Download - Breathing systems open circuit- shoeib
![Page 1: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/1.jpg)
J.J.M MEDICAL COLLEGE, DAVANGEREDEPARTMENT OF ANESTHESIOLOGY
SEMINAR ON BREATHING SYSTEMS OPEN CIRCUIT
CHAIR PERSON PRESENTED BYDR. PRIYADARSHINI M.B DR. SHOEIB M.D P.G IN ANESTHESIAASSISTANT PROFESSORDATE-- 01-06-2010.
![Page 2: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/2.jpg)
“NECESSITY IS MOTHER OF INVENTION”
• Earlier circuits were simple, differing in the type of anesthetic agent administered.
• The purpose of breathing systems that have evolved in anesthetic practice is to deliver Gas & Vapor to the patient in an appropriate, controlled & efficient manner.
![Page 3: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/3.jpg)
• 1846 Sir W.T.G Morton did public demonstration with Ether.
![Page 4: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/4.jpg)
• 1876 Clover`s Inhaler developed by J.T Clover.
![Page 5: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/5.jpg)
• 1907 Barth used it to administer N₂O.
• 1909 Teter`s apparatus developed.
• 1909-13 F.W.Hewitts developed Hewitt`s apparatus.
![Page 6: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/6.jpg)
• 1913 Gwathemy Apparatus developed.
• 1917 Boyle`s Apparatus developed.
• 1928 Magill`s Circuit was developed.
• 1937 Philip Ayre introduced T piece.
![Page 7: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/7.jpg)
• 1972 J.A Bain & W.E Spoerel introduced Bain`s Circuit.
• 1975 Dr Gordon Jackson Rees developed Mapleson F system.
• Humphrey Davy, Brock & Downing developed combined ADE system.
![Page 8: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/8.jpg)
Definition
• A breathing system is defined as an assembly of components, which connects the patient’s airway to the anesthetic machine creating an artificial atmosphere form and into which the patient breathes.
• The breathing system converts a continuous flow from the anaesthesia machine to an intermittent flow;
![Page 9: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/9.jpg)
• In practice the breathing system is usually regarded as extending from the point of fresh gas inlet to the point at which gas escapes to the atmosphere or a scavenging system.
• Rebreathing: in anesthetic systems, it now conventionally refers to the breathing again of some or all of the previously exhaled gases including CO2 & water vapor.
![Page 10: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/10.jpg)
Components of breathing system:
• Formally these were called breathing apparatus or breathing circuits. These names have been abandoned.
It primarily consists ofa) 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 for a gas in the form of a bag or a
corrugated tube to meet the peak inspiratory flow requirements
![Page 11: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/11.jpg)
d) An expiratory port/valve through which the expired gas is vented to the atmosphere.
e) Corrugated tubes for connecting these components.
f) Flow directing valves may or may not be used.
g) A CO2 absorber if total rebreathing is to be allowed.
![Page 12: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/12.jpg)
h) Connectors & adaptors • A connector is a fitting that joins
together 2 or more similar components.
• An adaptor is a specialized connector that establishes functional continuity between otherwise disparate or incompatible components.
• There sizes are universal & either
male/female, 15/22mm connections. Some incorporate gas sampling ports.
![Page 13: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/13.jpg)
i) Bacterial filters- • they prevent
transmission of infection to the patients or contamination of equipments.
• Generally a new filter
should be used for every patient or in the absence of filter, a disposable system should be used on every patient.
![Page 14: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/14.jpg)
j) Heat & Moisture Exchange (HME Filters)-
• These humidify & warm
the Anesthetic gases being delivered to the patients.
• These devices also help to dehumidify the gases that are been sampled for analysis by the side stream devices
![Page 15: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/15.jpg)
RESERVOIR BAGS• Composition Rubber, synthetic
latex, neoprene.• Ellipsoidal in shape.• Available in size ranging from 0.25L
to 6L.• Types
Closed End.Double end.Kuhn`s bag.
![Page 16: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/16.jpg)
• A normal size adult bag holds a volume exceeding the patients inspiratory capacity.
• 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.
![Page 17: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/17.jpg)
• ASTM Standards specifies –
a. For bags < 1.5L, min pressure 30cms. & max pressure 50cms of water.
b. For bags > 1.5L, min pressure more than 35cms & max pressure not exceeding 60cms of water.
![Page 18: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/18.jpg)
Breathing Tubes1. Made of rubber or plastic or
silicone.2. Can be impregnated with silver
to add antimicrobial effect.3. Length is variable.4. Internal diameter
Adults – 22mm. Pediatric – 15mm.
5. Internal volume 400-500ml/m.6. Distensibility 0-5ml/m/mmHg.
![Page 19: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/19.jpg)
7. Resistance to gas flow <1mm of H₂O/litre/min of flow
8. Corrugations prevent kinking & increased flexibility.
9. Backlash seen during spontaneous breathing.10.Wasted ventilation seen during controlled
breathing.
Functions 11.Act as reservoir in certain systems.12.They provide connection from 1part of system to
another.
![Page 20: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/20.jpg)
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 etc
![Page 21: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/21.jpg)
TYPES OF APL VALVES• 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.
![Page 22: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/22.jpg)
• Stem & Seat type
• Control Knob type
• Collection Device & Exhaust Port
![Page 23: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/23.jpg)
• Humphrey Type valve.
APL Valves with Inbuilt• Overpressure Safety devices
![Page 24: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/24.jpg)
Uses of APL valves in spontaneous & controlled ventilation.
• Spontaneous
Valve is kept fully opened.Partial closing will result in PEEP.Pressure <1cm H₂O needed to open valve.Should have pressure drop 1-3cm of H₂O for airflow of
3L/min & 1-5cms of water at 30L/min.
• Controlled
Valve is partially left open.
![Page 25: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/25.jpg)
Essential/ Principle Criteria
The breathing system musta) 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.
![Page 26: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/26.jpg)
Desirable/Secondary Criteria The desirable requirements area) economy of fresh gas.
b) conservation of heat.
c) adequate humidification of inspired gas.
d) light weight
![Page 27: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/27.jpg)
e) Convenience during use.
f) Efficiency 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 mechanical ventilators
h) Provision to reduce theatre pollution
![Page 28: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/28.jpg)
Dripps classification
• It is based on rebreathing, presence or absence of reservoir, CO2 absorption & directional valves.
• Insufflation system – gases are delivered directly into the patient’s airways, no reservoir bag, no valves, no CO2 absorber – open drop method
• Open type – gases are directed to the patient from anesthesia machine, and valves direct exhaled gases to the atmosphere – intermittent flow machines, systems with non rebreathing valves
![Page 29: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/29.jpg)
• Semiopen type – mixing of inspired and expired gases occur and rebreathing depends on fresh gas flow.
• No CO2 absorber – Mapleson systems• Semiclosed system – part of the exhaled gases go
out to the atmosphere, part of it gets mixed with inspired gases and is rebreathed. CO2 absorber is present
• Closed system – complete rebreathing of expired gas. CO2 absorber is present.
![Page 30: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/30.jpg)
Breathing system without CO₂ absorption Breathing system with CO₂ absorption
Unidirectional flow1. Non-rebreathing Valve.2. Circle Systems.
Unidirectional Flow• Circle system with Absorber
Bi Directional Flowa) 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
![Page 31: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/31.jpg)
Breathing systems without CO2 absorber
1) Unidirectional flow• non rebreathing system
– They make use of non-rebreathing valves.– To prevent rebreathing FGF =MV.
![Page 32: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/32.jpg)
Though it satisfies all the 4 essential requirements, still 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
![Page 33: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/33.jpg)
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
![Page 34: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/34.jpg)
2. Bidirectional flow• E.g. Water`s canister• These are obsolete
in current anesthetic practice.
![Page 35: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/35.jpg)
MAPLESON BREATHING SYSTEM
• In 1954 – on advice of William Mushin, Mapleson reported on functional analysis of Breathing systems.
![Page 36: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/36.jpg)
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.
![Page 37: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/37.jpg)
• 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
![Page 38: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/38.jpg)
• For spontaneous ventilation in the order of efficiency – ADCB (All Dogs Can Bite).
• For controlled ventilation – DBCA (Dead Bodies Can’t Argue)
• Here D includes E, F and Bain`s system
![Page 39: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/39.jpg)
Mapleson postulates (1954)
• Mapleson has 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.
![Page 40: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/40.jpg)
• Reservoir bags continues to fill up, without offering any resistance till it is full.
• 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.
![Page 41: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/41.jpg)
Mapleson A/Magill’s system
• Originally described by Evan Magill.
• Length of breathing tube 110-180 cms.
• FGF from machine end.
• APL close to patient.• Sampling ports to be
placed between APL valve & the tube.
![Page 42: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/42.jpg)
• Spontaneous Breathing
3 phases identified
• Inspiratory • Expiratory
• Expiratory Pause.
![Page 43: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/43.jpg)
• To prevent rebreathing FGF=MV is advised.
• FGF = 70 ml/kg/min is recommended.
• Extremely efficient system for spontaneous ventilation.
Function
![Page 44: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/44.jpg)
• mapelsonA.swf
![Page 45: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/45.jpg)
Controlled Ventilation
• These systems are inneficient for controlled ventilation.
• FGF >20L/min required for CO₂ elimination.
• This system cannot be used in patients less than 30kgs.
![Page 46: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/46.jpg)
Lack system
• Co-axial Mapleson A.• Outer tube 30mm in
diameter.• Inner tube 14mm in
diameter.• APL valve placed near
patients end.
Function
![Page 47: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/47.jpg)
Testing for Leaks in Magills & Lacks
Magill – tested for leaks by occluding the patient end & closing valve & pressurizing the system.
• Opening the APL valve will conform proper functioning of the component.
• In addition the user or patient should breathe
through the system to rule out block.
![Page 48: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/48.jpg)
Lack – tested same as for Mapleson A with testing integrity of inner tube.
• ET tube is attached to inner tube & valve is closed. Air is blown. If leak is present, excursions will be seen in the reservoir bag.
• Occlude both the limbs with APL valve open,
squeeze the bag. Any leak is confirmed by release of gas from APL valve.
![Page 49: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/49.jpg)
Mapleson B system
• This circuit functions similarly during both spontaneous & controlled ventilation.
• FGF > 2x Min Volume used for both spontaneous & controlled ventilation.
![Page 50: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/50.jpg)
Mapleson C system
• Also called as Westminster face piece
• FGF > 2 x Min Volume for both Spontaneous & controlled.
• Used for short periods during transportation of patient.
![Page 51: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/51.jpg)
Enclosed Afferent Reservoir System
• Described by Miller & Miller.• Consists of Mapleson A system
enclosed within a non-distensible structure
• Spontaneous ventilation variable orifice kept open, behaves like Mapleson A.
• Controlled ventilation variable orifice partially closed.
• It is more efficient than Bain`s system when FG is > than Alveolar Ventilation.
![Page 52: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/52.jpg)
Efferent Reservoir System
• Mapleson D,E,& F systems, all have a T piece in common.
• T piece is 3 way tubular connector, 1cm in diameter & 5cm in length.
• It has 3 ports 1. To Patient2. The expiratory Port.3. Fresh Gas Port.• FGF = PIFR has been used to
prevent air dilution.
![Page 53: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/53.jpg)
Bain modification of Mapleson D system
• Originally modified by Bain & Sporel in 1972.
• Is co-axial system.• Usual length is 180cm.• Outer tube
– Diameter -22mm.– Carries exhaled gas.
• Inner tube – Diameter-7mm.– Carries fresh gas.
![Page 54: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/54.jpg)
Spontaneous Ventilation
• FGF of atleast 1.5-3 times MV is advised to prevent rebreathing.
• Based on body wt. 200 ml/kg/min flow has been recommended.
![Page 55: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/55.jpg)
Controlled Ventilation
• FGF to maintain normocarbia is advised to be around 70ml/kg/min.
• Most efficient among the Mapleson Systems.
![Page 56: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/56.jpg)
Recommendations by Bain & Sporel
• 2L/min FGF in patients <10kg.
• 3.5L/min FGF in patients between 10-50 kg.
• 70ml/kg/min FGF in patients more than 60kg.
• Tidal volume to be set at 10ml/kg.
• Respiratory rate at 12-16 breaths/min.
![Page 57: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/57.jpg)
Advantages of Bains circuit1) light weight2) convenient to use3) easily sterilized and reusable4) scavenging of exhaled gases is facilitated5) exhaled gases in the outer tubing add warmth tothe inspired gases6) a long corrugated tubing with an aluminium APL
valve may be used to ventilate a patient undergoing MRI
![Page 58: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/58.jpg)
Testing –
For the integrity of the inner tube1) Set a low flow of O2 on the flow meter and
occluding the inner tube (with a finger or the barren of a small syringe) at the patient end while observing the flowmeter indicator.
• If the inner tube is intact and correctly connected, the indicator will fall.
![Page 59: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/59.jpg)
2) Pethick’s test – • High flow O2 is fed into the circuit while the
patient end is occluded until the bag is filled.• The patient end is opened and simultaneously
‘O2 flush’ is activated. • If the inner tube is intact, the Venturi effect
occurring at the patient end, causes a decrease in pressure within the circuit and the reservoir bag deflates.
• Conversely if there is a leak in the inner tube, gas escapes into the outer tube and the reservoir bag remains inflated
![Page 60: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/60.jpg)
Mapleson E system
• Modification of Ayre`s T Piece.• Used initially for pediatric patients
undergoing palate repair & intracranial surgery.
• Minimal dead space, no valves, v.little resistance.
• Volume of expiratory limb > Pts tidal volume to prevent air dilution.
![Page 61: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/61.jpg)
• Used in children weighing 25-30kg.
• Sampling port is between expiratory port & tubing.
• FGF > 3 times min. volume
![Page 62: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/62.jpg)
Problems with this system are
1) Air dilution of the expiratory limb is short.
2) High fresh gas flow is required to prevent rebreathing and air dilution.
3) During controlled ventilation feel of the bag is not there and hence hazard of ‘barotrauma’ is a possibility.
• Used to administer O₂ for spontaneously breathing patients in ICU.
![Page 63: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/63.jpg)
Mapleson F system(JACKSON-REES)
• T piece arrangement with a reservoir bag.• Relief mechanism is either an adjustable valve
at end of bag or a hole on side of Bag.• Newer modification incorporates APL valve
before the reservoir bag. • Pressure relief is actuated at 30cms of water.• FGF = 2-3 x MV for spontaneous respiration.• FGF = Bain`s for controlled respiration.
![Page 64: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/64.jpg)
1) light weight 2) simple construction3) inexpensive4) minimal resistance5) minimal dead space6) controlled ventilation is
easily done7) scavenging is easily
facilitated.
![Page 65: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/65.jpg)
Hazards
1) lack of humidification2) need for high fresh gas flows3) occlusion of relief valve can increase the
airway pressure, producing barotraumas
![Page 66: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/66.jpg)
![Page 67: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/67.jpg)
Advantages of Mapleson systems
1) the equipment is simple, inexpensive and rugged.
2) components can be easily disassembled and can be sterilized.
3) the systems provide buffering effect so that variations in minute volume affect end tidal CO2 less than in a circle system
4) rebreathing will result in retention of heat and moisture
5) resistance is within the recommended ranges
![Page 68: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/68.jpg)
6) light weight and not bulky
7) do not cause excessive drag on ET tube
8) easy to position conveniently.
9) compression & compliance losses are less with these systems than with circle systems.
10) Changes in fresh gas concentration result in
rapid changes in inspiratory gas composition
![Page 69: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/69.jpg)
Disadvantages
1) require high gas flows, higher costs, increased atmospheric pollution.
2) optimal fresh gas flow may be difficult to determine. Necessary to change fresh gas flows when changing from spontaneous to controlled mode.
3) anything that causes decreased fresh gas flow can produce dangerous rebreathing
![Page 70: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/70.jpg)
4) in Mapleson A, B and C system the APL valve is close to the patient end and may be inaccessible.
5) Mapleson E and F are difficult to scavenge.
6) These are not suitable for patients with Malignant Hyperthermia because it may not be possible to increase the fresh gas flow enough to remove the increased CO2 load.
![Page 71: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/71.jpg)
Combined systems• Designed by Humphrey D, Brock
& Downing.• Has 2 reservoirs,
– Afferent– Efferent.
• While in use, only 1 reservoir functions.
• Lever helps in switch over function.
• Can be used in adults as well as in children.
• Not yet widely used.
![Page 72: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/72.jpg)
REFERENCES:• Dorsch J.A, Dorsch S.E. Understanding Anesthesia
Equipment; 4th edition• Ward C S. Anaesthetic Equipment; 2nd edition.• Eisenkraft JB, Ehrenwerth J. Anesthesia Equipment. 1st
edition• Ravishankar M. Man and the Machine – Anesthetic
Breathing Systems• Barasch PG, Cullen BF, Stoelting RK. Clinical
Anesthesia. 5th edition.• Wylie and Churchill Davidsons. A practice of
anesthesia. 5th edition.• RACE 2008- Breathing Circuits by Dr M R Shankar.
![Page 73: Breathing systems open circuit- shoeib](https://reader035.vdocuments.mx/reader035/viewer/2022062719/555427dab4c905987e8b4eeb/html5/thumbnails/73.jpg)