Breathing circuit's

1. Dr:- imran PAEDIATRIC BREATHING CIRCUIT’s

2. DEFINITION: Assembly of components which connects the patient’s airway to the anaesthetic machine creating an artificial atmosphere, from and into which the patient breathes . A breathing system converts continuous flow from the machine to a intermittent flow.

3. INTRODUCTION Any resemblance to a breathing system was developed by Barth (1907) The Mapleson A (Magill) system was designed by Sir Ivan Magill in the 1930's In 1926 , Brian Sword introduced the circle system Ayre’s T-piece was introduced in 1937 Bain Circuit was introduced in 1972 by Bain and Spoerel.

4. CRITERIA FOR IDEAL SYSTEM ESSENTIAL:- 1.Delivery of gas from machine to the alveoli in same concentration as set and in shortest possible time 2.Effective elimination of CO2 3.Minimal dead space 4.Minimal resistance

5. DESIRABLE:- 1.Economy of fresh gas 2.Conservation of heat 3. Adequate humidification 4. Efficient during spontaneous and controlled ventilation 5. Efficient for adult, pediatrics and with mechanical ventilators 6. Light weight 7. Less theater pollution 8. Convenient during use.

6. COMPONENTS 1.Bushings(mount) 2.Sleeves 3.Connectors & Adaptors 4.FGF inlet 5.Breathing tube 6.Reservoir Bag 7.Valve’s 8.Filters 9.CO2 absorber

7. CLASSIFICATION OF BREATHING SYSTEMS McMohan in 1951 Open - no rebreathing Semiclosed - partial rebreathing Closed - total rebreathing Dripps et al have classified them as Insufflation , Open, Semi-open , Semi-closed and Closed

8. Conway suggested a functional classification Breathing systems with CO2 absorber Breathing systems without CO2 absorber.

9. BREATHING SYSTEMS WITHOUT CO2 ABSORPTION BREATHING SYSTEMS WITH CO2 ABSORPTION Unidirectional flow A) Non rebreathing systems. B) Circle systems. Unidirectional flow Circle system with absorber.

10. BREATHING SYSTEMS WITHOUT CO2 ABSORPTION BREATHING SYSTEMS WITH CO2 ABSORPTION Bi-directional flow A) Afferent reservoir systems. - Mapleson A,B,C - Lack’s system. B) Enclosed afferent reservoir systems Miller’s (1988) Bi-directional flow To and Fro system.

11. BREATHING SYSTEMS WITHOUT CO2 ABSORPTION c) Efferent reservoir systems Mapleson D Mapleson E Mapleson F Bain’s system d) Combined systems Humphrey ADE Multi circuit system

12. NONREBREATHING SYSTEM ( Uni -directional) Uses non- rebreathing valve No mixing of fresh gas and expired gas Fresh gas flow =/> Minute volume

13. Disadvantage: ● FGF has to be constantly adjusted so uneconomical ● No humidification ● No conservation of heat ● Not convenient because of bulk of valve ● Valve malfunctioning due to condensation of moisture

14. Bi-Directional Flow system extensively used depend on the FGF for effective elimination of CO2 FGF - No FGF - suffocated - Low FGF - does not eliminate CO2 - High FGF – wastage FGF should be delivered as near the patient’s airway as possible.

15. Mapleson systems 1954 by Professor W W Mapleson - Maplesons A-( magills ) Maplesons B Maplesons C Maplesons D Maplesons E (T-piece) Maplesons F (Jackson-Rees modification of the T-piece)

16. MAPLESON SYSTEM

17. Functional classification Afferent reservoir system ( ARS ). Enclosed afferent reservoir systems ( EARS ). Efferent reservoir systems ( ERS ). Combined systems. Enclosed afferent reservoir system has been described by Miller and Miller.

18. afferent limb - delivers the fresh gas from the machine to the patient. efferent limb - expired gas from the patient and vents it to the atmosphere through the expiratory valve/port

19. AFFERENT RESERVOIR (AR) SYSTEMS - Mapleson A, B and C systems have the reservoir in the afferent limb

20. AR systems - spontaneous breathing - the expiratory valve is separated from the reservoir bag - FGF should be atleast one MV - apparatus dead space is minimal. Not efficient - controlled ventilation FGF close to the expiratory valve ( Mapleson B & C ) , the system is inefficient both during spontaneous and controlled ventilation

21. Mapleson A (Magill’s)

22. MAPLESON A Also known as “ MAGILLS SYSTEM ” Best for spontaneous ventilation Depend on FGF for CO2 washout so also known as “FLOW CONTROLLED BREATHING SYSTEM” No rebreathing if FGF=minute volume No separation of inspired and expired gases Monitoring of ETCO2 is must.

23. APL valve at patient end. FGF and RB at other end of system Only one tubing so mixing of gases Work of breathing is less Length of corrugated tube 110cm / volume=550ml

24. FGF requirements Spontaneous FGF = Minute volume FGF of 51-85ml/kg/min advised to prevent re-breathing Controlled FGF = 2.5 x MV

25. Mapleson A Inspiration The valve closes Patient inspires FG from the reservoir bar FG flushes the dead space gas towards patient Expiration The pt expires into the reservoir bag The initial part of the expired gas is the dead space followed by alveolar gas Meets up with FG,pressure in the circuit increases forces the APL open

26. Mapleson A Controlled Ventilation The Mapleson A is inefficient during controlled ventilation. Venting of gas in the circuit occurs during the inspiratory phase, and the alveolar gases are retained in the tubing during expiration phase Hence the alveolar gas is rebreathed before the pressure in the system increases sufficiently enough to force the expiratory valve open A Fresh gas flow of >20l/min is required to prevent rebreathing during controlled ventilation

27. This system differs from other circuits in that the fresh gas does not enter the system near the patient but near the reservoir bag. Hazard:- should not be used with mechanical ventilator coz entire system becomes dead space

28. Test for Mapelson “A” Occlude patient end, close APL valve, pressurize system – maintaining pressure confirms integritiy

29. LACK’S MODIFICATION In 1976; Lack modified the mapelson A. APL valve at other end Added expiratory limb so no mixing of gas Two arrangement; Dual arrangement( parellel ) Tube within tube(co-axial )

30. Tube length 1.5m Outer tube diameter; 30mm Inner tube diameter ; 14mm Inspiratory capacity ; 500ml

31. TESTING 1)Attach tracheal tube to inner tube at patient end ; blowing down the tube with APL valve closed will produce bag movement if there is leak between two tubes 2) Occlude both limbs at patient end with APL valve open; squeeze the bag; if there is leak in inner tube; gas will escape from APL valve and bag will collapse

32. Advantages:- Location of APL valve- facilitates IPPV / scavenging. Disadvantages:- Slight increase in work of breathing. Break / disconnection of inner tube- entire reservoir tube becomes dead pace.

33. Mapleson B Fresh gas inlet near pt and distal to APL APL opens when pressure in the circuit rises and an admixure of alveolar gas and FG is discharged During Inspiration,a mixture of alveolar gas and FG is inhaled Avoid rebreathing with FGF>2×MV,not very efficient www.anesthesiauk.com

34. Mapleson C Also known as Water to and fro(Water’s Circuit) Similar in construction to the Mapleson B but main tubing shorter FGF is equal to 2×MV to prevent rebreathing CO 2 builds up slowly with this circuit,not efficient www.anesthesiauk.com

35. EFFERENT RESERVOIR (ER) SYSTEMs Mapleson’s D, E ,F and bain circuits 6 mm tube as the afferent limb that supplies the FG from the machine ER systems are modifications of Ayre’s T-piece work efficiently and economically for controlled ventilation

36. MAPELSON D Incorporates T piece at patient RB and APL valve at other end FGF enters the system through side arm of T piece FGF required to prevent rebreathing is 1.5-2 times minute volume Used for spontaneous and controlled ventilation

37. FUNCTIONAL ANALYSIS

38. BAIN’S SYSTEM Described by Bain & Spoerel in 1972 Modification of Mapelson D system Added one more tube; arranged coaxially Inner tube inspiratory ; outer tube expiratory+inspiratory Length of tube: 1.8m Outer tube diameter: 22mm Inner tube diameter : 7mm

39. Fresh Gas Flow required: SPONTANEOUS: 150 – 200 ml/kg/min CONTROLLED : 70 ml/kg/min adult >60kgs 3.5 L/min for 10 – 50 kgs 2L/min for infants < 10kgs

40. ADVANTAGE: Useful for pediatric as will as adult patient Allows warming & humidification of gases useful for spontaneous as will as controlled ventilation Easily dismantled ; sterilised ; so useful in infected cases Facilitates scavenging Length of tubing is long so machine can be taken away from patient ; useful in head & neck & Neurosurgery. Light weight Can be used with ventilator

41. DISADVANTAGE: High fresh gas flow requirements Cannot be used with intermittent flow machine . Disconnection ,kink ,break, leak , at inner tube may go unnoticed – entire exhalation limb becomes dead space

42. Functional Analysis:- During controlled ventilation -when FGF is high, PaCO2 becomes ventilatory dependent. -when MV exceeds FGF , PaCO2 becomes dependent on FGF

43. TESTING (For inner tube) A) Foex-Crempton Smith test Set low flow of O2 on flow meter , close APL valve Occlude the inner tube with a finger or barrel of syringe at pt end . Observe flow meter indicator If inner tube is intact and correctly connected flow meter will fall B) Pathik test Close APL valve, Activate O2 flush Observe the bag Due to venturi effect , Bag will deflate .

44. TESTING (for outer tube) Close APL valve, occlude the patient end & pressurize the system. If no leak pressure will be maintained. When APL valve is opened the bag will deflate easily.

45. Ayre's T-piece Designed as a no valve circuit for paediatrics in 1937 by Philip Ayre. (Later classified as Mapleson E).

46. Mapleson E (Ayers T-Piece) Length = 5cm Diameter = 1cm Side arms = 6mm

47. T-Piece System The Mapleson E (T-Piece),has a length of tubing attached to the T-piece to form a reservoir Uses have decreased because of difficulties in scavenging Still commonly used to administer oxygen or humidified gas to intubated patients breathing spontaneously There are numerous modifications

48. Mapleson E For spontaneous ventilation,the expiratory limb is left open For controlled ventilation,the expiratory linmb is intermittently occulded and fresh gas flow inflate the lungs Rebreathing will depend on the FGF,the volume of the expiratory limb,the patient’s minute vent. And the type of ventilation,i.e. spont versus controlled

49. Our T-Piece

50. Mapleson F(Jackson-Rees System) This is a modification of the T-piece with a bag that has a venting mechanism-usually a hole Adjustable pop-off valve can even be included to prevent over pressuring Scavenging can be done

51. Mapleson F(Jackson Rees) For spontaneous ventilation the relief mechanism is usually left open For assisted of controlled ventilation , the relief mechanism is occluded sufficient enough to distend the bag , respiration can then be controlled by squeezing the bag The volume of the reservoir bag should be approximately the patient’s tidal volume, if the volume is too large re-breathing may occur and if too small ambient air may be entrained To prevent rebreathing the system requires an FGF of 2.5-3 × the patients Minute volume

52. FGF requirements:- Spontaneous- 2-3 times MV Minimum flow 3L/min Controlled- 1000ml + 100ml/kg

53. Advantages Disadvantages Compact Cheap No valves Minimal dead space Minimal resistance to breathing. Ventilator can be used The bag may become twisted and impede breathing High gas flow requirements

54. What FGF’s are needed? Mapleson Systems Uses FGF SV FGF IPPV A Magill Lack Spontaneous Gen Anaesthesia 70-100 ml/kg/min Min 3 x MV B Very uncommon, not in use today C Resuscitation Bagging Min 15 lpm D Bain Spontaneous IPPV, Gen. Anaes 150-200 ml/kg/min 70-100 ml/kg/min E Ayres T Piece Very uncommon, not in use today F Jackson Rees Paediatric <25 Kg 2.5 – 3 x MV Min 4 lpm

55. Relative Efficiency of rebreathing among various Mapleson circuits Spontaneous Ventilation-A>DFE>CB Controlled Ventilation-DFE>BC>A Mapleson A is most efficient during spontaneous ventilation,but it is the worst for controlled ventilation Mapleson D is most efficient during controlled ventilation

56. The blowing of anesthetic gases across a patient’s face Avoids direct connection between a breathing circuit and a patient’s airway Because children resist the placement of a face mask or an IV line, insufflation is valuable CO2 accumulation is avoided with insufflation of oxygen & air at high flow rate(>10 L/m) under H & N draping at ophthalmic surgery Maintain arterial oxygenation during brief periods of apnea Insufflation

57. Draw-over anesthesia

58. Nonrebreathing circuits Use ambient air as the carrier gas Inspired vapor and oxygen concentrations are predictable & controllable Advantage ; simplicity, portability Disadvantage ; absence of reservoir bag -> not well appreciating the depth of TV during spontaneous ventilation Draw-over anestheaia

59. Poor control of inspired gas concentration & depth of anesthesia Inability to assist or control ventilation No conservation of exhaled heat or humidity Difficult airway management during head & neck surgery Pollution of the operating room with large volumes of waste gas Disadvantages of the insufflation & draw-over systems

60. COMBINED SYSTEM HUMPHREY’S ADE system : To overcome the difficulties of changing breathing system for different modes of ventilation this system is developed Two reservoir bag; one in afferent limb; other in efferent limb; only one is in use at a time System can be changed from ARS to ERS by changing the position of lever Used for adults as will as children Functional Analysis same as MAP-A in ARS& as BAIN in ERS

61. HUMPHREY’S ADE MAP-A Map-D

62. CIRCLE SYSTEM ESSENTIAL CPMPONENT: Soda lime canister Two unidirectional valve FGF entry Y piece Reservoir bag Relief valve CRITERIA FOR EFFICIENT FUNCTIONING: Two unidirectional valve on either side of RB Relief valve on expiratory limb FGF should enter proximal to inspiratory unidirectional valve

63. TESTING Set all the gas flows to zero. Close APL valve Occlude Y piece Pressurize system to 30cm of with Oxygen flush Pressure should remain fixed for at least 10 sec. Open APL valve and ensure pressure decrease

64. CIRCLE SYSTEM ctd . ADVANTAGES Exhaled gas –co2 used again and again Constant inspired concentration Conservation of heat & humidity Useful for all ages Useful for low flow ;reduces cost of Anaesthesia Low resistance Less OT pollution DISADVANTAGES : Increased dead space Malfunctioning of unidirectional valve Exhausted soda lime; danger of hypercarbia