Anesthetic Breathing Circuits By Dr Ahmed Mostafa Assist

Anesthetic Breathing Circuits By Dr. Ahmed Mostafa Assist. Prof. of anesthesia & I. C. U.

Insufflation method • Definition: It the blowing of anesthetic gases across a patient's face. • Uses: Pediatric inductions with inhalation anesthetics. Maintain arterial oxygenation during brief periods of apnea (e. g. during bronchoscopy).

Insufflation method • Methods: Cupped hand containing the end of the gas delivery tube. Edinburgh face mask. Mouth cannula. Nasal cannula. Simple O 2 mask. Venturi O 2 mask.

Insufflation method • Advantages: Avoids direct connection between a breathing circuit and a patient's airway. There is no rebreathing of exhaled gases especially if the flow is high enough. • Disadvantages: Poor control of inspired gas concentration and depth of anesthesia. Inability to assist or control ventilation. No conservation of exhaled heat or humidity. Difficult airway management during head and neck surgery. Pollution of the operating room with large volumes of waste gas.

Open-Drop Anesthesia • Although open-drop anesthesia is not used in modern medicine, its historic significance warrants a brief description here. A highly volatile anesthetic most commonly ether or halothane is dripped onto a gauze-covered mask (Schimmelbusch mask) applied to the patient's face. As the patient inhales, air passes through the gauze, vaporizes the liquid agent, and carries high concentrations of anesthetic to the patient. • A modern derivative of open-drop anesthesia utilizes draw-over vaporizers that depend on the patient's inspiratory efforts to draw ambient air through a vaporization chamber. This technique may be used in locations or situations in which compressed medical gases are unavailable (e. g. developing countries and battlefields).

MAPLESON CIRCUITS Components of Mapleson Circuits: Breathing Tubes: Corrugated. Made of rubber (reusable) or plastic (disposable) The large diameter of the tubes (22 mm) To minimize FGF requirements, the volume of the breathing tube should be at least as great as the patient's tidal volume. Minimal compliance.

MAPLESON CIRCUITS Components of Mapleson Circuits: Fresh Gas Inlet: Adjustable Pressure-Limiting (APL) Valve (Pressure-Relief Valve, Pop-off Valve): APL valve controls this pressure buildup. The APL valve should be fully open during spontaneous ventilation. Assisted and controlled ventilation require positive pressure during inspiration to expand the lungs. Partial closure of the APL valve limits gas exit, permitting positive circuit pressures during reservoir bag compressions.

MAPLESON CIRCUITS Components of Mapleson Circuits: Reservoir Bag (Breathing Bag): Function: Reservoir of anesthetic gas. Method of generating positive-pressure ventilation.

MAPLESON CIRCUITS Components of Mapleson Circuits: Reservoir Bag (Breathing Bag): Compliance: • High compliance as their volume. • Three distinct phases of reservoir bag filling are recognizable:

MAPLESON CIRCUITS Components of Mapleson Circuits: Reservoir Bag (Breathing Bag): Compliance: i. phase I : After the nominal 3 -L capacity of an adult reservoir bag is achieved. ii. phase II: pressure rises rapidly to a peak. iii. phase III: Further increases in volume result in a plateau or even a slight decrease in pressure. This ceiling effect helps to protect the patient's lungs against high airway pressures if the APL valve is unintentionally left in the closed position while fresh gas continues to flow into the circuit.

MAPLESON CIRCUITS Classification and Characteristics of Mapleson Circuits: 1. Mapleson A(Magill system):

MAPLESON CIRCUITS Classification and Characteristics of Mapleson Circuits: 1. Mapleson A(Magill system): Description: The FGF inlet and reservoir bag are away from the patient. The spill valve is close to the patient.

MAPLESON CIRCUITS Classification and Characteristics of Mapleson Circuits: 1. Mapleson A(Magill system): Required fresh gas flow: Spontaneous ventilation: . Equal to minute ventilation (80 m. L/kg/min). . The most efficient. Controlled ventilation: the least efficient.

MAPLESON CIRCUITS Classification and Characteristics of Mapleson Circuits: 1. Mapleson A(Magill system):

MAPLESON CIRCUITS Classification and Characteristics of Mapleson Circuits: 2. Lack system(Coaxial Magill system):

MAPLESON CIRCUITS Classification and Characteristics of Mapleson Circuits: 2. Lack system(Coaxial Magill system): Description: It has two tubes with the same axis, the outer one (22 mm diameter) through which inspiration occurs and a narrow inner tube (7 mm diameter) through which expiration occur, so resistance tom expiration may occur.

MAPLESON CIRCUITS •

MAPLESON CIRCUITS Classification and Characteristics of Mapleson Circuits: 2. Lack system(Coaxial Magill system):

MAPLESON CIRCUITS Classification and Characteristics of Mapleson Circuits: 3. Mapleson B:

MAPLESON CIRCUITS Classification and Characteristics of Mapleson Circuits: 3. Mapleson B: Description: The reservoir bag is away from the patient. The FGF inlet and spill valve are close to the patient.

MAPLESON CIRCUITS •

MAPLESON CIRCUITS Classification and Characteristics of Mapleson Circuits: 4. Mapleson C (Waters' to-and-fro): Description: The reservoir bag, the FGF inlet and spill valve are close to the patient. No corrugated tube. Required fresh gas flow: as Mapleson B.

MAPLESON CIRCUITS Classification and Characteristics of Mapleson Circuits: 5. Mapleson D:

MAPLESON CIRCUITS Classification and Characteristics of Mapleson Circuits: 5. Mapleson D: Description: The spill valve and reservoir bag are away from the patient. The FGF inlet is close to the patient.

MAPLESON CIRCUITS •

MAPLESON CIRCUITS •

MAPLESON CIRCUITS Classification and Characteristics of Mapleson Circuits: 6. Bain system: • The Bain circuit is a popular modification of the Mapleson D system.

MAPLESON CIRCUITS Classification and Characteristics of Mapleson Circuits: 6. Bain system: Description: It has two tubes with the same axis, the outer one (22 mm diameter) through which expiration occurs and a narrow inner tube (7 mm diameter) through which inspiration occur.

MAPLESON CIRCUITS •

MAPLESON CIRCUITS Classification and Characteristics of Mapleson Circuits: 6. Bain system: Advantages: Decreases the circuit's bulk Retains heat better than the Mapleson D circuit as a result of partial warming of the inspiratory gas by the surrounding warmer expired gases. Improve humidification due to partial rebreathing. Some types of automatic ventilators can be connected to it.

MAPLESON CIRCUITS Classification and Characteristics of Mapleson Circuits: 6. Bain system: Disadvantages: The possibility of kinking or disconnection of the fresh gas inlet tubing. If unrecognized, it results in significant rebreathing of exhaled gas. Large waste of gases.

MAPLESON CIRCUITS Classification and Characteristics of Mapleson Circuits: 6. Bain system:

MAPLESON CIRCUITS Classification and Characteristics of Mapleson Circuits: 7. Mapleson E (Ayre’s T piece):

MAPLESON CIRCUITS Classification and Characteristics of Mapleson Circuits: 7. Mapleson E (Ayre’s T piece): Description: The FGF inlet is close to the patient. No bag or valves are present.

MAPLESON CIRCUITS •

MAPLESON CIRCUITS Classification and Characteristics of Mapleson Circuits: 7. Mapleson E (Ayre’s T piece):

MAPLESON CIRCUITS Classification and Characteristics of Mapleson Circuits: 7. Mapleson F (Jackson Rees modification of Ayre’s T piece): Description: The FGF inlet is close to the patient. The bag is added away from the patient to allow controlled ventilation and scavenging. No valves are present.

MAPLESON CIRCUITS •

MAPLESON CIRCUITS Efficiency of Mapleson Circuits: Breathing-circuit efficiency is measured by the fresh gas flow required to eliminate, as much as possible, CO 2 rebreathing. Because there are no unidirectional valves or CO 2 absorption in Mapleson circuits, rebreathing is prevented by venting exhaled gas through the APL valve before inspiration. There is usually some rebreathing in any Mapleson circuit. The flow through the circuit controls the amount. To attenuate rebreathing, high fresh gas flows are required.

THE CIRCLE SYSTEM - The carbon dioxide absorber canister is labeled (C). - The breathing bag (B). - Inspiratory valve (Vi). - Expiratory valve (Ve). - pressure relief valve (V). - Fresh gas supply (F).

THE CIRCLE SYSTEM Components of the Circle System:

THE CIRCLE SYSTEM 1. FGF Source. 2. Unidirectional valves. 3. Inspiratory and expiratory corrugated tubes. 4. AY- piece connector. 5. Adjustable pressure limiting valve. 6. A reservoir bag. 7. Ventilator bag switch. 8. Carbon Dioxide Absorbent.

THE CIRCLE SYSTEM

THE CIRCLE SYSTEM Carbon Dioxide Absorbent Types: 1. Soda lime. 2. Bara Lime. 3. Amsorb.

THE CIRCLE SYSTEM Carbon Dioxide Absorbent Types: 1. Soda lime: Is the more common absorbent and is capable of absorbing up to 23 L of CO 2 per 100 g of absorbent.

THE CIRCLE SYSTEM Carbon Dioxide Absorbent Types: 1. Soda lime: Its reactions are as follows: CO 2 + H 2 O H 2 CO 3 + 2 Na. OH Na 2 CO 3 + 2 H 2 O + Heat. (Fast reaction) Na 2 CO 3 + Ca(OH)2 Ca. CO 3 + 2 Na. OH. (Slow reaction)

THE CIRCLE SYSTEM Carbon Dioxide Absorbent Types: 2. Bara Lime: Its reactions are as follows:

THE CIRCLE SYSTEM Carbon Dioxide Absorbent Comparison of Soda Lime and Barium Hydroxide Lime Soda Lime Barium Hydroxide Lime Mesh size 1 4– 8 Method of hardness Silica added Water of crystallization Content Calcium hydroxide (94%) Barium hydroxide (80%) Sodium hydroxide (5%) Calcium hydroxide Potassium hydroxide (1%) Usual indicator dye Ethyl violet Absorptive capacity (liters of CO 2/100 g granules) 14– 23 9– 18 water content 14– 19%

THE CIRCLE SYSTEM Carbon Dioxide Absorbent Indicator Dye Changes Signaling Absorbent Exhaustion Indicator Color when Fresh Color when Exhausted Ethyl violet White Purple Phenolphthalein White Pink Clayton yellow Red Yellow Ethyl orange Orange Yellow Mimosa 2 Red White

THE CIRCLE SYSTEM Carbon Dioxide Absorbent Types: 3. Amsorb: - Has greater inertness than soda lime or barium hydroxide lime. - less degradation of volatile anesthetics. - It is consisting of: Calcium hydroxide, Calcium chloride, Calcium sulfate and Polyvinyl-pyrrolidone added to increase hardness.

THE CIRCLE SYSTEM Carbon Dioxide Absorbers: The granules of absorbent are contained within one or two canisters that fit snugly between a head and base plate.

THE CIRCLE SYSTEM Performance Characteristics of Circle System: Fresh Gas Requirement: The circle system prevents rebreathing of CO 2 at low fresh gas flows that (≤ 1 L) or even fresh gas flows equal to the uptake of anesthetic gases and oxygen by the patient and the circuit itself.

THE CIRCLE SYSTEM Performance Characteristics of Circle System: Fresh Gas Requirement: At fresh gas flows greater than 5 L/min, rebreathing is so minimal that a CO 2 absorber is usually unnecessary.

THE CIRCLE SYSTEM Performance Characteristics of Circle System: Fresh Gas Requirement: With low flows, concentrations of O 2 and inhalation anesthetics can vary markedly between fresh gas and inspired gas.

THE CIRCLE SYSTEM Performance Characteristics of Circle System: Fresh Gas Requirement: The greater the fresh gas flow rate, the less time it will take for a change in fresh gas anesthetic concentration to be reflected in a change in inspired gas anesthetic concentration.

THE CIRCLE SYSTEM Performance Characteristics of Circle System: Fresh Gas Requirement: Higher flows speed induction and recovery, compensate for leaks in the circuit, and decrease the risks of unanticipated gas mixtures.

THE CIRCLE SYSTEM Performance Characteristics of Circle System: Dead Space: Any increase in dead space must be accompanied by a corresponding increase in tidal volume if alveolar ventilation is to remain unchanged.

THE CIRCLE SYSTEM Performance Characteristics of Circle System: Dead Space: Because of the unidirectional valves, apparatus dead space in a circle system is limited to the area distal to the point of inspiratory and expiratory gas mixing at the Y-piece.

THE CIRCLE SYSTEM Performance Characteristics of Circle System: Resistance: The unidirectional valves and absorber increase circle system resistance, especially at high respiratory rates and large tidal volumes. Nonetheless, even premature neonates can be successfully ventilated using a circle system.

THE CIRCLE SYSTEM Performance Characteristics of Circle System: Humidity and Heat Conservation: • the heat and humidity of inspired gas depend on the relative proportion of rebreathed gas to fresh gas.

THE CIRCLE SYSTEM Performance Characteristics of Circle System: Humidity and Heat Conservation: High flows are accompanied by low relative humidity, whereas low flows allow greater water saturation. Absorbent granules provide heat and moisture in the circle system.

THE CIRCLE SYSTEM Performance Characteristics of Circle System: Bacterial Contamination: • There is slight risk of microorganism retention in circle system components. For this reason, bacterial filters are sometimes incorporated into the inspiratory or expiratory breathing tubes or at the Y-piece.

THE CIRCLE SYSTEM • Advantages of the circle system: 1. More economic. 2. Preserve heat and humidity. 3. Decrease the risk of pollution of the operating room.

THE CIRCLE SYSTEM • Disadvantages of the Circle system: 1. Greater size and less portability. 2. Increased complexity. 3. Higher risk of disconnection or malfunction 4. Increased resistance. 5. The difficulty of predicting inspired gas concentrations during low fresh gas flows.

THE CIRCLE SYSTEM • Monitoring during low anesthesia: 1. O 2 analyzer: to measure inspired O 2 concentration. 2. Capnography: to measure end-tidal CO 2. 3. Multi-gas analyzer: to measure anesthetic gas concentration.

THE CIRCLE SYSTEM • Disadvantages of low flow and closed circuit: I. Disadvantages of low FGF: - Unpredictable concentration of O 2 and volatile anesthetics. - Accumulation of foreign trace gases as: Methane from the intestine , acetone from the liver, ethanol in alcoholic patients, carbon monoxide in heavy smokers. - Does not compensate for leaks.

THE CIRCLE SYSTEM • Disadvantages of low flow and closed circuit: II. Disadvantages of CO 2 absorbents ( The interaction between CO 2 absorbent and inhalational anesthetics): a) Haloalkene toxicity: Halothane degradation Sevoflorane degradation BCDFE which is nephrotoxic in rats. Compound A which is nephrotoxic in rats.

THE CIRCLE SYSTEM • Disadvantages of low flow and closed circuit: II. Disadvantages of CO 2 absorbents ( The interaction between CO 2 absorbent and inhalational anesthetics): b) Carbon monoxide toxicity: - Cause: Dry absorbent. - Occur with desflurane, enflurane, or isoflurane.

THE CIRCLE SYSTEM • Disadvantages of low flow and closed circuit: II. Disadvantages of CO 2 absorbents ( The interaction between CO 2 absorbent and inhalational anesthetics): b) Carbon monoxide toxicity: - The incidence of carbon monoxide formation is not known but is probably greater than thought. - Cases of severe carbon monoxide poisoning have been reported.

THE CIRCLE SYSTEM • Disadvantages of low flow and closed circuit: II. Disadvantages of CO 2 absorbents ( The interaction between CO 2 absorbent and inhalational anesthetics): b) Carbon monoxide toxicity: Reported at: - The first general anesthetic of the day and on Monday morning. - A little-used machine in a remote location.

THE CIRCLE SYSTEM • Disadvantages of low flow and closed circuit: II. Disadvantages of CO 2 absorbents ( The interaction between CO 2 absorbent and inhalational anesthetics) III. Disadvantages of circuit system: discussed before.

RESUSCITATION BREATHING SYSTEMS

RESUSCITATION BREATHING SYSTEMS • Resuscitation bags (AMBU bags or bag-mask units) are commonly used for emergency ventilation. A resuscitator is unlike a Mapleson circuit or a circle system because it contains a non-rebreathing valve.

RESUSCITATION BREATHING SYSTEMS • Advantages: - Simple. - Portable. - Ability to deliver almost 100% oxygen.

RESUSCITATION BREATHING SYSTEMS • Disadvantages: - They require high fresh gas flows to achieve a high FIO 2. - The maximum achievable tidal volumes are less than those that can be achieved with a system that uses a 3 -L breathing bag.

Thank you DR. AHMED MOSTAFA