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NU 568

Exam 4 - CO2 Absorbers and Vaporizers

QuestionAnswer
What 3 things does the rate of vaporization depend on? 1)temperature 2)vapor pressure of the liquid 3)partial pressure of vapor above the liquid
What does the concentration of dissolved gas depend on? Partial pressure of the gas
What does the partial pressure control? # of gas molecule collisions w/surface of the solution
What happens to the number of gas molecule collisions if the partial pressure is doubled? Molecule collisions is doubled
What is the latent heat of vaporization? Amt of heat necessary to vaporize a given qty of a substance (i.e. liquid to vapor)
What is the heat of vaporization of water? 540 calories
What is the difference b/w endo- and exo- thermic rxns? Endo absorb energy, exo release energy+heat
Liquid to gas = (endo/exo) Endo
Gas to liquid = (endo/exo) Exo
What does a gas molecule of an anesthetic bouncing off the wall of its container create? Vapor pressure for that agent
Vaporization requires _______. Energy
As vaporization proceeds, the temperature of the liquid (rises/drops), and vaporization is (increased/decreased). Drops; decreased
As vaporization proceeds, the surrounding temperature also (increases/decreases). Decreases
During the process of vaporization, moisture in the air may become what product? ice crystals
What two properties of copper enhance its properties as a vaporizers to maintain a constant temp? High specific heat and thermal conductivity
What is specific heat? Quantity of heat req'd to raise the temp of 1gram of substance by 1degree celsius
What is thermal conductivity? Speed of heat conductance
From lowest to highest, what are the vapor pressures for sevo, iso, halothane, and des? (all at 20C) mmHg: 160, 240, 243, 681
What determines the ultimate concentration of anesthetic delivered? Flow through the vaporizer
The copper kettle is classified as a ________. Measured flow vaporizer
How does knowledge of the vapor pressure of an anesthetic serve the anesthetist? Allows them to calculate the delivered concentration
Which vaporizer is similar to the copper kettle and utilized by the military? Vernitrol
What does the user calculate with the Vernitrol? User calculates the amt of gas to be bubbled through the vaporizer
What are the different variable bypass flow-over vaporizers? TEC 4,5,7
What is the splitting ratio? Gas entering the vaporizing chamber divided by the total FGF
The gas sent through the vaporizing chamber, as adjusted by the dial, is called _____ or ____. Chamber flow; carrier gas
What two things does the Tec 4 utilize to ensure full saturation of the carrier gas? Wicks and baffles
What happens to the chamber gas after it is saturated? Dilution with the balance of FGF (bypasses the chamber)
The final desired concentration is produced at the ______ and then delivered to the patient. vaporizer outlet
What are 4 major characteristics of modern vaporizers? 1)agent specific 2)deliver constant vapor [] regardless of changes in temp/pressure/chamber flow 3)fractionalizes gas flow (variable bypass) 4)"Out of circuit" vaporizers
What are "out of circuit" vaporizers? Vaporizers positioned outside of the circle system
What is the benefit of out of circuit vaporizers? Delivers precise amounts of anesthetic
True/False: The delivered concentration of anesthetic gas is not diluted when delivered to the patient. False-may be diluted by gas present in the circuit (O2/Air/N2O)
What does the rate of change of concentration in the circuit depend on? FGF
What does high FGF achieve? Faster equilibration
True/False: All variable bypass vaporizers must be turned off prior to filling? True
Which vaporizer can be refilled even with FGFs on? TEC6 (desflurane)
What are the FGF limits when refilling desflurane? <8L/min and % is less than 8%
Identify the anesthetic gas vaporizer that is not accurate at high FGF and explain why. Sevo b/c of its low vapor pressure
The Tec6 vaporizer is used only with ________. Desflurane
Which vaporizer needs to be plugged in to operate a heating element? Tec6
What are the two control points in the Tec6? Pt1=concentration of anesthetic, controlled by dial; Pt2=transducer that responds to level of FGF
The internal element of the Tec6 heats up to _____ with a vapor pressure of _____ in this section of the vaporizer. 39C; 1500mmHg
What would be the result of putting des into a variable bypass vaporizer? (i.e. sevo) Would result in delivering hypoxic mixture (5% of delivery of des in a sevo vaporizer would equal 19MAC with 100% vapor output to the patient)
What are the steps in the vaporizer check out? 1)Check low battery indicator 2)Hold "Mute" for 4 seconds and all lights and alarms activate 3)Turn vaporizer onto 1% and d/c plug-->replace the battery if light and alarm do not activate after 15sec
What are possible causes of the no output alarm for the Tec6? 1)device tilted >10deg 2)power failure >10sec 3)internal malfxn
What should be done with a Tec6 malfunction? Immediately switch to another agent to prevent emergence
All modern vaporizers (increase/decrease) concentration with counterclockwise turning of the dial. Increase
What is important about the removal of a vaporizer with the Drager Vapor 19.1? Have to use a machine block to prevent leaks
True/False: The Drager Vapor 19.1 can tolerate minor tips of the vapor canisters. False-if tipped, take out of service per manufacturer recommendations
What feature helps compensate for changes in temperature? Bi-metallic strip
What are the changes to the bimetallic strip with high and low temps? High temp=stretches up and to the left; low temp=leans right and compresses down
Define splitting ratio. One gas bypasses the vaporizing chamber while another gas passes through the chamber to pick up vapor
What are two features of the Vapor 2000 not scene on its predecessor, the Drager Vapor 19.1? Tippable canisters (in the "T" position) and unique key lock filling system
Which machine utilizes cassettes with control wheels to adjust concentrations of gases? Datex Ohmeda ADU
True/False: The cassettes for the Datex Ohmeda ADU are tippable. True
What are possible hazards r/t to contemporary vaporizers? (5) 1)filled w/wrong agent 2)unpredictable delivery if tipped beyond 45deg 3)overfilling 4)out of calibration 5)incorrect hanging on back bar 6)missing gaskets/fillers
Intermittent back pressure from the breathing circuit is known as ______. Pumping effect
Pumping effect can be caused by back pressure from the breathing circuit or from the _______. O2 flush valve
What can back pressure lead to? Increased vapor output
What features on modern vaporizers have to decrease the pumping effect? Check valves between the vaporizer outlet and the CGO; reduced vaporizing chamber size; baffled inlet chambers (also, wicks, baffles, channels and check valves)
In relation to FGF and agent levels, when is the pumping effect seen? Low: agent, FGF, volume%
What is the pressurizing effect? Decreased []'s of the anesthetic agent d/t increased []'s of the carrier gas
How does pressurizing affect vaporizers? Decreases vaporizer output and performance
In what scenario can the pressurizing effect be scene? In what systems does it not occur? Seen with high FGF w/low vaporizer settings; not seen with "open" system ventilation
Induction should be conducted w/(high/low) FGF. high
How does low FGF affect induction? Prolongs induction
What does overpressuring mean in regards to the concentration dial? Dial to max (i.e. 18% des)
Anesthetic "wash in" occurs with (high/low) FGF. low
Low flow maintenance is at _______ L/min. 1-2
What is the benefit of low FGF? Conserves heat, humidity, gas, and agent
Similar to utilizing low FGF, CO2 absorbers help conserve what three things? Agent, gas, humidity
At what flow levels is CO2 diluted to where there is little absorption and mostly scavenging? High flows 5-8L/min
Ionic reactions take place on the surface of what type of granules? soda lime
What can speed the efficiency of ionic reaction? 10-20% water content
What types of granules exhaust faster? dry granules
Identify two activators that can increase the speed of ionic reaction. NaOH, KOH
What do NaOH and KOH combine with and what does the reaction create? Combine with carbonate ions or CO2 to yield H20 and heat
How much energy is produced from the absorption of 1mol of CO2? 13,000 kcal
What dye is added to soda lime and how does it work? Ethyl violet; serves as pH indicator--at critical pH 10.3, changes from colorless to blue-purple
Sevoflurane in unstable in which CO2 absorbant? soda lime
Sevoflurane degrades into what toxic substance in soda lime? Compound A
What are the recommendations for sevo? Not recommended at TFGF <1L/min for more than 2Mac hours
What are the doses that are associated with death and renal injury in rats? 130-340ppm lethal; 25-50ppm renal injury
List in order, from greatest to lowest, the amount of carbon monoxide produced by the anesthetic gases. Des > Iso > Halo = Sevo
Which absorber has the greater propensity for Compound A production: Baralyme or soda lime? Baralyme
Compound A production is increased with (wet/dry) granules. dry
What are the recommendations for decreasing Compound A production? D/C O2 after surgery, regularly change absorbent, change absorbers if FGF is left on, use appropriate flows
How will using appropriate flows influence absorber granules? Tends to keep them moist
What feature prevents channeling in a CO2 absorber? Baffles
What does the gutter feature do in CO2 abosrbers? Collects moisture
What is the function of CO2 abosrbers? Neutralize CO2 from exhaled gas to give clean neutralized gas back to the patient
When stacked, which canister does most of the work to neutralize CO2? Top canister
What does CO2 react with when coming in contact with absorbers? Reacts with water impregnated on hygroscopic granules to yield carbonic acid (H2CO3)
What does the carbonic acid react with and what does it create? How does this benefit the patient? Reacts with a base to form a neutral salt -- exhaled gases are then inhaled w/o traces of CO2
What are the drawbacks to Baralyme? Flammable, degrades anesthetic agent and their efficiency
Baralyme (is/is not) available in the U.S. is not
What three bases does soda lime contain? Calcium hydroxide (94%), sodium hydroxide (5%), potassium hydroxide (1%)
What have strong bases been associated with? CO production and other toxins in the presence of desiccated absorbent
Which base does most of the work to neutralize CO2? Calcium hydroxide
What purpose to sodium and potassium hydroxide serve in CO2 absorbers? Accelerate the rate of reaction
How much water content is necessary to maintain speed and efficacy of the reaction? 10-20%
What are two functions of silica? Preserve granularity and prevent dust
What are the drawbacks to the neutralization of exhaled CO2? (3) 1)production of compound A 2)production of CO with strong bases 3)OR fires (Baralyme)
The CO2 absorbent reaction is an example of an (exo/endo)thermic reaction. Exo
True/False: Soda lime regenerates when it changes color from blue-violet to white. False-does not regenerate
What are the byproducts of combining carbonic acid and sodium hydroxide? soda ash (Na2CO3), water, energy
What is the first neutralization reaction? CO2 + H2O <-> H2CO3
What is the second neutralization reaction? Na2CO3 + Ca(OH)2 -> CaCO3 + NaOH
What occurs in the second neutralization reaction? Regeneration of the activator
Compound A is fatal over what levels? 130ppm
Compound A can result in renal injury at what levels? 25-50ppm
True/False: Compound A is produced only in desiccated CO2 absorbers. False - also in non-desiccated
True/False: Compound A production has been known to be lethal in humans. False
CO is produced with which absorber? Desiccated Baralyme
Besides Baralyme, where else has CO production been implicated? Desflurane with strong bases (NaOH and KOH)
Which absorbent has eliminated CO production? Amsorb Plus
Which gas is most susceptible to CO production? Desflurane w/desiccated granules
What are the recommendations for changing absorbents? (4) change regularly, change when the color indicates exhaustion, change all absorbers in a 2-canister system, change if the state of hydration is uncertain
What are early signs of CO2 absorber exhaustion? Increased partial pressure of end EtCO2 (possibly accompanied by increase in FiCO2); respiratory acidosis; hyperventilation; SNS activation; increased surgical bleeding; indicator color
What are signs of SNS activation? Flushed skin, cardiac irregularities, sweating
What are late signs of CO2 absorber exhaustion? Increased (and later decreased) HR and BP, dysrhythmias
Which two absorbers generally have higher levels of Ca(OH)2? Dragersorb 800 and Amsorb Plus
How many granules does ea. canister contain? 1kg of granules in approx. 1500ml of volume
How much CO2 is each 100g of granules able to absorb? 15L w/no channeling
What is the average adult CO2 production per hour? 15L
What is the expected lifespan of 1 canister w/total rebreathing?
How often should CO2 absorber canisters be changed? At least q48h
Channeling (increases/decreases) the efficiency of CO2 absorbers. Decreases
The Wall Effect creates a (high/low) level of resistance at the edge of the canister. low
Explain the process of channeling in a CO2 absorber. When channels are created, absorption capacity is exhausted before the rest of the canister is exhausted
Why should canisters be shaken? Settles the canisters and promotes uniform absorption
What are advantages of the circle system? Saves anesthetic agent, warms and humidifies gases, enhances scavenging, reduces pollution
What are disadvantages of the circle system? Costly, bulky, anesthetic levels change slowly d/t low flow, increased resistance to breathing from CO2 absorbers and 1-way valves, CO2 aborbers generate dust
What three things can inhaled dust lead to? Laryngospasm, bronchospasm, or PNA
Pressure should be released via the _______. APL valve
Release pressure via the APL valve serves what benefit? Reduces dust formation in the sytem
True/False: The circle system is always a closed system. False - can be used semi-closed
What are the advantages of a semi-closed system? Maintains anesthetic equilibrium, the system is full, excess gas escapes via scavenging, quick responses to changes in delivered parameters
A semi-closed system requires the use of more ______ and a properly operating _____ to reduce pollution. FGF; scavenger system
In what position is the APL valve when use the circle system as a closed system? Fully closed
What are advantages of closed systems? Less FGF and agent consumption
What are disadvantages of a closed system? System may be under or overfilled, rapid CO2 dessication, formation of compound A/methanol/formaldehyde/CO
An EtCO2 waveform without a return to baseline indicates what condition? Exhausted CO2 absorber
What do MAC numbers represent? Volumes (%) of end-tidal alveolar gas at atmosphere
How else can MAC numbers be expressed besides as a percentage? mmHg -- multiple MAC by 7.60 to get mmHg of each agent
In regards to agent delivery, anesthesia is dependent on ________ and not on _________. partial pressure; volume percentage
Created by: philip.truong