Breathing circuits and circle system for a anesthesized patient

It includes the breathing circuits used for ventilation of patients during surgery

1. Breathing Circuits and
Circle System
PRESENTER: DR.AYESHA
TUTOR :DR MUAZZAM BUTT
UKSO: PROF. DR. MUDASSAR ASLAM

2. Definition
Breathing system is defined as an assembly of components which
connects a patient’s airway to an anaesthesia machine, creating an
artificial atmosphere from and into which the patient breathes.
Basic principles:
1. Delivery of O2
2. Removal of Co2 from patient
3. Delivery of inhaled anaesthetic agents and their elimination from lungs.

3. Properties of Ideal Breathing System
1. Simple and safe to use
2. It should effectively deliver the inhaled gas mixture to the
patient and ensure the easy removal of waste gases on a short
period of time.
3. Have minimal appropriate dead space ( To decrease the
work of breathing )
4. Have low resistance ( e.gWider tubes, shorter lengths and
fewer valves )
Rhetorical
Question
what is a
dead space.

4. CLASSIFICATION
1.Collins classification of breathing Circuit
(Old classification )
 Breathing circuits are broadly classified into 4 groups depending on the
physiological characteristic of rebreathing by the patient.
1. Open
2. Semi-open
3. Semi-closed
4. Closed

5. Classification
Type of
circuits Open Semi-Open Semi-closed Closed
Charact
eristics
Rebreath
ing
No Rebreathing No rebreathing Partial Rebreathing
Complete
Rebreathing
Examples
1.Nasal Cannula
2.Insufflation
1.Open drop
anaesthesia
2.Ayre’s T piece
1.Mapleson circuits
2.Water to and fro
system
1.Circle system
with Apl valve
1.Use atmospheric
fresh gas flow
2. No reservoir
3.No unidirectional
valve
1.Use atmospheric plus
other sources as FGF
2.Gas reservoir present.
3.No unidirectional
valve
1.Completely closed
system on inspiration but
may expose to
atmosphere on
expiration.
2.Reservoir bag is present.
3.Valve is present
1.No access to
atmosphere.
2.Reservoir
bag present.
3.Co2
absorber.

6. 1. Insufflation
Direct blowing of anaesthetic gases across a patient’s face.
It is not categorized as a breathing circuit and is better considered as a
technique.
Commonly used in inductions with inhalational anaesthetics in children.
Disadvantages:
1.High flow rate ( >10L/min) is required
 to avoid rebreathing of exhaled gases.
2.Ventilation is not under control.

7. Open drop Anaesthesia.
In Open drop anaesthesia, a highly
volatile anaesthetic mixture is poured on a
gauze-covered mask ( schimmelbusch
mask ) and applied to patient’s
face.Patient’s breathing converts the
anaesthetic agent into vapours and
carries the high concentration
anaesthetic agent to the patient.
Vaporization lowers mask temperature
and which decreases vapour pressure.
(vapour pressure is proportional to
temperature )

8. Draw over Anaesthesia.
Draw-over anaesthesia isa method of anaesthesia that uses a vaporizer to
add anaesthetic to air without requiring compressed gas.
The patient breathes in through a non-rebreathing valve
Air passes through a vaporizer, where anaesthetic is added
The patient inhales the anaesthetic-rich air
Benefits:Portable, Low cost, Easy to maintain, and Doesn't require
compressed gas.
Drawbacks:
1.Flow through the vaporizer varies based on the patient's breathing rate,
age, and depth of anaesthesia.
2.The flow is intermittent, stopping during exhalation
Application: It is widely used in military and disaster areas.

9. Mapleson Circuits
Components of Mapleson
Circuits:
1.Breathing tubes ( large
diameter of 22mm , low
resistance )
2.Fresh gas inlet
3.Adjustable pressure limiting
valve
4. Reservoir bag
Q. Why breathing tubes’
volume should be equal to
or greater than tidal
volume ?

10. Mapleson Circuit ( Type A )
It is the most widely used mapleson circuit.
It requires FGF flow rate of 70ml/kg/min to
excrete CO2 in spontaneous ventilation.
Components
1. Corrugated rubber or plastic tubing (usually 110–
180cm in length) and an internal volume of at least
550mL.
2. A reservoir bag, mounted at the machine end.
3. APL valve situated at the patient end.
Q. What is the
normal minute
ventilation ?
Q. Why FGF is
required in
high quantity
to excrete
CO2 ?

11. Magill circuit ( Mapleson A )
When the patient inhales, the valve closes and the patient breathes
from the reservoir tube
When the patient exhales, they exhale into the reservoir tube
The bag fills with exhaled gas, and positive pressure opens the valve
to let the gas out.
Advantages:
Efficient for spontaneous ventilation , FGF required is equal to
minute volume.
Disadvantages:
Not useful for controlled ventilation and in paediatrics practice.
Application: It is used in emergency airway management, transport
ventilation, preoxygenation before intubation and short surgical
procedures.

12. Lack breathing system ( Coaxial
Mapleson A )
1.It is the coaxial modification of Magill circuit A.
2. 1.8-m length coaxial tubing (tube inside a tube).
The
FGF is through the outside tube, and the exhaled
gases
flow through the inside tube.
3. Both Apl valve and reservoir bag are at the
machine end.
Advantages:
The location of valve is more convenient,
permitting intermittent positive pressure
ventilation and scavenging of gases.
Disadvantages:
1. The inner tube can be disconnected or can break
resulting in converting whole circuit into dead space.
Parallel lack system
( Designed to avoid
breakage of an inner tube )
Lack coaxial system

13. Mapleson B and Mapleson C Circuits
The FGF is moved closer to the patient end with the
valve and as the pressure in the circuit increases , valve
opens , it removes the alveolar dead space and fresh
gas.
To avoid rebreathing fresh gas flow rate of twice the
minute ventilation is required in both controlled and
spontaneous ventilation.
Mapleson C is also known as Water Fro system.
It is similar to mapleson B in structure but the tube is
shorter and commonly used in resuscitation and in
portable ventilators.
 Mapleson A and B are inefficient to use in both
spontaneous and controlled ventilation.

14. Mapleson D circuit ( Bain circuit )
It consists of fresh gas inlet near the patient
end and a corrugated tube with APL
valve towards the machine end and a
reservoir bag.
Bain Circuit is the coaxial version of
Mapleson D circuit and uses an inner
tubing of 1.8m to deliver fresh gas to the
patient, exhaled gases move through the
outer tubing.
Bain Circuit

15. Bain Coaxial Modification
*Fresh gas delivered to
the patient
*High FGF pushes alveolar
gas and dead space
towards APL valve
*When Circuit pressure
Increases above the
atmospheric P , valve opens

16. Bain Circuit
Advantages:
A.Low dead space.
B.Low resistance to breathing.
C.Good scavenging of waste gases.
D.Partial warming of inspiratory gases
Disadvantages:
A.High fresh gas flow requirements
B.Inner tube may dislodge ,turning whole circuit into dead space.
Application :
Widely used in controlled and assisted ventilation requiring less Fresh gas flow in controlled
ventilation as compared to other mapleson circuits.

17. Tests to check Bain Circuit
The Pethick’s Test for the Bain Circuit:
1. Occlude the patient's end of the circuit (at the elbow)
2. Close the APL valve.
3. Fill the circuit, using the oxygen flush valve.
4. Release the occlusion at the elbow and flush. A Venturi effect flattens the reservoir bag if the inner tube is
patent.
Bain occlusion test:
1. Close the APL valve.
2. Occlude the patient end with a thumb or a cap.
3. Inflate the reservoir bag using oxygen flush.
4. Observe the bag
 A. If the bag remains inflated, the circuit is intact with no occlusion
 B. If the bag deflates rapidly, there may be a leak.

18. Ayre’s T piece ( Open )
The Ayre T-piece is a simple, lightweight, open breathing system used mainly in neonatal and pediatric anesthesia.
It is of a T shape with 3 ports , one for the fresh gas , other port is to patient’s mask or tracheal tube , 3
rd
port is to the
reservoir tubing ( It has no reservoir bag and APL valve )
Advantages :
1. Low Resistance and Minimal Dead Space (Crucial for neonates as they have minimal tidal volume )
2. Effective for Spontaneous Ventilation.
Disadvantages :
1. Requires High FGF during spontaneous ventilation , not effective for controlled ventilation.
2. Scavenging is difficult.
3. Cannot be used for adults.
Application :
Highly used for neonatal and paediatrics anaesthesia.

19. Jackson-Rees’ Modification
(Mapleson F )
Mapleson E with a breathing bag connected to
the end of the breathing tube to allow controlled
ventilation and scavenging is termed as mapleson
F or Jackson Rees modification.
Application:
Paediatrics Anesthesia
APL
Valve

21. Circle System
The circle system is a closed-circuit breathing system used in anesthesia that
recycles exhaled gases after removing carbon dioxide, allowing efficient use of
anaesthetic agents and oxygen.
Components:
1. A Co2 absorber containing CO2 absorbent.
2. A fresh gas Inlet.
3. Inspiratory unidirectional valve and inspiratory breathing tube.
4. A Y- Connector.
5. Expiratory unidirectional valve and expiratory breathing tube.
6. APL valve.
7. Reservoir Bag.

22. A Circle System

23. Optimization Of circuit Design
1. Unidirectional valve is placed relatively close to the patient to
prevent backflow if circuit leak develops.
2. Fresh gas inlet is positioned between the absorber and inspiratory
valve and is downstream from the inspiratory valve ( Only entry into
the inspiratory limb , high conc oxygen and inhaled anaesthetics
reach to the patient )
3. Apl valve is positioned close to reservoir bag and distal to
expiratory valve. APL valve is functioned to remove waste gases from
expiratory limb of circuit into the gas scavenger system. Its position
before expiratory valve and distal to absorber will remove
anaesthetic agent from the circuit.
4. Resistance to exhalation is reduced by placing reservoir bag in
expiratory limb.
Q. Are anaesthetic
agents reused in circle
system ?
Q. What would happen if
fresh gas is introduced
between absorber and
expiratory limb ?

24. A. Carbon dioxide Absorber
Rebreathing alveolar gases conserve heat and humidity
,however Co2 must be eliminated to prevent hypercapnia.
Soda lime ( Co2 absorbent )
It has the capacity if absorbing 23L of CO2 per 100g of
absorbent.
It uses calcium hydroxide (80%) , along with sodium
hydroxide, water ( 14-19% ) and small amount of potassium
hydroxide.
A Ph indicator dye ( e.g ethyl violet ) changes color from
white to purple.
Silica increases the hardness of Sodalime, it prevents
A. The risk of inhalation of sodium hydroxide
B. Decreases the resistance to gas flow
It is replaced when 50-70% colour is
changed.

25. Co2 Absorber
Granules :
Larger granules offer low resistance and Smaller granules offers higher
absorptive area.
SIZE : 4-8 mesh (number of holes per square of inch of a screen )
The selection of mesh size (and thus granule size) is a balance between
maximizing CO₂ absorption (favouring smaller granules for increased surface
area) and ensuring low resistance to gas flow through the absorber.
Side Effects :
1.Hydroxide salts are irritating to the mucous membrane ( inhalation
prevented by adding silica.
2.Drier the soda lime , the more likely it will absorb and degrade volatile
anaesthetics.
3.Compound A is the degradation product of Sevoflurane by absorbent , it
causes nephrotoxicity.
4.Carbon monoxide formation is greater with Desflurane.
+-----+-----+-----+-----+-----+
| o | o | o | o | o | o |
+-----+-----+-----+-----+-----+
| o | o | o | o | o | o |
+---+-----+-----+-----+-----+
| o | o | o | o | o | o |
+-----+-----+-----+-----+-----+
| o | o | o | o | o | o |
+-----+-----+-----+-----+-----+
➢Greater Mesh size permits larger
granules which have less surface
area and less absorption of gas.

26. B. Unidirectional Valve
Unidirectional valves , which function as check valves,
contains ceramic or mica disc.
Forward flow displaces the disc upward permitting the
gas through the circuit.
Valve incompetence
*Expiratory valve is exposed to humidity of alveolar gases.
*Condensation and resultant moisture formation may
impair upward displacement of disc resulting in
rebreathing.

27. C. Reservoir Bags
Reservoir bags function as a reservoir of anaesthetic gas and a method
of positive pressure ventilation.
Three distinctive phases of reservoir bag filling are recognisable.
1.Adult capacity of Reservoir bag 3-L (Phase-I)
2.After achieving Phase 1, pressure rises rapidly to the peak (Phase-II)
3.Further increases in volume result in a plateau or even a slight decrease in
pressure (Phase III).
Mechanism :
When grossly overinflated, the rubber reservoir bag can limit the pressure in
the breathing system to about 40cm H2O. This is due to Laplace’s law
dictating that the pressure (P) will fall as the bag’s radius (r) increases:
P=2(tension)/r.
Application:
A.Limit pressure build up in breathing system
B.Assist ventilation
C.Accommodates FGF

28. Resuscitation Breathing System
( Laerdal Resuscitator )
AMBU ( artificial manual Breathing unit )
Characteristics :
1.Simple to use
2.Portable
3.Ability to deliver 100% oxygen in emergency ventilation.
4.It has a nonrebreathing valves
A.Patient valve ( allow gas flow from ventilation bag to the patient ), it has a exhalation port which removes gases to the atmosphere and
prevent rebreathing.
B.Intake valve (self inflating bag when compressed , the valve closes , allowing PPV. Bag is filled through fresh gas flow attached through
nipple near the intake valve.
C.Reservoir valve (Reservoir assembly is attached to the unit in case gas flow is inadequate it allows ,through its inlet and outlet valves, the
atmospheric air to enter into ventilation bag.
 Limitations:
1.It requires High Fresh Gas flow to achieve high Fio2
2.Local contamination of atmosphere with no scavenging.
3.Valve can offer resistance to flow due to exhaled moisture.

29. AMBU unit

30. Thank You!