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46 Cards in this Set
- Front
- Back
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What is the Function of Anesthetic Machines?
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The anesthetic machine is designed to deliver gas anesthesia to the animal by means of a circuit of corrugated tubing.
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What are the Functions that an Anesthetic Machine must do?
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The Anesthetic Machine Must:
-Deliver oxygen at a controlled flow rate -Vaporize a specific concentration of anesthetic , mix it w/ oxygen, and deliver the mixture to the patient. -Exhaled gases must be moved away from the patient and disposed of or be cleansed of carbon dioxide and then be recirculated to the patient. |
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What does oxygen is a "Carrier Gas" mean?
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It carries the anesthetic gas to the patient and without it, the anesthetic cannot get to the patient!
(Gas Cylinders- contain oxygen or nitrous oxide for delivery to the patient) |
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Why is Oxygen delivered to the patient at 100%?
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Oxygen is delivered @ 100% because:
-The anesthetized patient has a higher metabolic requirement for oxygen than the awake patient. -Anesthetized patient has a reduced tidal volume so less air is inhaled w/ each breath. -Helps to prevent Hypoxia |
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What type of Oxygen Cylinders are designed for Direct Attachment to the anesthetic machine?
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*E Cylinders are commonly used too attach to the anesthetic machine, and the yokes on these canisters match the yoke on the machine.
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What Color are Oxygen Tanks?
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Oxygen cylinders are color coded GREEN.
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Does the Pressure Gage on Oxygen Tanks always show the amount of oxygen left in the tank?
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-*Oxygen amount left in tank can ALWAYS be determined by reading the pressure gauge!
-Pressure gauges on the machine indicate remaining pressure within the tank. |
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Before oxygen enters the Anesthetic Machine, what pressure is it Reduced to?
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This pressure is Reduced to a *safe level of 50 psi Before entering the machine
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What Color are Nitrous Oxide Tanks?
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Nitrous Oxide is stored in BLUE containers
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Why Can't Nitrous Oxide tanks be Attached to Oxygen Yokes?
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The Pin Number on the Yoke is Different than that for Oxygen to Avoid Confusion of the two gases.
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Does the Pressure Gauge on Nitrous Oxide tanks Always Indicate how Full the tank is?
Why or Why Not? |
The pressure in the tank as registered on the gauge does NOT change until All the liquid evaporates.....therefore, the pressure gauge does NOT indicate how Full the tank is. (a tank which is losing pressure, needs to be changed Immediately!)
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Nitrous Oxide info.
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-Full tank contains 770 psi
-Unlike Oxygen tanks where gas exists only in the gaseous state, Nitrous Oxide exists within the tank as a liquid and a gas. |
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What does a Flowmeter do?
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Sets the amount of gas that flows through the machine to be delivered to the patient.
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Flowmeters Reduce the pressure of Oxygen to what level?
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Reduce the pressure of the gas further to 15 psi.
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What does a Vaporizer do?
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Converts Liquid anesthetic into a Gas state at Controlled levels.
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What does the Oxygen Flush Valve do?
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Depressing the Oxygen Flush Valve allows Oxygen to rapidly Bypass the Vaporizer and Enter the Breathing Circuit containing No Anesthetic agents.
*NO anesthetic agent is added to the gas. |
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What is the Fresh Gas Inlet?
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A low pressure hose that carries gas and/or gas mixed w/ anesthetic to the breathing circuit, preventing return of this gas to the previously mentioned components of the machine.
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What is the Reservoir Bag and how does it fill?
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-Inflatable rubber bag
-Fills as gas enters the breathing circuit and deflates as the patient breathes air in -Refills as new gas is supplied to it by the machine (the patient does NOT fill the bag, the machine does) |
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What is the Breathing Circuit?
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The anesthetic Breathing Circuit consists of multipe parts and can be set up in different methods.
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Why would it be necessary to "Bag" the patient?
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-"Bag" the patient: delivery of a breath by manual compression of the bag by the anesthetist. Reasons:
-Periodic bagging helps prevent atelectasis (lack of gas exchange in alveoli). -Flushes the alveoli and airways w/ fresh gas. -Bagging is necessary if the animal is Not breathing on its own. *It is imperative that the bag be filled properly. |
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Describe what the Inhalation & Exhalation Flutter Valves do?
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*Inhalation & Exhalation Flutter Valves allow passage of gas in only one direction.
-Inhalation Flutter Valve opens on inspiration, allowing gas to enter the inhalation hose, pass through the Y-piece, and into the endotracheal tube, then to patient. -On exhalation, the Exhalation Flutter Valve opens and the inhalation flutter valve closes , allowing gas to pass through the exhalation hose to the pop-off valve OR the carbon dioxide scrubber canister. |
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What is the Pop-Off Valve?
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*Pressure relief valve
-Can be open, fully closed, or partially open (determines the type of circuit your using) |
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What position does the Pop-Off Valve need to be in to "Bag" the patient?
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In order to "Bag" the patient, the Pop-Off Valve Must be CLOSED.
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When gas leaves the system through the Pop-Off Valve, where does it go?
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-Gas exits the circuit via the Pop-Off valve and enter the Scavenging System.
-Prevents the buidup of excessive pressure in the system. |
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What is the job of the Carbon Dioxide Scrubber Canister?
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-Gases which do Not exit via the Pop-Off valve enter this canister.
-*Function is to remove carbon dioxide from the exhaled air and deliver it back to the circuit for re-inhalation by the patient. |
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What does the Carbon Dioxide Scrubber Canister contain?
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Soda Lime in the canister contains Ca(OH)2, which cleanses carbon dioxide from the circuit by the following reaction:
2 CO2 + Ca(OH)2 + 2 NaOH -> Na2CO2 + Ca(CO)3 + 2 H2O + heat |
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How do you know when it should be changed?
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-The granules become exhausted after several hours and need to be changed.-Fresh granules can be chipped/crumbled w/ finger pressure, used granules become hard & brittle.
-pH indicator indicates saturation w/ carbon dioxide by turning BLUE. -However, these granules may return to the original color after a few hrs sitting w/o use, so observe the color during anesthesia--Not after. |
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What are the Two products that are produced as a result of the Chemical Reaction and how do they help improve the gases going through the system?
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1. Pressure Manometer: usually situatedon top of the carbon dioxide absorber
-measures pressure within the circuit. 2. Scavenging System: -scavenging systems remove the anesthetic agent from the waste gas which has left the circuit via the pop-off valave. |
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What pressure reading on the Pressure Manometer should Not be exceeded during anesthesia?
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Pressure should NOT exceed 20 mmHg during anesthesia
(mmHg = mm of mercury) |
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What are the 5 Components of the Breathing Circuit?
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Breathing Circuit Consists of:
1. Reservoir Bag 2. Pop-Off Valve 3. Flutter Valves/Hoses 4. Carbon Dioxide Scrubber 5. Pressure Manometer |
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What are the 3 types of Breathing Systems?
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1. Total Rebreathing (closed)
2. Partial Rebreathing (semi-closed) 3. Non-Rebreathing (open) |
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The type of Breathing systems affects:
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-whether the patient rebreathes gases that have been exhaled or does not
-Oxygen & Nitrous Oxide flow rates -Position of the Pop-Off valve (closed or open) -Type of equipment used |
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In regards to Rebreathing Systems-
What is the difference between Closed & Semi-Closed systems? |
*Total Rebreathing System (closed):
-Provides only oxygen necessary -Oxygen flow relatively low *Partial Rebreathing (semi-closed): -Some of the exhaled gases flow through the scrubber and back to the patient -Higher oxygen flow rates |
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In regards to the Rebreathing systems-
What are the safety concerns for this type of system? |
Safety Concerns:
-Not as safe for patients under 14 lbs. (high amount of dead space created) -Carbon Dioxide accumulation (due to poorly functioning scrubber canister; more likely in closed vs. semi-closed systems) -Increased pressure in circuit (keep eye on manometer) -Oxygen depletion -Total rebreahing systems decrease the amount of potential waste gas production **the anesthetic vaporizer setting may need to be 1-2% higher in a closed system vs. a semi-closed system due to low flow rates diminishing vapoizer precision. |
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In regards to a Non-Rebreathing System-
How much gas is returned to the patient? |
*Little or No exhaled gas is returned to the patient.
-No inhalation Fluter Valve: gas flows directly through fresh gas inlet to the inlet hose for delivery to the patient. -Exhaled gas passes through a hose and into a reservoir bag or through a pop-off valve to the scavenging system. |
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In regards to Non-Rebreathing Systems-
How does the Oxygen flow rate compare to a Rebreathing system? |
Requires Higher Oxygen flow rate than a rebreathing system
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What factors help determine which type of circuit to choose?
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Several Factors affect the choice:
-Patient size (<7kg: must use non-rebreathing) -Convenience (non-rebreathing has fewer components) -Cost (*Most Economical=Total Rebreathing, Least Economical=Non-Rebreathing) -Control: slower turnover of gas yeilds longer time to change anesthetic depth (Non-Rebreathing=Rapid change, Rebreathing=Slower change) -Conservation of Heat & Moisture (Rebreathing conserves more) -Production of waste gas (total Rebreathing eliminates production completely; b/c pop-off valve is used) |
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What are the 2 Main Types of Anesthetic Vaporizers?
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1. Precision
2. Non-Precision |
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What Factors affect anesthetic concentration in a carrier gas in an uncompensated vaporizer?
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-Vaporizer setting
-Temperature (Higher temp.=increased volatility of the gas, Colder room=lower concentration vaporized & vice-versa, Higher oxygen flow rates=decreased temp of anesthetic liquid) -Flow Rate (Increased flow=increased concentration vaporized, Decreased flow=lower concentration vaporized) -Back Pressure (Bagging causes back pressure-flow of gas back through vaporizer) |
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What is the difference between a Non-Precision Vaporizer and a Precision Vaporizer?
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Non-Precision Vaporizer:
-For use w/ Low vapor pressure anesthetics -Concentration not precise -Not compensated for temp, gas flow rates, or back pressure *One advantage-effect of carrier gas flow rates Precision Vaporizer: -Delivers Exact concentration -Built in compensation for temp, back flow, and flow rates |
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What does Self-Regulation mean?
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As the patient becomes deeper, breathing and depth slows...less carrier gas...lower concentration of anesthetic in circuit. This process is known as Self-Regulation
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What is the difference between Vaporizer in Circle vs. Vaporizer Out of Circle?
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**Vaporizer in Circle (VIC)=Non-Precision: little resistance to gas flow and are often located inside the circle to aid in self regulation.
**Vaporizer Out of Circle (VOC)= usually Precision: offer High resistance to gas flow and are located outside the circle b/c keeping them inside would cause an increase in dead space. |
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Carrier Gas Flow Rates:
How much gas supplied to the patient is based on several factors: |
Based on several factors:
-Patients Metabolic needs -Patients plane of anesthesia (induction, maintence, recovery) -Period of anesthesia -How rapidly we wish to change anesthetic depth -What type of system is being used -Type of anesthesia being used -****Tidal volume is the basis for our calculation: = 10mL/kg/min |
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Carrier Gas Flow Rates:
Rates for Induction |
Higher rates are used for Induction:
-Saturates the anesthetic circuit w/ oxygen & anesthetic -Dilutes the expired concentration of gases |
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Carrier Gas Flow Rates:
Mask Induction & Chamber Induction |
Mask Induction:
-Flow rate= 30 times the tidal volume -Under 10 kg= 1 to 3L/min -Over 10 kg= 3 to 5 L/min Chamber Induction: 5 L/min |
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Carrier Gas Flow Rates:
Injectable Drugs |
Intubated after Induction w/ Injectable Drugs:
-Use the minute tidal volume= Tidal Volume X # of breaths/min -Commonly used figure= 200 mL/kg/min -No less than 500 mL, No more than 5L |
