Breathing circuit in anaesthesia and its uses

breathing circuits are used in anaesthesia and critical care. its usage and understanding is at most important for resident doctors and interns.
also widely used in tranporting intubated patients to the icu operation theater and outside the hospital

1. Dr SS Harsoor
Bangalore

2. With Divine Blessings of Sri Sai Baba

3. Definition
History
Ideal requirements
Components
Classification
Mapelson’s Alphabets A,B, C, D,
Afferent & efferent Reservoir systems
Unidirectional & Bidirectional systems
×Unidirectional Nonrebreathing system

4. Anaesthesia breathing system is defined
as an assembly of components which
connect the patient’s airway to the
anaesthesia gas delivery system, from
and into which the patient breathes.

5. 1931- Waters used “To and Fro” canister
for anaesthesia with cyclopropane.
1936, Brian Sword introduced the circle
system
1937-The Ayre’s T-piece was introduced.
EMO inhaler in 1941
Minnitt’s ‘gas and air’ apparatus in 1949.
1950s- Ivan Magill, “Magill’s circuit”.
1972 – Bain’s System

6. 1950 – Reservoir bag with an open tail, on
Ayre’s T piece.
1976 - Lack system (scavenging)
1998 – Ayre’s T piece with APL valve
The Mapleson C: Bagging system for
resuscitation
Presently : silver ion based anti-microbial
additives to reduce the potential risk of
cross contamination.

7. Essential:
Must deliver gases to the alveoli in the shortest
possible time and in desired concentration
Effectively eliminate carbon-dioxide
Have minimal apparatus dead space & low resistance.
Desirable:
Conserve heat and humidity inspired gases
Economy of fresh gas.
Efficient for both spontaneous & controlled ventilation
Useful for ventilation in all ages & ventilators
Sturdy, small & Light weight & reduce theatre pollution.

8. Fresh Gas connection
Delivery Tubing ( Corrugated)
Reservoir Bag
Adjustable Pressure Limiting (APL) Valve
Patient connection
Waste gas connection ( Pollution)

9. Several classifications suggested
Many appear irrelevant as do not define a
breathing system (added to confusion ?)
McMohan 1951 - Open, Semiclosed &
Closed
Dripps proposed the names Insufflation,
Open, Semiopen, Semiclosed and Closed
Conway suggested a classification based
on use of CO
2 absorber

10. Open method : Dropping
ether or chloroform over
a gauze or lint.
Modernised by the likes
of the Schimmelbusch
mask.
oSemi-closed : Mapleson systems.
oClosed systems use a CO
2 absorbent so that
the gases are re-circulated.

11. Prof. WW Mapleson (1954) from University of
Wales, Cardiff, classified the breathing systems
based on the assembly of components & their
position in the system.
Useful for easy identification ‘The Mapleson
Alphabet’
Miller added his new breathing system called
“The Maxima”
Humphrey ADE system

12. The F was added later to the alphabet

13. For better understanding of the functional
analysis, Mapelson systems are further
classified as :
•Afferent reservoir system (ARS).
•Efferent reservoir systems (ERS).
•Enclosed afferent reservoir systems(EARS)
•Combined systems.

14. The reservoir bag is
placed in afferent
limb of the breathing
system
(which delivers fresh
gas to patient)
AR systems work efficiently during spontaneous
breathing but not during controlled ventilation

15. The reservoir bag is
placed in efferent limb
of breathing system
(which carries expired
gas away from patient )
oWork efficiently & economically for Controlled.
ventilation if FG entry & expiratory valve are
separated by at least Pts one tidal volume.
oNot economical during spontaneous breathing.

16. Afferent Reservoir System

17. From Dr Guy Watney
Sir Ivan Magill, Anaesthetist from London
The original Mapleson A system

18. Sponteneous ventilation
When bag is full, the expiratory valve opens &
the alveolar gas is vented out
During the expiratory pause, expired gas in
the corrugated tube is pushed out
The system functions efficiently, when the FGF
equals the alveolar ventilation ( and the dead
space gas )

19. Controlled Ventilation
Rebreathing
Wastage of Gases

Expiratory valve needs to be partly closed to
generate inspiratory pressure
When sufficient pressure is developed, part of
the expired gas and part of the FG escape
through the valve
Not suitable for Controlled ventilation

20. Dr A Lack Anaesthetist from Salisbury UK
Functions like a Mapleson A system
Efferent tube placed coaxially
The expired gas is vented through valve placed
near the machine end to facilitate scavenging.

21. FG entry shifted near patient end
Aimed to reduce rebreathing and
Improve utilization of FG (during controlled
ventilation)
Neither efficient during spontaneous nor
during controlled ventilation.
Resuscitation
FGF> 15 LPM

22. Similar to Mapleson B
FGF= 2MV required to prevent rebreathing
Water's circuit without an absorber
APL valve added (1998)

23. Efferent Reservoir Systems

24. 6 mm tube acts as the afferent limb
The efferent limb is a wide-bore corrugated
tube (reservoir bag attached)
Expiratory valve is positioned near bag.
In Bain system, (Modified D System)the afferent
& efferent limbs are coaxially placed
Mapleson E, the corrugated tube acts as the
reservoir
All ER systems are modified Ayre’s T-piece

25. Bain JA, & Spoerel WE. London-Ontario Canada
1973
Quest for a system for neurosurgical
anaesthesia & facilitate scavenging of
anaesthetic gases.
Coaxial systems require a Integrity Check

26. Spontaneous respiration
Composition of inspired gas influenced by
FGF,
×Respiratory rate,
×Expiratory pause,
×Tidal volume
×CO
2 production.
FGF should be atleast 1.5 to 2 times MV to
minimise rebreathing

27. Controlled ventilation
During inspiration a mixture of dead space gas,
alveolar gas & FG reach alveoli.
Later the expiratory valve opens and the contents of
the reservoir bag are discharged into the atmosphere
Composition of inspired gas influenced by
FGF,
Respiratory rate,
Expiratory pause,
Tidal volume
×CO
2 production.
•But these parameters can be totally controlled by the
anaesthesiologist

28. Sponteneous Breathing: A high
FGF and a normal minute
volume of 70 ml/kg to achieve
normal PaCO
2 of 40 mm Hg.
Controlled Ventilation: A FGF
equivalent to MV i.e., 70 ml/kg
is chosen and ventilated with at
least twice the predicted minute
volume i.e. 140 ml/Kg
(deliberate controlled
rebreathing)
Relation between alveolar ventilation and FGF

29. Mapleson E is a modified Ayre's T-piece
Developed in 1937 by Phillip Ayre
(A Newcastle anaesthetist) for use in
paediatric patients undergoing cleft
palate repair or intracranial surgery.
Children under 20 kg weight.

30. Light metal tube 1 cm diameter,
5 cm in length
A side arm
Low Resistance
Dead space is minimal
No rebreathing (expired gas is vented into
the atmosphere)
Addition of reservoir will reduce FGF
requirements

31. FGF >2.5 to 3 X MV suggested
As tidal volume is supplied during the
expiratory pause, even a low FGF is
adequate during controlled Ventilation
In practice FGF =1.5 - 2 X MV is adequate

32. BREATHING SYSTEMS WITH CO
2 ABSORPTION

33. Semi-closed systems rely on FGF rate for
effective elimination of CO
2
Circle systems depend on chemical
absorption( Soda lime) for removal of
expired CO
2 .
•Unidirectional : Closed / Circle system
•Bidirectional : Water’s To & Fro system

34. Components of the circle system are,
•Exp relief valve.
•Sodalime canister,
•Two One way valves,
•Fresh gas inlet,
•Y-piece,
•Low resistance tube
•Reservoir bag

35. Components of the circle system are,
•Exp relief valve
•Sodalime canister,
•Two One way valves,
•Fresh gas inlet,
•Y-piece,
•Low resistance tube
•Reservoir bag
Inspiratory
Expiratory

36. Arrangements of components is important
when CO
2 absorber not used
( Very high FGF is needed.)
Unidirectional valves
FGF enters proximal to inspiratory valve.
APL Valve in expiratory limb
Reservoir bag placed in expiratory limb
CO
2 absorption system ( sodalime)
When the FGF is less than Minute volume, the
CO
2 absorber is a must

37. Advantages :
Economy: The FGF can be as low as 250 - 500
ml of O
2 & economy of anaesthetics.
Humidification: Inspired gas fully saturated
with water vapour
Conserves heat: The CO
2 absorption is an
exothermic reaction
Reduction in atmospheric pollution

38. BI-DIRECTIONAL FLOW SYSTEMS

39. Water’s to and fro system
Valveless (APL)
Convenient
Portable
KOH
+
was used
Veterinary practice

40. DisAdv:
Metal body can cause facial burns
Sodalime Dust can be a problem
Increase in dead space
Channeling
Heavy to use

41. Summary

42. Description of system should be
•Semi-Closed or Closed
•Mapleson Alphabet
•Afferent or Efferent reservoir systems
•Unidirectional or Bi-Directional flow
•With or Without CO
2 absorber.
•Co-axial system

43. Thank you