Anesthesia Delivery System Flashcards
How can CO2 be eliminated?
- washout with high flows of fresh gas
2. CO2 absorber
What are essential requirements in a breathing system. regarding
- gas delivery
- CO2
- dead space
- resistance
- deliver gases to alveoli in same concentration as set in shortest time
- eliminate CO2
- minimal dead space
- low resistance
What is the advantages to rebreathing of exhaled gases? What is a concern of rebreathing?
cheaper, adds humidification to gases but do not want to rebreathe CO2 - high FGF
What effect does dead space have on CO2?
dead space increases chance of rebreathing
How is gas delivered in an open system? What does this system not have? (3)
pt gets anesthetic gas plus gas in environment
no reservoir bag, no valves, no rebreathing
What are the 2 types of open systems? Give examples.
- insufflation - blow-by, tent, nasal cannula, steal induction
- open drop - ether mask (schimmelbusch) - historical, wire mask with cloth where anesthetic is dripped onto cloth and patient inhales
What are disadvantages of open systems?
no assist in ventilation
CO2/O2 accumulation under drapes
no control of anesthetic depth/FiO2
pollution
What is the “Steal” induction and is it a form of insufflation or open drop open system?
- approach pt with gas mask slowly as they inhale gas and environment
- insufflation system -
What are the 5 components of a semi-open system?
- facemask or ETT
- pop-off valve
- reservoir tubing
- fresh gas inlet
- reservoir bag
How do you prevent CO2 rebreathing in semi-open systems?
-with high fresh gas flows
How do you set the APL valve with spontaneous vs controlled ventilation?
- open with spontaneous breathing
- partially closed with controlled ventilation
What are examples of semi-open system?
Mapleson (A-F) - various configurations
Bain
Circle
What does CO2 rebreathing depend on?
- FG inflow rate
- minute ventilation
- spontaneous or controlled ventilation
What is the most efficient Mapleson model during controlled ventilation?
Where does FGF enter?
Where is the APL valve located?
What model is opposite of this?
- Mapleson D
- near facemask/patient
- opposite end
- Mapleson A
What should be the FGF for a Mapleson D with
- spontaneous respiration
- controlled ventilation
- FGF = 2-3 x MV
- FGF = 1-2 x MV
(MV = RR x TV, normal = 5L x 2 = 10 L of FGF)
Which model is a T-Piece?
What does it NOT have? (2)
What would be the FGF for spontaneous?
- Mapleson E
- no reservoir bag, no APL valve (no manual ventilation?)
- 2-3 x MV
Which Mapleson is popular in pediatrics?
- Mapleson F
- like Mapleson E (T-Piece) but has APL with reservoir bag
Which Mapleson is the Bain Circuit a modification of?
What is FGF for the Bain Circuit?
Is it used in spontaneous or controlled or both?
-Mapleson D
-same as Mapleson D
1. FGF = 2-3 x MV - spontaenous
2. FGF = 1-2 x MV - controlled
Both
What is a special feature in the Bain circuit FGF tubing?
What is the advantage to this?
What is the disadvantage of the Bain Circuit?
- FGF tubing is within corrugated/breathing tubing
- provide heat and humidity from exhaled gas to inspired gas
- potential for inner tube leaks, kinking, disconnect
Which Maples is the ambu bag a modified version of?
Can it deliver high FiO2?
Does it require FGF?
How do you refill the reservoir bag?
-Mapleson A with a non-rebreathing valve (only one with NR valve)
-yes.
-yes, dependent on MV
it is self-filling
What are 6 advantages of the Mapleson System?
- simple
- light
- provides positive pressure ventilation
- low resistance
- portable
- more predictable anesthetic concentration than open system and decreased pollution
What are disadvantages of Mapleson system?
- calculate FGF which varies per circuit and mode of ventilation
- anesthetic depth is variable
- possible CO2 buildup with rebreathing, low FGF
- FGF costly
- Special assembly
Which system does the anesthesia machine use?
What type of delivery system can it be used as?
What 2 things can adjust it into different systems?
- semi-closed Circle system
- semi-open, semi-closed, closed
- APL valve adjustment, FGF rates per system
What are 7 components of the circle system?
- FGF source
- insp/exp valves (unidirectional)
- insp/exp limbs/corrugated tubing
- y-piece connector
- adjustable APL
- reservoir bag
- CO2 absorber
What is the size of the reservoir bag neck?
22 mm (female connection to )
What is the reservoir bag made of?
neoprene or rubber
What is the function of the reservoir bag?
- accumulates expired gas
- assist/contrl ventilation
- visual/tactile monitor for observing spontaneous respiration
- protects from excessive pressure
What is the size/diameter of a T-Piece and an ETT?
T-piece = 22 mm male connection
patient end of ETT = 15 mm female connection
What is the purpose of an APL valve?
- releases gas to scavenge or atmosphere
- controls pressure in system
How should the APL be positioned with
- spontaneous resp
- assisted vent
- mechanical vent
- open or partially closed only if reservoir bag is able to collapse
- partially open
- closed (if machine does not have mode switch)
If unidirectional valves are working, where is dead space in the circle system?
between y piece and patient
What are 3 rules for a circle system arrangement?
- unidirectional valves must be between patient and reservoir bag on ins/exp limbs
- FGF cannot enter between exp valve and patient
- APL valve cannot be between patient and insp valve
When is a semi-open circle system used?
Not often, sometimes for sedation (with mask placed over face to increase FiO2)
In a semi-open circle system is there rebreathing?
How?
What position is APL valve?
Does it conserve heat/gas?
No. High FGF (10-15 L/min)
open
no
What is the most commonly used circle system? What flow rates does it use? Does it conserve heat/gas? Is there rebreathing? How is APL valve position?
- Semi-closed circle system
- Low FGF (1-3 L/min)
- conserves some heat/gas
- some re-breathing (minus Co2)
- partially closed and adjust as needed
When is closed circle system used?
How are flow rates?
Is there rebreathing?
What position is APL?
- third world countries
- FGF at minimal to match metabolic O2 needs
(i. e. 200 ml/min - O2 consumption calculation) - total rebreathing and conservation of all gases
- APL is closed
What is the formula for O2 consumption? (VO2)
10 x kg^(3/4)
What are advantages of the circle system?
- stability of inspired gas
- conserve moisture
- prevent pollution
- can be used for closed-system anesthesia
- can use low flows and no rebreathing of CO2
- scavenge wastes
What are disadvantages of circle system?
- complex, 10 connections (risk for leaks, obstr, disc)
- malpractice due to disconnects etc
- increased resistance
- less portable/convenient
