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NU 568
Exam 4 - CO2 Absorbers and Vaporizers
| Question | Answer |
|---|---|
| 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
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