The document discusses different types of breathing systems used in anesthesia, including their components, principles of function, and classifications based on gas flow patterns and carbon dioxide elimination methods. Key systems described include the Mapleson A, B, C, and D circuits as well as the Bain system.

1. DR D. SUVANKAR
SETH G.S.MC and KEM HOSPITAL,MUMBAI

2. A breathing system is defined as an assembly of
components which connects the patient’s airway to
the anaesthesia machine creating an artificial
atmosphere, from and into which the patient
breathes.
Definition

3. Anesthesia Breathing Systems
Basic Principles
• All anesthesia breathing systems have 2 fundamental
purposes
 Delivery of O2/Anesthetic gases
 Elimination of CO2 (either by washout with
adequate fresh gas flow (FGF) or by soda lime
absorption)

4. Essential/ Principle Criteria
The breathing system must
a) Deliver the gases from the machine to the alveoli in the same concentration as
set and in the shortest possible time.
b) Effectively eliminate carbon-dioxide.
c) Have minimal apparatus dead space.
d) Have low resistance.

5. Desirable/Secondary Criteria
The desirable requirements are
a) economy of fresh gas.
b) conservation of heat.
c) adequate humidification of inspired gas.
d) light weight
e) Convenience during use.
f) Efficient during spontaneous as well as controlled ventilation (efficiency is
determined in terms of CO2 elimination and fresh gas utilization)
g) Adaptability for adults, children and
h) mechanical ventilators
i) Provision to reduce theatre polluton
j) Other function gas sampling, pressure and volume monitoring.

6. Components of breathing system:
It primarily consists of
a) A fresh gas entry port/delivery tube through which gases are delivered from
the machine to the systems.
b) A port to connect it to the patients airway.
c) A reservoir bag for a gas in the form of a bag or a tube to meet the peak
inspiratory flow requirements
d) Breathing tubes
e) Adjustable pressure limiting (APL) valve/pop off valve
f) Connectors and adaptors
g) Filters
h) Humidification systems
i) Peep valves ( manual and electronic)

7. RESERVOIR BAGS
Composition Rubber, synthetic latex, neoprene.
Ellipsoidal in shape.
Available in sizes 0.5L to 3L.
A normal size adult bag holds a volume exceeding the patients
inspiratory capacity.

8. RESERVOIR BAGS
Functions :
i. Reservoir
ii. Provides PIF.
iii. It provides a means whereby ventilation may be assisted or controlled.
iv. It protects the patient from excessive pressure in the breathing system.
v. It can serve through visual & tactile observation as a monitor of patients
spontaneous respiration.

9. Breathing Tubes
1. Made of rubber or plastic or silicone.
2. It may be coaxial or side by side.
3. Can be impregnated with silver to add
antimicrobial effect.
4. Length is variable.
5. Internal diameter
 Adults – 22mm.
 Pediatric – 15mm.
6. Internal volume  400-500ml/metre.
7. Distensibility  0-5ml/metre/mmHg

10. Breathing Tubes
7. Resistance to gas flow  <1mm of H₂O/liter/min of flow
8. Corrugations prevent kinking & increased flexibility.
Functions
1. Act as reservoir in certain systems.
2. They provide connection from 1 part of system to another.

11. Breathing Tubes
 Backlash  seen during spontaneous breathing. Breathing
tubes tend to collapse during inspiration and bulge during
expiration. This may cause rebreathing.
 Wasted ventilation  seen during controlled breathing. The
tubes tend to bulge on positive pressure breath (inspiration)
and return to resting position on exhalation. This results in less
volume entering the patient than the one leaving the reservoir
bag or a ventilator

12. Adjustable Pressure Limiting Valve (APL Valve)
Also called as expiratory valve, pressure relief valve, pop off valve,
Heidbrink valve, Dump valve, Exhaust valve, Spill valve.
Ex:- Spring loaded disc and Stem and seat type of valve
Spring Loaded Disc
 Most commonly used type.
Has 3 ports –Inlet,
The Patient &
Exhaust Port.
 Exhaust port may be open to atmosphere or scavenging
system

13. Adjustable Pressure Limiting Valve (APL Valve)
Parts of Spring Loaded Disc
1. Female taper
2. Retaining screw
3. Stem with disc
4. Spring
5. Valve tap

14. Uses of APL valves in spontaneous & controlled
ventilation
Spontaneous
• Valve is kept fully opened.
• Partial closing will result in CPAP.
• Pressure <1cm H₂O needed to open valve.
Controlled
• Valve is partially left open.

15. Classification of Breathing
Systems

16. Classification of Breathing Systems
Dripps et al classified them as Insufflation , open , semiopen , semiclosed and
closed taking into account the presence or absence of
 Reservoir
 Rebreathing
 Co2 absorption
 Directional valves
Collins divided breathing system into four broad groups depending on whether
• the ambient (atmosphere) air is allowed to enter the system -open or
semiopen
• and/or the system allows gases from it to enter the ambient (atmosphere)-
semiopen or semiclosed.

17. Classification of Breathing Systems
Open System–
• Anaesthetic gases are delivered directly into the patient’s airways
• Atmospheric air acts as diluent
• Patient’s airways has access to the atmosphere during both inspiration and expiration
• No reservoir
• No rebreathing
• No neutralization of CO2
• No unidirectional valves
Example
1. Nasal cannula
2. An open ether mask held away from the patient’s face

18. Classification of Breathing Systems
Semi Open System–
• Patient’s respiratory system is open to atmosphere both during inspiration and expiration
through a reservoir that is open to atmosphere
• Atmospheric air either carries or dilutes the anaesthetic agents
• Gas reservoir present
• No rebreathing
• No neutralization of CO2
• No unidirectional valves
• Fresh gas flow exceeds minute ventilation
Examples include
1. Open ether mask held in close proximity to the face
2. ayre's T-piece with no expiratory limb or expiratory limb capacity less than tidal volume of the
patient where air dilution occurs

19. Classification of Breathing Systems
Semi Closed
• Patient’s respiratory system is completely closed to atmosphere on inspiration but partly or fully
open to atmosphere on exhalation
• A reservoir is not open to atmosphere
• Rebreathing may or may not be present
Example
1. Mapleson rebreathing systems
2. Circle absorber with APL valve open allowing venting of gases
3. Water’s to and fro system

20. Classification of Breathing Systems
Closed system
• No access to atmosphere either on inspiration or exhalation
• No escape of anaesthetic agent is allowed
• Rebreathing is complete
• Reservoir is present
• CO2 absorber is present
• unidirectional valve
Example
1. Circle system with APL valve completely closed

21. Classification of Breathing Systems
Conway classified the breathing system functionally according to
method used for CO2 elimination
 Breathing system with CO2 absorber
 Breathing system without CO2 absorber

22. Breathing system without CO₂ absorption Breathing system with CO₂ absorption
Unidirectional flow
1. Non-rebreathing Valve.
Unidirectional Flow
• Circle system with Absorber
Bi Directional Flow
a) Afferent Reservoir Systems
• Mapleson A
• Mapleson B
• Mapleson C
• Lack`s system
b) Enclosed Afferent Reservoir Systems
• Millers (1988)
c) Efferent Reservoir Systems
• Mapleson D
• Mapleson E
• Mapleson F &
• Bain`s system.
d) Combined Systems
• Humphrey ADE
Bi directional flow
•To & Fro System

23. Breathing systems without CO2
absorber
1) Unidirectional flow
• Non Rebreathing System
• They make use of non-rebreathing valves.
• To prevent rebreathing FGF =MV.

24. Non Rebreathing System
These systems are not very popular because
1. Fresh gas flow has to be constantly adjusted and is not economical.
2. There is no humidification of inspired gases.
3. There is no conservation of heat
4. The valve is bulky and has to be placed close to the patient.
5. Malfunctioning of the valve can occur due to condensation of moisture.
6. Can be noisy at times.
7. Cleaning and sterilization is somewhat difficult

25. Bi Directional Flow without CO2 absorption
For better understanding of functional analysis they have been
classified as
1)Afferent Reservoir System (ARS)
2) Enclosed Afferent Reservoir System
3) Efferent Reservoir System
4) Combined System
The efficiency of a system is determined in terms of CO₂
elimination & FGF utilization.

26. Bi Directional Flow without CO2 absorption
• Afferent limb is that part of the breathing system which delivers
the fresh gas from the machine to the patient.
• If the reservoir is placed in this limb as in Mapleson A, B, C and
Lack’s systems they are called as afferent reservoir system.
• Efferent limb is that part of the breathing system which carries the
expired gas from the patient and vents it to the atmosphere through
the expiratory valve/port.
• If the reservoir is placed in this limb as in Mapleson D, E, F and Bain
systems they are called efferent reservoir system

27. MAPLESON BREATHING SYSTEM
• In 1954 –Mapleson collected the
existing breathing systems;
analyzed and classified the
Breathing systems.

28. Mapleson postulates (1954)
Mapleson had analyzed these bi-directional flow
systems & few basic assumptions have been made
which are of historical interest.
• Gases move En-bloc i.e. they maintain their identity
as fresh gas, dead space gas & alveolar gas. There is
no mixing of these gases.
• Reservoir bags continues to fill up, without offering
any resistance till it is full.

29. • The expiratory valve opens as soon as the reservoir
bag is full & pressure inside the system goes above
the atmospheric pressure.
• The valve remains open throughout the expiratory
phase without offering any resistance to gas flow &
closes at the start of next inspiration.

30. Mapleson A (Magill‘s) System

31. 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.

32. Mapleson A (Magill‘s) System
• It consist of a three-way T-tube connected to the fresh gas outlet, a
reservoir bag and a corrugated tube.
• The other end of the reservoir tube is connected to the patient and a
spring-loaded APL valve.
• Corrugated rubber or plastic tubing: 110-130 cm in length.
• Reservoir Bag at Machine end.
• APL valve at the patient end.

33. Functional Analysis : Spontaneous
FGF Dead space gas Alveolar gas

34. Functional Analysis : Spontaneous
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
FGF is :-
High –Force the dead space gas out.
Intermediate –Some dead space gas will be retained in the system.
Low –More alveolar gas will be retained.

35. Controlled Ventilation:
First Breath
Exhalation
Next Inspiration

36. Mapleson A (Magill‘s) System
Advantages
• Best among all Mapleson’s 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 (Heidbrink valve).
• Expiratory valve is near patient and inconvenient to use.
• Not suitable for paediatric use.

37. 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.

38. Mapleson A – Lack Modification
• 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.

39. Mapleson A – Lack Modification
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.

40. TESTING FOR LEAKS/MAGILL
A) To attach a tracheal tube to the inner tubing at the patient
end of the system. Blowing down the tube with the APL
Valve closed will produce movement of the bag, if there is a
leak between the two limbs.
B) To occlude both limbs at the patient connection with the
APL Valve open & then squeeze the bag. Leak in the inner
limb, gas will escape through the APL Valve & the bag will
collapse.

41. Enclosed Afferent Reservoir
Systems

42. Enclosed Afferent Reservoir (EAR) Systems
• Coaxial version
• Non coaxial version

43. Enclosed Afferent Reservoir (EAR) Systems
• The Enclosed Afferent Reservoir (EAR) is described by Miller.
• It consists of Mapleson A system enclosed within a non distensible
structure
• It is also constructed by enclosing the reservoir bag alone in a bottle
and connecting the expiratory port to the bottle with a corrugated tube
and a one-way valve.
• To the bottle is also attached a reservoir bag and a variable orifice for
providing positive pressure ventilation

44. Enclosed Afferent Reservoir (EAR) Systems
ADVANTAGES
1. This system provides selective elimination of alveolar gas in
both spontaneous and controlled ventilation
2. A comparison with Bain’s circuit in controlled ventilation
demonstrated greater efficiency in eliminating CO2. A FGF of
70ml/kg/min using EAR system gave minimal hypocarbia which
equated to a FGF of 100ml/kg/min using a Bain’s system.
3. More efficient than Bain for controlled ventilation.

45. MAPLESON B SYSTEM

46. MAPLESON B SYSTEM

47. 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.

48. MAPLESON C SYSTEM

49. MAPLESON C SYSTEM

50. MAPLESON C SYSTEM
• This circuit is also known as Water’s circuit.
• This circuit is sometimes used in portable ventilators.
• It is similar in construction to the Mapleson B , but the main tube is
shorter.
• A FGF equal to twice the to 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.

51. MAPLESON D SYSTEM

52. 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

53. Bain system (Mapleson D)

54. Bain system (Mapleson D)
• 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

55. Bain system (Mapleson D)
Specifications:-
• Length-1.8 meters.
• Diameter of outer tube-22mm(transparent, carries expiratory gases)
• Diameter of inner tubing-7 mm(inspiratory)
• Resistance-Less than 0.7 cm H2O
• Dead space-Outer tube upto expiratory valve( around 500ml=TV)
• Flow settings- For controlled ventilation
< 10kg 2L/min
10-50 kg 3.5L/min
>60kg 70ml/kg
For spontaneous ventilation
200-300ml/kg

56. Bain system (Mapleson D)- Functional Analysis

57. 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.

58. Bain system (Mapleson D)- Functional Analysis
controlled

59. Bain system (Mapleson D)- Functional Analysis
• 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.

60. Bain system (Mapleson D)
Factors governing concentration of Inspired Mixture in Mapleson D system
• FGF rate
• Respiratory rate
• Expiratory pause
• Tidal volume

61. Bain system (Mapleson D)
• In spontaneous breathing only FGF can be manipulated. Hence it has to
be 2 to 4 times the patient’s minute ventilation(200 -300ml/kg) to
minimize rebreathing of exhaled alveolar gases.
• In controlled breathing, these factors can be totally manipulated. So
using low respiratory rate, long expiratory pause and high tidal volume
most of the fresh gas(70ml/kg) could be used for alveolar ventilation
without wastage.

62. 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 assist and controlled ventilation .
• 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 and humidification of the inspired fresh gas by the exhaled gas
present in outer tubing.

63. 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 inner tube blocking the fresh gas supply leading to hypoxia
• There can be crack in the inner tube causing leakage
• It cannot be used in paediatric patients with weight less than 20 kg.

64. Checking the Bain’s circuit
1)Pethicks test - To check the integrity of the inner tube
• Flush high flow into the circuit and occlude the patient end until the reservoir bag
is filled
• The patient end is then opened and circuit is then flushed with oxygen
• If inner tubing is intact, the venturi effect occurs at the patient end, causing
decrease in pressure within the circuit and bag will deflate
• If there is leak in inner tubing, fresh gas will escape in the expiratory limb and the
bag will inflate

65. Checking the Bain’s circuit
• For checking integrity of inner tube of Bain’s system, a test is performed by
setting a low flow on the oxygen flowmeter and occluding the inner tube
with a finger or barrel of a small syringe at the patient end while observing
the flow meter indicator. If the inner tube is intact and correctly connected,
the indicator will fall due to back pressure.
• Integrity of APL valve and scavenging system: By occluding the patient end
and closing the APL valve the system is pressurized. The APL valve is then
opened. The bag should deflate easily if the valve is working properly.
• Integrity of outer tubing:Wet the hands with spirit. Blow air through the
tube. Wipe the tube with wet hands. Leak will produce chillness in the
hands.

66. Mapleson E
OR
Ayre's T- PIECE

67. Mapleson E OR ayre's T- PIECE

68. Mapleson E OR ayre's T- PIECE
• Introduced by Phillips Arye in 1937.
• Belongs to Mapleson E.
• Available as metallic / plastic.
• Length-5cm and Diameter-1cm.
• Parts – inlet, outlet, side tube.

69. Mapleson E OR ayre's T- PIECE
• Fresh gas enters the system through the side arm
• One end of the body is connected to the patient(apparatus dead
space) and the other end is connected to the tubing which acts as
reservoir
• This system is suited in neonates and infants in whom expiratory
valve would produce significant resistance

70. Mapleson E OR ayre's T- PIECE
Spontaneous breathing
Inspiration:
 Since the peak inspiratory flow rates are higher than FGF, gases are
dawn from the reservoir limb.
 If the reservoir limb capacity is less than the tidal volume of the
patient then air dilution occurs, converting the semiclosed system
into semiopen system as per Collin’s classification.

71. Mapleson E OR ayre's T- PIECE
Exhalation:
 Both exhaled and FGF pass into the reservoir limb and then to the atmosphere.
End Expiratory Pause:
 FGF flushes out and fills the reservoir limb with fresh gases pushing out the
exhaled gases.
 If the reservoir limb capacity is more than the tidal volume of the patient and
FGF are less than rebreathing occurs

72. Harrison modification of ayre's T- PIECE
Harrison reviewed modifications of T-piece in relation to the capacity of the
reservoir(expiratory limb) and classified T-piece system into 3 categories
 Type I – No expiratory limb
 Type II – Volume of expiratory limb greater than the patient’s tidal volume
 Type III - Volume of expiratory limb lesser than the patient’s tidal volume
He concluded that the most useful was Type II

73. Mapleson E OR ayre's T- PIECE
Factors to be considered for Spontaneous Breathing
• Diameter of reservoir must be sufficient to have lowest possible resistance.
• Volume of reservoir limb(RV) should not be less than the patient’s tidal volume(TV)
• If RV=TV , then FGF=2.5 times minute ventilation is required to prevent air dilution
• If RV is less than TV, then FGF has to be increased further, otherwise air dilution can occur
• If RV=0 (no expiratory limb) than TV, then FGF should be atleast equal to the peak
inspiratory flow rate of the patient to prevent air dilution

74. Mapleson E OR ayre's T- PIECE
WORKING : Controlled Ventilation
• It is done by intermittently occluding the reservoir limb by thumb.
• Neither air dilution nor rebreathing can ever occur.

75. Mapleson E OR ayre's T- PIECE
WORKING : Controlled Ventilation
ADVANTAGES
• Low resistance
• Low dead space
• No valves so easy to use
DISDADVANTAGES
• Barotrauma
• No feel of the bag
• No APL valve so no pressure buffering effect of the bag
• Difficult to scavenge

76. Mapleson F
OR
Jackson-Rees Modification
of Ayre's T- PIECE

77. Mapleson F OR Jackson-Rees Modification of ayre's
T- PIECE
• 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.

78. Mapleson F OR Jackson-Rees
Modification of ayre's T- PIECE

79. Mapleson F Breathing System
Technique of use
• It also functions like Mapleson D system.
• The flows required to prevent rebreathing are 2 - 3 times minute
volume during spontaneous ventilation.
• The flows required to prevent rebreathing are 1000 + 100ml/kg
during controlled ventilation.

80. Mapleson F Breathing System
For spontaneous respiration:
 The relief mechanism of the bag is left fully open. The pattern and rate of
breathing
Small movements of the bag demonstrate the pattern and rate of breathing.
For controlled respiration:
Inspiration:
 The hole in the bag can be occluded partially or completely by the user during
inspiration and ventilation is done by squeezing the bag.
Expiration:
 The open end is released to allow the gas in the system to escape

81. Mapleson F Breathing System
ADVANTAGES
1. Simple and easy to assemble
2. Light weight
3. Portable
4. No valves
5. Least resistance
6. Suitable for paediatric patients
7. Inexpensive
8. Effective for both controlled and spontaneous ventilation

82. Mapleson F Breathing System
DISADVANTAGES
1. Wastage of gases
2. It lacks humidification
3. Barotrauma – occlusion of relief valve can increase airway pressure producing
barotrauma

83. BREATHING SYSTEM
( MAPLESON)
SPONTANEOUS CONTROLLED
A 1.5 – 2 x M.V 2-5 x M.V
D 2 - 4 x M.V 70ml/kg/min
F 2 - 3 x M.V 1000ml + 100ml/kg/min
TO PREVENT REBREATHING IN THE BREATHING UNIT

84. Combined System
HUMPHREY A D E System

85. Combined System
• Humphry ADE: with two reservoirs one in afferent
and one in efferent limb
• System can be changed from ARS to ERS by
changing the position of the lever.
• Can be used for adults and children.

86. Combined System

87. Humphrey ADE Circuit 1

88. Humphrey ADE Circuit 2

89. Breathing Systems with
CO2 Absorption

90. Breathing Systems with CO2 Absorption
Components of Circle System
1. Fresh gas entry,
2. Two unidirectional valves,
3. Sodalime canister
4. Y-piece to connect to the patient,
5. Reservoir bag
6. A relief valve and
7. Low resistance interconnecting tubing.

91. Breathing Systems with CO2 Absorption
• The FGF should enter the system proximal to the
inspiratory unidirectional valve.
• There should be two unidirectional valves on
either side of the reservoir bag and the canister,
• Relief valve should be positioned in the expiratory
limb only,
3 Essential Factors

92. Breathing Systems with CO2 Absorption

93. • Let us start adding parts to our circle, in a step by step way..
• A circle is added to the patient.

94.  However, though we have connected the patient to the circle, he will
unfortunately not be able to breath in or out from it. This is because the
circular tube is made of a non stretchable material and therefore it cannot
expand to accept the patient's expiration, and nor can it contract when the
patient tries to inspire from it.

95. To allow the patient to breath in and out, we attach a flexible bag (
called reservoir bag ) to the circle system. Now the patient can
breath, through the tubes, into and out of the flexible reservoir bag.

96.  However, if we leave our patient like this, he will not survive, since we are
forgetting to give him something vital for life. We need to urgently give our
patient oxygen !
 The oxygen (and other gases) come out of the flow meters of your anaesthetic
machine. The flow meters allow you to control the flow of the various gases
that you supply to your patient. The total flow of gases coming out of the flow
meters is called " total fresh gas flow" or more commonly , simply referred to
as, "fresh gas flow".

97. So, to keep our patient alive, we supply fresh gas flow ( containing
oxygen, shown as blue dots ) from the flow meters into the circle
system

100.  We " force " the patient to inspire from one part of the circle, and expire into the other part of the
circle, using what are called “one way valves”. As their name suggests, these valves allow gas to pass
one way, and not the other way. The valve has a disc that opens only in one direction, allowing gases
to only go in that direction. In the example below, the one way valve is designed to allow flow in the
direction of the green arrow and not allow flow to go in the opposite direction..
 We add two one way valves into the circle system as shown below. One allows flow only towards the
patient and the other allows flow only away from the patient.

101.  During inspiration, the valve labeled " expiratory one way valve " closes, preventing the
patient from inspiring the gases he just breathed out. On the other side, the valve
labeled " inspiratory one way valve opens, letting the patient inspire gases rich with
oxygen. The tubing from the inspiratory one way valve to the patient carries only
inspiratory gases, and we can therefore call it the “inspiratory tubing”.

102.  During expiration, the reverse happens. The inspiratory one way valve closes,
preventing the expired gases going into the inspiratory tubing. Instead, the valve
labeled "expiratory one way valve" opens, letting expired gases go via the tubing
between it and the patient. The tubing between the patient and the expiratory one
way valve carries only expired gases, so we can therefore call it the “expiratory
tubing”.

103.  However, we discover another problem. We find that the reservoir bag is
mysteriously getting bigger and bigger.
 Ultimately the reservoir bag will burst.

105.  It would not be very pleasant to have reservoir bags bursting every few
minutes, so we need a solution. The answer is to add an “pressure
limiting outflow valve” to the circle. This valve has a disc that is
designed to open when a positive pressure develops on one side of it,
thereby letting any excess gas to flow out and prevent further rises of
pressure.

106. During inspiration, the pressure in the system is low, so the pressure limiting
outflow valve remains closed.

107.  Now our patients breathes out. During early expiration, the expired gases go into
the reservoir bag. Because the pressure is low, the pressure limiting outflow valve
remains closed.

108. The expiratory gases fill the reservoir bag till it is fully distended. Once the bag is fully
distended, the expired gases have nowhere to go and the pressure in the circle system
rises.
 The rise in pressure causes the pressure limiting outflow valve to open, releasing the
excess gases (grey arrow ) out of the circle system. In this way, the pressure limiting
outflow valve lets excess gas escape and prevents a rise in the circle system pressure.

109.  Now that our patient can inspire and expire nicely. we can ask the question; “Is he
happy ?” The answer unfortunately is “No”. The reason the patient is not happy is
that he is inspiring his own carbon dioxide ( shown as grey dots ).

110. Let us include a CO2 absorber into our circle system. Now as the patient inspires,
the CO2 containing gas from the reservoir bag passes through the CO2 absorber.
The absorber "absorbs" the CO2, making the inspired gas CO2 free

111.  You need to give the patient anaesthetic gases to keep him asleep. We do this by
adding anaesthetic vapours (yellow dots ) to the fresh gas flow using a vaporizer.

112. Optimization of Circle Design
• Unidirectional Valves
• Close to patient to prevent backflow into inspiratory limb if circuit leak
develops.
• Fresh Gas Inlet
• Placed between absorber & inspiratory valve. If placed downstream from
inspiratory valve, it would allow FG to bypass patient during exhalation and be
wasted. FG placed between expiration valve and absorber would be diluted by
recirculating gas

113. Optimization of Circle Design
APL valve
• Placed immediately before absorber to conserve absorption
capacity and to minimize venting of FG
Breathing Bag
• Placed in expiratory limb to decrease resistance to exhalation. Bag
compression during controlled ventilation will vent alveolar gas
thru APL valve, conserving absorbent

114. Circle system can be:
• closed (fresh gas inflow exactly equal to patient uptake,
complete rebreathing after carbon dioxide absorbed, and pop-
off closed)
• semi-closed (some rebreathing occurs, FGF and pop-off
settings at intermediate values), or
• semi-open (no rebreathing, high fresh gas flow)

115. Anesthesia Breathing Systems
• Circle systems
– Most commonly used
– Adult and child appropriate sizes
– Uses chemical neutralization of CO2
– Conservation of moisture and body heat
– Allows for mechanical ventilation of the lungs using the attached
ventilator
– Allows for adjustment of ventilatory pressure
– Is easily scavenged to avoid pollution of OR environment
– Low FGF’s saves money

116. Anesthesia Breathing Systems
• Advantages of rebreathing
– Cost reduction (use less agent and O2)
– Increased tracheal warmth and humidity
– Decreased exposure of OR personnel to waste gases
– Decreased pollution of the environment

117. Disadvantages of Circle System
• Greater size, less portability
• Increased complexity
– Higher risk of disconnection or malfunction.
• Difficulty of predicting inspired gas concentration during low fresh gas flow

118. WATER’S TO AND FRO
ABSORPTION SYSTEM

119. WATER’S TO AND FRO ABSORPTION
SYSTEM

120. WATER’S TO AND FRO ABSORPTION
SYSTEM

121. WATER’S TO AND FRO ABSORPTION
SYSTEM
 The patient breathes to and fro from a reservoir bag, which is
connected to the facemask or endotracheal tube via canister soda
lime.
 The system used is Mapleson C system with placement of sodalime
canister between the reservoir bag and FGF port.
 The Fresh gases are introduced at the patient end of the system.
 Exhaled carbon dioxide is absorbed by the soda lime.
 Excess gas is vented when necessary via the APL valve.

122. WATER’S TO AND FRO ABSORPTION
SYSTEMADVANTAGES
1. Inexpensive
2. Portable
3. Economy with low flow of oxygen, nitrous and volatile agents
4. Reduction of operating room pollution
5. Conservation of heat and humidity

123. WATER’S TO AND FRO ABSORPTION
SYSTEMDISADVANTAGES
1. Cumbersome
2. The soda lime near the patient end become more rapidly exhausted
, leading in insufficiency in soda lime use and a progressive increase
in apparatus dead space.
3. Channeling of gas can lead to rebreathing of gases
4. Expiratory valve position near the patient end is a major
inconvenience
5. Risk of pt. inhaling sodalime.
6. Danger of extubation bcz of weight and proximity to the pt.

124. THANK
YOU