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59 Cards in this Set
- Front
- Back
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At peak inspiration, large gas flows are necessary:
___-____LPM child ___-____ LPM adult |
5-10 LPM child
30-60 LPM adult |
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At end exhalation, part of TV reamins in anatomical deadspace. This is the definition of what?
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Rebreathing
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What are two advantages of rebreathing?
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Reduces FGF
Conserves heat and humidity |
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No rebreathing if ____ > ____
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FGF > MV
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CO2 abosrber allows rebreathign of all gases except....
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CO2
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An open system is where an anesthetic is admin with ___ ___.
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Administered with ambient air (as vehicle that carreirs into lung)
Has access to atmosphere on inhalation and exhalation |
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Advantages of an open system include:
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Simple
Inexpensive Little reisistance to breathing |
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Can you control/assist ventilation w/an open system?
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No
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Disadvantages of an open system include:
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Lg amt of gas wated into atmosphere
Can't use impotent gases Cant control/assist vent Difficult to control level of anesthesia |
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Why is it hard to control level of anesthesia w/an open system?
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Patient lightens-->inc MV--> entrainment of RA to meet peak inspiratory demand -->dilutes anesthetic conc
"Light anesthesia begets light anesthesia" "Deep anesthesia begets deep anesthesia" |
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What are the three types of open systems?
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1. Open-drop
2. Insufflation 3. Ayres T-piece |
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Explain how an open-drop system works?
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Volatile anestheetic dropped onto 6-12 layers gauze stretched over wire frame
Liquid anesthetic vaporized at room temp, therefore pt breathes in vapor combined with RA |
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In an open-drop system, anesthetic conc depends on what 4 things?
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1. Size and fit of mask
2. MV 3. Ambient temp 4. Amt of liquid anesthetic on gauze |
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what happens if the temp decreases during an open-drop system?
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Temp of liquid/gauze dec--> vaporization decreased--> decreased inspired concentration
*condensation of water inc dead space and dilutes inspired conc also |
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How does insufflation work?
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Anesthetic gases delivered inton pharynx or larynx via nasal or oral catheter, ether hook, or mask held away from face
No rebreathign if FGF> 8-10LPM Drying of orotracheal mucosa Inc heat and water loss Useful for ped inductions |
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Ayres T-Piece is designed for use with an ____. How does it work?
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Use with an ETT
Anes gas enters via side tube, inspire a mix of anesthetic and RA Respirations controlled by occluding open end of main tube (danger of over-inflation) |
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With a SEMI-open system, it contains a _____, but no ____ ______ or ______. Access to atmos on ______ only
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Contains a reservoir
No CO2 absorber No rebreathing Exhalation only |
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What are some advantages of a semi-open system?
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Allows use of impotent agents
Assissted or controlled respirations Stable anesthetics Faster induction d/t N washout Used frequently in ped's |
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Disadvantages of a semi-open system?
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Inc amt of wated gas (bec inc FGF)
Inc heat and water loss Rebreathing with low FGF Valves inc resistance (if present) |
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Which setup (Mapelson D or F) has an adjustable valve at the BAG end? (This is what makes the two different)
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Mapelson F
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What are you inhaling with a Mapelson D?
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When FGF enters tubing on EXhalation it pushes dead space and alveolar gas out APL valve, so on INhalation you have a mix of gases from tubing and FGF.
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With a Mapelson D, do you have more rebreathing with a spontaneous slow RR or a spontaneous fast RR?
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Fast RR
Why: Fast RR (short expiratory pause)--not enough time to flush mixed gas from tubing-->rebreathing Slow RR (long expiratory pause)-->enough time for FGF to fill and flush mixed gas out. |
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If you do not want your pt to rebreathe on a Mapelson D system, what would you set their FGF to if they are spontaneously breathing?
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FGF = 2x MV
(100ml/kg in adults) (205 ml in children) |
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What should your FGF be on a Mapelson D with CONTROLLED respirations?
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70ml/kg/min adults
3.5LPM for kids 10-50kg 2LPM for kids <10kg |
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What is the purpose of a Bain Circuit with a Mapelson D?
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FGF-narrow tube that runs thru the corrugated tube.
INC heat and humidity retention |
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What is the problem with a Bain circuit?
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Unrecognized disconnection or obsturction fo inner tubing
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What is a Pethick Test?
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Checks patency of inner tubing with a Bain circuit
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How do you do a Pethick test?
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Close APL, occlude pt end and flush circuit w/O2 until reservoir bag is full. With O2 flush still on, open pt end, bag should COLLAPSE
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What happens during exhalation (SR or CR) with a Mapelson F system?
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dead space and alveolar gas enter tubing and mix with FGF.
FGF continues to enter and forces mixed gas into reservoir bag and out exhalation port |
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What FGF do you need with a Mapelson F to prevent rebreathing?
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2-3x MV to prevent rebreathing
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What is the most commonly used breathing system in the US?
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Semi-Closed Circle Absorber (SCCA)
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What are the components of a SCCA?
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1. Inspiratory AND expiratory corrugated tubing
2. Unidirectional insp and exp valves 3. CO2 absorber 4. Adjustable APL valve |
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How big is an adult reservoir bag? Child?
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Adult: 3L bag (35 cmH2O when quadrupled in size)
Child: 1.5L bag (30-50cm H2O when quadrupled in size) |
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What is the APL valve?
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Allows for variable pressure threshold for venting
Spring loaded valve varies the pressure in the breathing system. Contains check valve to prevent retrograde flow |
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What is the minimum opening pressure of the APL valve?
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1 cmH2O
Allows bag to fill before check valve opens |
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During inspiration (spontaneous or controlled), what does the check valve do?
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Check valve closes and gas flows to patient
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When is your APl fully open? Partially open?
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Fully during spontaneous resp
Partially during bagging or CPAP |
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What is the range of the APL valve?
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1-75cm H2O pressure in patient circuit
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What 3 things MUST be maintained to prevent rebreathing in a SCCA?
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1. Unidirectional valves needed
2. FGF can't enter circle between APL and patient 3. APL cannot be located between patient and inspiratory valve |
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What does a HEPA filter trap in the anesthesia machine?
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Traps 99.97% of 0.3 um particles:
--HIV: 0.08um --Hep C: 0.06um --Staph: 1.0um Can increase resistance CDC has NO recommendations regarding filters |
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4 advantages of a SCCA system:
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1. Relative constant inspired anes conc
2. Dec heat and water loss 3. Dec pollution 4. Lower FGF |
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4 DISadvantages of a SCCA system?
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1. Inc resistance to breathing
2. Bulky system, hard to clean 3. CO2 absorption depended upon freshness of sodalime 4. Approx 10 areas of disconnect |
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How does CO2 absorbent work? (Simple man's version)
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CO2 chemically combines w/H2O to for carbonic acid.
Hydroxide salts neutralize carbonic acid to heat, water and Ca++ Carbonate (and NaOH and KOH). |
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How is Amsorb different from Sodalime?
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Amsorb has IRREVERSIBLE color change once exhausted, and has no CO, Compound A or Formaldehyde production or degradation of anesthetic gases
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Why does CO2 absorbent change color?
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As NAOH is consumed and replaced with Ca(OH)2, pH falls and color chagnes from white to purple.
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How much does a CO2 canister absorb? When should it be changed?
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100gm absorbent can neutralize 26L before ETCO2 > 1%
BUT should change canister at 50% efficiency (15L absorbed) |
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CO2 canister should accomodate > ____ _____ TV
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One max TV
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How is compound A formed?
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Sodalime contains high amounts of KOH and NaOH--> react w/volatile anesthetics to form CO and cmpd A when SEVOFLURANE is broken down.
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What is cmpd A?
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Degradation product of Sevo.
Has dose dependent nephrotoxic effect on rats. |
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Have highest production of cmpd A with...
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Low FGF
KOH and NaOH absorbents Inc temp Long anesthetic duration Sevo conc and desiccation |
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What anesthetic agent produces the most CO?
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Des
(Followed by Enflurane>Isoflurane>Halothane) |
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What are some measures you can take to prevent CO formation in the anes machine?
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Turn off all gases at end of case
Turn off machine at end of day Use auxillary flowmeter for nasal/mask O2 Flush machines with 100% O2 on MONDAY mornings |
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With a double canister setup, what canister do you change out?
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Change top canister when color change reaches lower canister
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With a closed system, there is ____ access to atmos, and _____ _____ of exhaled gases
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No access to atmos
Complete rebreathing of exhaled gases |
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3 advantages of closed system:
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1. Low FGF
2. Minimum room pollution 3. Excellent heat and water conservation |
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2 disadvantages of a closed system:
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1. Greater risk of hypoxia and CO2 retention (if absorber full)
2. Rapid change in depth of anesthesia not possible (usually induction/extubation on SCCA system then changed over to closed) |
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Describe a closed circle system
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Same as SCCA w/APL fully closed and FGF 500-600ml/min
150-500ml will meet min O2 requriemetns and replace anesthetic |
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What is your FGF with "low flow anesthesia" in a closed system?
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FGF < MV (0.5-2 LPM)
APL closed/~fully closed Gas flow adjusted so reservoir bag refills (SR) or bellows reach bellows stop at end expiration |
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A disadvantage to low flow anesthesia is the accumulation of what?
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CO from smokers
Cmpd A |
