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168 Cards in this Set
- Front
- Back
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What is the third word on the seventh slide of the first vaporizer lecture. (Not the second vaporizer lecture)
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Just kidding....but not really. :(
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What is definition of a vapor
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Vapor is composed of molecules (in a gasseous phase) of a substance that is liquid at room temp and 1 atm of pressure
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What does elevation of temperature do to the rate of vaporization
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It increases it and vice versa for a decrease in temp
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As evaporation proceeds, why does the remaining liquid and its container cool
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Because heat energy is carried from the liquid with the energetic, mobile, evaporating molecules
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As the anesthetic vaporizer cools what could happen to the vaporization rate
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It could limit the rate of further vaproization
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To prevent cooling, what material is used to contain the anesthetic in the vaporizer
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Copper
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Why is copper used in the vaporizer
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It has a high thermal conductivity and a high thermal capacity
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What does the rate of vaporization depend on
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Temperature, vapor pressure of the liquid, partial pressure of the vapor above the evaporating liquid, not on the ambient pressure of the remaining gases present
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Contemporary inhaled volatile anesthetics exist in a liquid state at temps below what
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20 degrees C
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Describe/define saturated vapor pressure
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When a volatile liquid is in a closed container, molecules escape from the liquid phase to the vapor phase until the number in the vapor phase is constant. These molecules bombard the wall of the container and create the saturated vapor pressure
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What is the vapor pressure of Sevoflurane
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160 mmHg
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What is the vapor pressure of Isoflurane
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238 mmHg
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What is the vapor pressure of Halothane
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241 mmHg
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What is the vapor pressure of Desflurane
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664 mmHg
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What is the Boiling point of Sevoflurane
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58.5 deg C
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What is the boiling point of Isoflurane
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48.5 deg C
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What is the boiling point of Halothane
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50.2 deg C
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What is the boiling point of Desflurane
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23.5 deg C
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What is the MAC value of Sevoflurane
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1.7%
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What is the MAC value of Isoflurane
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1.15%
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What is the MAC value of Halothane
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0.77%
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What is the MAC value of Desflurane
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6%
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What is the only liquid anesthetic that can boil at temps that may be encountered in the OR
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Desflurane
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What can result from inadvertently misfilling a vaporizer with an incorrect anesthetic
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The resultant azeotropic mixture can demonstrate different properties than the original 2 anesthetics and may change the output of the aneshtetic vaporizer
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Define latent heat of vaporization
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The amount of energy that is consumed for a given liquid to be converted to a vapor. OR the number of calories required to change 1g of liquid into vapor without a change in temperature.
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Define specific heat of a substance
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The number of calories required to increase the temperature of 1g of any substance 1 deg C.
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Define thermal conductivity
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The measure of the speed at which heat flows through a substance. The higher the thermal conductivity the better the substance conducts heat
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Define Minimum alveolar concentration (MAC)
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Minimum alveolar concentration of an inhaled anesthetic required to prevent 50% of pts from gross pruposeful movement in response to a skin incision
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Which vaporizers are considered to be variable bypass
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Datex-Ohmeda Tec4, Tec5, Tec7 and Drager Vapor 19.n and 20.n
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What does variable bypass refer to
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The method of regulating the concentration of an anesthetic agent output from the vaporizer
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What does the concentration control dial setting determine
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The ratio of flow that goes through the bypass chamber and and the vaporizing chamber as FG from the flowmeters enters the vaporizer inlet
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What is the first thing that the FG flows over on its way to the vaporizing chamber
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The wick system
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True or false: Each variable bypass vaporizer has an agent specific automatic temperature-compensating device
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True
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How are vaporizers agent specific and out of circuit
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Each is designed for a specfic anesthetic agent and to be physically located outside the breathing circuit
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What agents are delivered by variable bypass vaporizers
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Halothane, enflurane, isoflurane, and sevoflurane
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List the components of the variable bypass vaporizer
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Concentration dial, bypass chamber, vaporizing chamber, filler port, filler cap (not listed on the slide, Wick system, temp compensating valve, baffle system)
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Where does the operator fill the vaporizer
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The filler port
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What determines the maximum safe fill level
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The position of the filler port
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What can happen if the vaporizer is overfilled or tilted
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Anesthetic can get into the bypassvaporizing chamber flow and the bypass flow could be carrying saturated anesthetic vapor resulting in overdose chamber.
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Where does flow from the flowmeters enter the vaporizer
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The inlet
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How much of flow is passed through the by pass chamber
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More than 80%
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How much of flow is directed through the vaporizing chamber
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Less than 20%
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Where does flow exit the vaporizer
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The outlet
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What comprises the mixture of gas at the outlet of the vaporizer
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THe combination of flow through the bypass chamber, flow through the vaporizing chamber, and flow of entrained anesthetic vapor
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What is the final concentration of inhaled anesthetic
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The ratio of the flow of inhaled anesthetic to the total gas flow
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What are the vapor pressures of inhaled anesthetics dependant upon
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Ambient room temperature
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At 20 deg C the VP of Isoflurane is 238 mmHg. What would happen if the temp would increase to 35
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It goes up, almost doubles
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At high ambient temps, the VP inside the vaporizing chamber is what
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High
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What are 2 instances where high ambient room temps may increase VP
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Burn pts or peds
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How does the bimetallic strip of the temp compensating valve compensate for high ambient temps/high VP
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It leans to the right decreasing the resistance to flow through the byepass chamber. Thus decreasing flow through the vaporizing chamber increasing flow through thte bypass chamber.
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How does the bimetallic strip of the temp compensating valve compensate for a cold OR/lower VP
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It leans to the left Increasing resistance to the bypass flow. Thus increasing flow through the vaporizing chamber, decreasing flow thorugh the bypass chamber
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What is the net effect of the bimetallic strip leaning to the right or left in a hot or cold OR
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Maintaining constant vaporizer output
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Explain how the expansion element in the Drager 19.n and 20.n reacts to cold and heat
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It expands up in response to higher temps allowing more flow through the bypass chamber and expands down in response to cold to allow more flow through the vaporizer chamber
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True or false: with a fixed dial setting vaporizer output can vary with the rate of gas flowing through the vaporizer
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True
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Where is variation of vaporizer output most notable
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At the extremes of flow rates (highest and lowest)
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Why is output of all variable bypass vaporizers less than the dial setting at rates <250mL/min
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Because of the relatively high density of volatile inhaled anesthetics and insufficient turbulance is generated in the vaporizing chamber to upwardly advance the vapor molecules
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Why is output at high flow rates such as 15 L/min less than the dial setting as well
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Incomplete mixing and failure to saturate the carrier gas in the vaporizing chamber
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What are three factors that can influence vaporizer output
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Flow rate, temperature, and intermittent backpressure
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Other than helping to saturate fresh gas with anesthetic agent what does the wick system help to do
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Because the wick system is on the metal wall, it helps to replace heat/energy lost to vaporization
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What can cause intermittent back pressure
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Positive pressure ventilation and O2 flush valve use
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What term is intermittent back pressure reffered to as and what may it lead to
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The pumping effect. It may lead to higher than expected vaporizer outputs
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Where is the pumping effect more pronounced at
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During low flow rates, low dial settings, and low levels of liquid anesthetics in the vaporizing chamber
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When is the pumping effect increased
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Rapid RR, high peak inspired pressures, and rapid drops in pressure during exhalation
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What makes all of the variable bypass vaporizers immune to the pumping effect
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One way check valves between the vaporizer outlet, the CGO, and smaller vaporizer chambers
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List the safety features of variable bypass vaporizers
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Agent specific, keyed filling devices. Filler port positioned at the maximum safe filling level. Vaporizers are firmly secured to the vaporizer manifold on the AM. Contemporary interlock systems prevent administration of more than one anesthetic at a time.
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What is the name of the vaporizer that is used for Desflurane only
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Datex-Ohmeda Tec 6 Vaporizer
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True or false: Desflurane has a more rapid recovery time than other inhaled agents
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True
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Why does Desflurane have a more rapid recovery time than other inhaled anesthetics
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It has a low blood-gas solubility coefficient
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In what year did the FDA approve Drager;s version of the Tec 6 Desflurane vaporizer
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2004
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The Tec 6 and Tec 6+ are the first vaporizers to be what
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Electrically heated and pressurized
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What is the difference between the Tec 6 and Tec 6+
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The Tec 6+ has an enhanced audible alarm system
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What is the basic setup of the Tec 6s
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They have 2 independent gas circuits arranged in parallel
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Trace the fresh gas flow through the Tec 6s system
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FG from flowmeters enter at the FG inlet and passes through a fixed restrictor (R1) and exits at the vaporizer gas outlet
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Where is the desflurane in the Tec 6 system
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In the desflurane sump in the vapor circuit.
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What does the desflurane sump serve as in the Tec 6 vaporizer
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It serves as the reservoir of desflurane vapor
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At what temp does is the sump electronically heated to
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39 deg C
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At 39 deg C, what is the VP of desflurane
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Approx 1300 mmHg absolute, or 2 Atm absolute
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What is the next portion of the vaporizer circuit, just downstream of the sump
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The sump shut off valve
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If the concentrating control valve is in the on position what does the sump shut off valve do after warms up
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The shut off valve fully opens
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What is the next portion of the vaporizing circuit, just downstream of the sump shut off valve
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The pressure regulating valve
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What does the pressure regulating valve on a Tec 6 do
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Downregulates the pressure from 2 atm to approc 1.1 atm (74 mmHg) absolute at a 10 L/min FGF rate
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How does the operator control the output of desflurane
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By adjusting the concentration control valve (a variable restrictor)
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Where does the FGF meet up with the vapor flow in a Tec 6
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At a point past both restrictors R1 and R2
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At the point where the FGF meets up with the vapor flow in a Tec 6 they are still divorced. How are they interfaced
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Pneumatically and electronically through differential pressure transducers, a control electronic system, and a pressure regulating valve
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When a constant FGF rate encounters the R1 resistor backpressure proportional to the FGF rate builds up and puts pressure against what
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The diaphragm of the control differential pressure transducer
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The differential pressure transducer conveys the pressure difference between the FG circuit and the vapor circuit to what
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The control electronic circuit
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How does the control electronic circuit work
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It senses the pressure difference between the FG circuit and the vapor circuit and adjusts the pressure regulating valve in the vapor circuit to make the pressure equal
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Give the definition of the Tec 6 vaporizer listed in the slides
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The Tec vaporizer is and electrically heated, thermostatically controlled, constant-temperature, pressurized, electrochemically coupled, dual circuit, gas-vapor blender
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The pressure vapor circuit in the Tec 6 is electronically regulated to equal what
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The pressure in the FG circuit
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When the FG flow is increased on a Tec 6 vaporizer what happens to the working pressure
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It increases proportionally
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True or false: Even when varying the FG flow rate the vaporizer output is constant
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True, because the flow through each circuit remains proportional
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What is the only vaporizer that can use all five types of anesthetic gases
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The Datex-Ohmeda Aladin Cassette Vaporizer S/5 ADU
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True or false: The Datex -Ohmeda Aladin Cassette Vaporizer is a variable bypass vaporizer
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True
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How does the Aladin distinguish between anesthetics
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There are seperate, color coded, magnetically coded, cassettes that use agent specific fillers forr each anesthetic agent
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What or who controls the flow control valve in the Aladin
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The CPU
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WHat does the CPU receive input from
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The concetration control dial, the pressure sensor inside the vaporizing chamber, the temp sensor in the vaporizing chamber, flow measurement units inside the bypass chamber and in the outlet of the vaporizing chamber, and the flow meters
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What does the CPU use all of its input to do
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Precisely regulate the flow control valve to obtain the desired vapor concentration output
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Where is the fixed restrictor in the Aladin and what does it do
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It's in the bypass chamber and it causes the flow to split into the bypass chamber and into the vaporizing chamber through a one-way check valve
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What is the importance of the one-way check valve in the Aladin
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It prevents retrograde vapor flow to bypass chamber if using desflurane at temps higher than 23.5 C
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What is the point of the fan in the Aladin
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If using high flow rates large amts of vapor is used and thus cools the liquid anesthetic. The fan forces warmed air from an agent heating resistor across the cassette to raise the temp
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What is the difference in the method of vaporization between the 2 systems
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Variable bypass uses flow over and Injector (Tec 6) has a gas/vapor blender that injects the gas into the FG flow
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How are the 2 types of vaporizers calibrated
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They are calibrated for agent specific use
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How are vaporizers secured to the AM
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By a manifold that holds 2-3 units
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What prevents the user from administering more than one anesthetic at the same time
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The interlock device
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How do you fill the vaporizers
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Turn them off, check the correct agent, and pour it in
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How do you figure out % concentration of an inhaled agent
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VP of the agent/(BPx100)
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What are the devices called that prevent you from pouring a wrong anesthetic into the vaporizer
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Key type filling devices
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Describe the breathing cicuit
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It is a large bore, corrugated hose that provides a flexible, low resistance, lightweight connection from one part of the system to another
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Is the scavenging system considered part of the breathing system
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Nope
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When the mixture of gases exits the AM where does it exit to
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The breathing circuit
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Where does the breathing circuit start and end
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It usually extends from the FG inlet to the point at which the gas escapes to the atmosphere or scavenging system
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What are the basic functions of the breathing system
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Receive gas mixture from AM, deliver gas to the pt, remove CO2 and conditions temp and humidity to inspired gas, allows AM's continuous flow to be converted to intermittent, allows spontaneous, controlled, and assisted respiration, as well as provide other functions such as gas sampling and airway pressure, flow, and volume monitoring
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When were the first anesthetics administered
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150 yrs ago
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What are the four classifications of breathing circuits
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Open, semi-open,semi-closed, closed
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What is the classification of breathing circuits based on
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Whether a reservoir (breathing bag) is present and the degree to which rebreathing occurs
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What is the only system that has access to atmosphere
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Open
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What are the three classifications in which a reservoir is able to be used
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Semi-open, semi-closed, closed
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Both nonrebreathing systems (Mapleson, Bain) and the circle system are what when the FGF> than minute ventilation
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Semi-open
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True or False: Some rebreathing occurs when FGF to the circle system is less than minute ventilation
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True
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In a closed system, low FGF, and APL valve closed rebreathing is what
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Total
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Which breathing systems have exhaled gases containing CO2 removed from the system
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Nonrebreathing systems
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The amount of rebreathing varies inversely with what
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FGF
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Define mechanical dead space
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The volume in a breathing circuit occupied by gases that are rebreathed without any change in composition
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What can minimize mechanical dead space
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Seperating the inspiratory and expiratory gas stream as close to the patient as possible
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What are some examples of mechanical dead space
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The ETT extending beyond the pt's incisors, monitor adaptors, any adaptors used to facilitate pt positioning, the volume within the mask, humidification management exchangers, and the y-piece
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What are some advantages of rebreathing
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There is an increase in tracheal warmth and humidity and there is a reduced risk of exposure of waste gases. Also, costs can be reduced and there is less environmental impact as more anesthetic gases are used as opposed to leaving to the scavenging system
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What are the effects of rebreathing O2 and N2
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O2 nothing, but N2 rebreathing slows induction
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How can you avoid rebreathing during induction
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Use higher FGF
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Why are ventilator tidal volumes set much larger than spontaneous breaths
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To compensate for the mechanical dead space
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Where does dead space end
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Where inspiratory and expiratory stream converge, at the Y-piece in circle systems
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How does the AM avoid being colonized with bacteria and corrosion
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Using dry gases
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What type of humidification is used and why
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Passive humidification. Active is less effective at preventing hypothermia, the added moisture can clog gas analysis lines and soda lime granules, or obstruct unidirectional valves
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What are common features of nonrebreathing circuits
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All lack unidirectional valves, all lack CO2 soda-lime absorption, amount of rebreathing is highly dependent on gas flow, amount of resistance is low (no unidirectional valves)
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In a non-rebreathing circuit what is used as a CO2 washout
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High FGF
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In the Mapleson Systems what letters are used
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A-E and F was added in 1975
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What are the common components of the Mapleson system
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Facemask, spring-loaded pop-off valve, reservoir tubing, FG inflow tubing, reservoir bag
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What are the three distinct functional groups of the Maplesonsystem
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A, BC, DEF
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Describe the Mapleson A (Magill) circuit
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There is a spring loaded pop-off valve near the mask. FGF enters the circuit near the reservoir. A corrugated tube connects the the bag to the APL at the end of the pt's system
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In the Mapleson A, during spontaneous ventilation, what position is the APL valve kept in
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Fully open
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In the Mapleson A, during assisted or controlled ventilation what position is the APL valve kept in
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Partially closed. This way when the bag is squeezed there is enough pressure to inflate the lungs, During inspiration the valve opens.
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Which Mapleson System is the most efficient during spontaneous ventilation
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Mapleson A
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During spontaneous respiration, the Mapleson A requires what FGF rate to prevent rebreathing
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1 times the minute ventilation
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Which Mapleson system has the worst efficiency during controlled ventilation
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Mapleson A
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During controlled ventilation what FGF rate is required in the Mapleson A to prevent rebreathing
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As high as 20L/min
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Describe the Mapleson B&C system
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The Spring-loaded POV is located near the mask and the FG inlet tubing is near the patient. The tubing and breathing bag serve as a blind limb where gases can accumulate
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Why is the B&C system less efficient than the D,E,&F system
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It requires higher flow rates to minute ventilation than D, E, &F
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In B&C during spontaneous ventilation what position is the APL valve in
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Fully open. Excess gas is vented during exhalation
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B&C during assisted or controlled ventilation the APL is in what position
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Closed sufficiently to allow the lungs to expand. Excess gases are vented during inspiration
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What are the FGF rates for B&C during spontaneous and assisted/controlled ventilation
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2 times VE for spontaneous, 2-2.5 times VE for controlled
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What Mapleson systems are collectively referred to as the T-piece group
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D,E,&F
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Describe the Mapleson DEF systems
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FGF enters near the patient and excess gas exits at the opposite end of the circuit
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Which system group is more efficient B,C or D,E,F
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D,E,F as 2.5 times VE is required to prevent rebreathing
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How is rebreathing prevented in Mapleson D
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During the expiratory phase, FGF fills the limb forcing exhaled gas distally towards the bag
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What is the convenience of Mapleson E
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It provides a convenient way of switching between A and DE arrangements. It also makes it particularily easy to perform IPPV
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What is benefit of the Mapleson F (also referred to the Jackson-Rees modification of Ayre's T-piece)
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It offers very low resisatnce to breathing and can be used for almost any age
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What should the FGF rate be for the Mapleson F
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2-3 times VE. Minimum of 5L/min
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List the factors that affect rebreathing
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FG inflow rate, MV, mode of ventilation, TV, RR, CO2 sample site, I:E ratio, Peak Insp flow, Volume of reservoir tube, volume rebreathing bag, volume of mask, ventilation through an ETT
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What is the most popular non-rebreathing circuit in the US
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The Bain System
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What is the Bain system most similar to
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Mapleson D
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What is a benefit of using the Bain system
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The setup gives inhaled gases greater heat and humidity
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In the Bain system what FGF rate is needed to prevent rebreathing
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2.5 time VE
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What is a disadvantage of the Bain system
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Unrecognized kinks can conver the limb to dead space
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What test must be performed to the Bain system to detect faulty inner tubes in the coaxial bain circle
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Pethick's test
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List the advantages of nonrebreathing systems
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Light, convenient, easily sterilized and scavanged, exhaled gases in limb can give heat and humidity to inhaled gases
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List the disadvanteages of nonrebreathing systems
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Unrecognized kinking leads to dead space, higher flows required, loss of heat from pt, requires disconnection for assembly, can be assembled incorrectly
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The circle breathing system is reffered to as what
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Universal F or single limb
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How is rebreathing of CO2 prevented in the circle breathing system
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CO2 absorbant
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Gases other than CO2 can be rebreathed in the circle system. How is this prevented.
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Arrangement of the cicuit components and adjusting the FGF rate
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