAL ANALYSIS
Controlled Ventilation
o APL valve partially closed
o Minimal rebreathing
o FGF - 1.5-2 times Minute
Ventilation
o Factors influence
rebreathing
• FGF
• Respiratory rate
• Expiratory pause
• Tidal volume

35. ADVANTAGES OF BAIN’S
CIRCUIT
o Light weight : Minimal drag.
o Low resistance.
o Used for both spontaneous and controlled ventilation.
o Length: long where patient is not accessible as in MRI
suites.
o Minimal rebreathing: OT pollution.
o Warming of the inspired fresh gas by the exhaled gas
present in outer tubing.

36. DISADVANTAGES OF BAIN’S
CIRCUIT
o Multiple connections: risk of disconnections.
o Wrong assembling: malfunction of the circuit.
o High fresh gas flow: theatre pollution & increased cost.
o Damaged fresh gas supply inner tube blocking:
Hypoxia/Hypercarbia
o Cannot be used in paediatric patients (weight less than
20 kg)

37. CHECKING MAPELSON D
o Leaks: Occlude the patient end, close the APL valve
and pressurize the system. Open the APL Valve: The
bag should deflate easily.
o Outer tube integrity: Wet the hands with spirit. Blow
air through the tube. Wipe the tube with wet hands.
Leak will produce chillness in the hands.

38. CHECKING BAIN’S CIRCUIT
o Foex Crompton Smith Test:
 Integrity of inner tube
 Set flow on the oxygen flowmeter (4-6l/min).
 Occlude the inner tube at the patient end.
 Observe the flow meter indicator.
If the inner tube is intact and correctly connected, the
indicator will fall.

39. CHECKING BAIN’S CIRCUIT
o Pethik’s test:
• Activate the oxygen flush and observe the bag.
• Due to venturi effect the high flow from the inner
tube at the patient end will create a negative pressure
in the outer exhalation tubing and this will suck gas
from the bag and bag will deflate.
• If the inner tube is not intact, the bag will inflate
slightly.

40. MAPELSON E
o Ayre’s T piece: Philips Ayre 1937
o Components:
• light metal tube 1 cm in diameter,
• 5 cm in length with a side arm
o Functional Analysis:
• Functions as a non-rebreathing system.
• FGF enters through the side arm
• Expired gas is vented into the atmosphere
• No rebreathing.
• Requires high FGF

41. o Reservoir tubing at the expiration port (volume 150 ml)
o Acts as a fresh gas reservoir during inspiration.
o Capacity more than the expected tidal volume.
o Used in neonates, infants and paediatric patient (<20kg
weight or <5 years).

42. MAPELSON F
o Jackson Rees Modification of Mapleson’s E
o Mapleson’s E + reservoir bag (volume 500ml)
o Reservoir Bag :
• Open tail end/ valve at the tail end
• Monitors spontaneous ventilation
• Assists in controlled ventilation
• Vents out excess gasses
o Used in : Neonates, Infants & Pediatric patients <20kgs
weight or <5 years old.

43. FUNCTIONAL ANALYSIS
o Spontaneous Ventilation:
• Expiratory limb open to atmosphere
• FGF: 2-3 times minute ventilation
o Controlled ventilation:
• Occlude expiratory limb intermittently, allowing
fresh gas to inflate lungs.
• FGF: 2-3 times minute ventilation

44. FUNCTIONAL ANALYSIS
o Inspiration: fresh gas from inlet and from expiratory limb
o Expiration: fresh gas & exhaled gas collect in the bag.
o Expiratory pause: the expired gases replaced by fresh
gas in the expiratory limb.
o Heat and moisture exchanger NOT to be used as it
increases resistance.
o Rebreathing and air dilution
o Air Dilution prevented: volume of expiratory limb > tidal
volume of patient

45. o Advantages:
• Easy to assemble
• Inexpensive.
• Low resistance system due to the absence of valves.
• Light weight.
o Disadvantages:
• High fresh gas flows: Atmospheric pollution.
• No Humidification of gases.
• Barotrauma: overinflation during controlled ventilation.

47. CIRCUIT WITH CO2 ABSORPTION
WATER’S TO & FRO

48. CIRCLE SYSTEM
The Circle system can be either:
o Closed:- Fresh gas inflow exactly equal to patient
uptake, complete rebreathing after carbon dioxide
absorbed, and APL closed.
o Semi-closed :- Some rebreathing occurs, FGF and APL
settings at intermediate values .
o Semi-open :- No rebreathing, high fresh gas flow
[higher than minute ventilation].

49. CIRCLE SYSTEM WITH ABSORBER
Characteristics:
o Circle System – Unidirectional valves separate limb
for inspiration and expiration.
o Low flow of gases - CO2 absorber – minimal to low
flow with retained moisture, heat, economical and
less pollution.
o Monitoring
o Denitrogenation & offloading.

51. o Advantages:
 Conservation of Heat & Humidity
 Cost Effective
 Reduces Atmospheric/OT pollution
o Disadvantages:
 Vigilance
 Extensive monitoring of gases
 Accumulation of by products

52. BREATHING CIRCUIT
o Mapleson’s A Circuit: spontaneous ventilation
o Bain’s Circuit: Universal Circuit
o Closed Circuit: economical & prevents
pollution

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