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25 Cards in this Set
- Front
- Back
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What is a rebreathing system |
The animal is allowed to rebreathe its own expired breath CO2 is removed by chemical absorbtion |
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What is a non rebreathing system? |
Fresh gas is continuously supplied, animal does not breathe its own expired gases |
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What is the oxygen requirement for an animal on a rebreathing system? |
Metabolic oxygen requirement |
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What is the requirement for an animal on a non-rebreathing system? |
Minute volume |
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What are the advantages of rebreathing systems? |
Economical Inhaled gases warmed and humidified by the rebreathing process IPPV possivle Reduced pollution Reduced explosion risk |
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What are the disadvantages of rebreathing systems? |
The difference between the imput and what the animal receives in terms of gas is unknown |
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What is the disadvantage of a non rebreathing system? |
Uneconomical at high flow rates i.e. large animals Environmental concerns
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What is an advantage of a non rebreathing system? |
Known compostition of gas delivered Low resistance system Rapid changes in FiAA possible |
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How do we set up a circle to and fro system initially? |
Higher gas concentration at the start and higher flows for de-nitrogenation |
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Why do we need a higher gas concentration at the start of a rebreathing anaesthetic system |
The breath expired contains a much lower concentration of volatile anaesthetic than the inspired air. To maintain the concentration we need to increase flow of anaesthetic until the system has been equilibrated |
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Why do we need de nitrogenation of a rebreathing anaesthetic system |
To prevent the expired nitrogen from the patient lowering the system o2 levels to a hypoxic gas mixture |
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What is low flow anaesthesia? |
Follows a preiod of denitrogenation and stabilisation of the patient This is now the point that fresh gas flow matches O2 and anaesthetic requirements of the patient |
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What are the problems with high resistance in a rebreathing system? |
Hypoventillation and hypercapnia Increased work of breathing so VO2 increases Atelectasis (lung collapse) and hypoxia Positive end expiratory pressure
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How do we minimise resistance in a system? |
Straight hoses Ensure all fixtures and pipes are dry Large and wide parts Non absorbent materials |
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Why is N2O not recommended in rebreathing systems? |
Can lead to hypoxic gas mixtures due to low flow rate and recycling |
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What are the advantages of a To and Fro system |
Simple and rugged Good for field Inexpensive Relatively rabid changes in FIAA possible |
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What are the disadvantages of a To and Fro sytem? |
Bad for dentistry due to valve placement Increased mechanical dead space with duration as the CO2 absorber is used up If not filled correctly Co2 can bypass the absorber and lead to rebreathing Accidental extubation Hyperthermia due to latent heat production in the CO2 absorbtion reaction |
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Whjat are the main types of non rebreathing systems? |
Bag on inspiratory and bag on expiratory limbs |
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What are the "bag on inspiratory limb" systems called? |
Magill Lack and parralel lack |
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What are the advantages of the magill? |
Efficient if the animal spontaneously ventillates |
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What are the disadvantages of the magill? |
Not very good for prolonged IPPV logistically Dead space makes it not suitable for animals <5kg Rebreathing occurs at low flows |
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What is the difference breween the lack and the bain? |
Lack Inspiratory outer tube and expiratory inner tube Bain Inspiratory inner tube and expiratory outer tube |
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Why is the parallel lack better than the lack/coaxial? |
If the inner tube is damaged it could lead to rebreathing parallel lack has 2 separated tubes to this is not a problem |
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What is the advantage of the jackson reese's modification on the ayres t piece? |
Allows IPPV safely |
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What is the advantage of the bain over the lack? |
No issue with rebreathing if inner tube damaged as outer is expiratory Warming of the inspiratory air in inner tube |
