I. Anesthesia Breathing Circuit Flashcards
What are the two main goals of the anesthesia breathing circuit?
- Deliver oxygen and anesthetic gases.
- Eliminate carbon dioxide ( either by wash out with adequate fresh gas flow or by absorption)
The volume of gas inspired or expired with each respiratory cycle.
Tidal volume (Vt)
Tidal Volume is measured as the amount of air inspired or the amount of air expired (depending on the configuration of the anesthesia machine – it is not a measure of both (combined amount).
During normal breathing, inspiration should roughly equal the volume of expiration.
What is the normal tidal volume (ml/kg/breath)?
6-8 ml/kg/breath
Breaths per minute
Respiratory rate
What is the normal respiratory rate?
12-16 breaths/min
Total volume of gas entering/leaving lungs per minute
Minute ventilation
How do you calculate minute ventilation (Ve)?
Ve = Vt x RR
What is the normal minute ventilation??
70-100 ml/kg/min
Volume of breath that does not participate in gas exchange (ventilation without perfusion)
Dead space (Vd)
Vd/Vt = _____
1/3 tidal volume
What is it called when some expired alveolar gas (containing ____ CO2) is inspired in the next tidal volume?
- Rebreathing
- 5%
What are a few variables that affect rebreathing?
- Circuit design
- FGF rate
- Scavenging
What is the main reason we would want to mitigate rebreathing?
In order to disallow carbon dioxide levels in the blood from increasing
Resistance to flow can be minimized by:
- Reduction in circuit length.
- Increase circuit diameter.
- Avoid Sharpe bends in circuit.
- Eliminate unnecessary valves.
- Maintain laminar flow. 
What are two main breathing circuit design considerations intended to ensure the patient breathes in a satisfactory way?
- Decrease the work of breathing
- Decrease physiological dead space
What classification of anesthetic breathing systems is employed on modern anesthesia machines??
Semi closed
What are the four different classifications of anesthetic breathing systems??
- Open.
- Semiopen.
- Semi closed
- Closed
Which anesthetic breathing system is subdivided into various Mapleson systems?
Semiopen
How many unidirectional valves are featured on the semi closed system?
Name them.
3
APL, Inspiratory, Expiratory
Which breathing circuit has virtually no connection between the breathing circuit and the patient’s airway?
Open circuit
Nasal cannula, open drop ether, and insufflation are all examples of what type of circuit?
Open circuit
An open circuit has no:
Rebreathing
Scavenging (No unidirectional valves)
Reservoir
Neutralization of CO2
A nonrebreather circuit is what type of circuit?
Semi-open
Semi-open breathing systems feature what characteristics?
- No neutralization of CO2
- No rebreathing BUT requires high fresh gas flow
- Work of Breathing is Low because there are no unidirectional valves or absorption canisters that can increase resistance
- May have an APL valve
- May have a gas reservoir bag
What are the 5 basic components of the Mapleson breathing circuit?
- Facemask.
- Reservoir bag.
- Corrugated tube.
- Fresh gas, flow inlet.
- Expiratory valve or adjustable pressure limiting (APL) valve
What Mapleson component stores fresh gas flow for following inspiration?
Reservoir bag
Apart from fresh gas storage, what are two other uses for the Reservoir bag?
- Acts as a monitor of patients ventilation.
- Used to assist or control ventilation
What Mapleson component connects the components of the circuit to the patient, and can also act as an additional reservoir for gases?
Corrugated tube (b/w facemask and Reservoir bag)
In terms of length and diameter, what would allow a corrugated tube to have the most optimal gas flow?
Increased diameter
Shortened length
One-way adjustable, spring-loaded valve that allows gases to escape when the pressure exceeds a set limit.
Expiratory or APL valve
What Mapleson System s good fro spontaneous breathing patients due to its low resistance?
Mapleson A
Hint: spontAneous breathing
has low minimum FGF rate to eliminate rebreathing
2 Modifications of A: Magill & Lack
What is an inconvenience of the Mapleson A circuit?
Pressure relief valve is located inconveniently close to the patient
Fresh gas inlet is near the reservoir bag
What two systems require FGF of 2x the minute ventilation in order to eliminate rebreathing, thus making these systems obsolete?
Mapleson B & C
*However, these systems are frequently used all over the hospital for emergency resuscitation and/or manual ventilation**
What is the major advantage to the Mapleson C system?
It is very light and Compact
Ambu bag
What type of system is the Ambu bag?
Mapleson C
Which system is also known as the Bain system?
Mapleson D
Which system has an inner tube for FGF, while the exhaled gas exits through the corrugated outer tube?
Mapleson D (Bain)
What are the major disadvantages of the Mapleson D?
- Inefficient for SPONTANEOUS VENTILATION Requires FGF 3x Ve
- Unrecognized O2 disconnects
- Kinking of inner FGF tube
- Not easily converted to portable
Hint: NUKI
What are the advantages of the Mapleson D?
- Efficient for CONTROLLED VENTILATION (only requires FGF 1x Ve)
- FGF warmed by surrounding exhaled gases
- Improved humidification with partial rebreathing
- Ease of scavenging waste gases
- Easily accessible APL valve
- Disposable/sterile
What is the major difference in the Mapleson E & F systems compared to others?
They are valveless
In the Mapleson ____ system, tubing is added to the expiratory circuit which effectively becomes the FG reservoir during inspiration.
E
The Mapleson F is a modification of the E system, but with what major addition?
A reservoir bag
Allows us to observe ventilation during SV as well as controlled ventilation & support breathing
What are the 2 major disadvantages of both the E & F systems?
- Poor waste gas removal (requires high FGF 3x Ve)
- Poor humidification preservation
What anesthesia niche do the E & F systems accommodate?
Popular with pediatrics (Mostly F system: Jackson-Rees Modification)
Easy to assemble, Inexpensive, LOW RESISTANCE (NO VALVES)
Mapleson ____ has the FGF inlet and APL valve near the facemask.
Mapleson B
Mapleson ____ features the APL valve near the reservoir bag.
Mapleson D
Mapleson _____ has no APL valve or reservoir bag.
Mapleson E
Which system has an open ended Reservoir bag but no APL valve?
Maplson F
Efficiency in spontaneous ventilation Mnemonic:
All Dogs Can Bite
A>DFE>CB
Efficiency and controlled ventilation mnemonic:
Dog Bites Can Ache
DFE>BC>A
What circuit as EFFECTIVE for both controlled and spontaneous ventilation?
Mapleson D
What system is used for resuscitation with manual ventilation because they are small and light weight (no corrugated tubing)?
Mapleson C
Which circuit issues for both the spontaneous and controlled ventilation in pediatric patients?
Jackson-Rees (F)
Hey circle system can be what three types of circuits, depending on the amount of fresh gas flow?
- Semi open.
- Semi closed.
- Closed.
Which type of system is associated with partial rebreathing of gases with moderate fresh gas flow?
Semi-closed
Which system is associated with total rebreathing of exhaled gases with low fresh gas flow?
Closed system
Which breathing system has a low fresh gas flow requirement, and therefore requires the carbon dioxide to be mostly absorbed, leading to frequently, exhausted absorbent.
Closed breathing circuit
- this type of circle system is not utilized in current practice, however, it’s basic function can be mimicked with modern machines*
Characteristics of the closed breathing system
- Always has a gas reservoir bag
- Total rebreathing of exhaled gases
- provides for chemical neutralization of carbon dioxide
- absorbent exhausted quickly due to low fresh gas flow*
- Fresh gas flow requirement is much less than Ve
- contains three unidirectional valves
- work of breathing is higher than open or semi-open systems
Characteristics of the semi closed breathing system
- Partial rebreathing of exhaled gases
- Provides for a chemical neutralization of carbon dioxide
- Fresh gas flow requirement is less than Ve (moderate fresh gas flow)
- contains three unidirectional valves
- work of breathing is higher than open or semi open systems*
Advantages of the circle breathing system
- Stability of inspired gas concentrations
- Conservation of respiratory moisture and Heat
- Prevention of operating room Pollution
- Can be used for all Ages
- Closed system or low flow possible
- Low Resistance
SHARP Circle
Disadvantages of the circle breathing system
- Complex design
- Increased dead space (normal = .33/ intubated = .46/ mask = .65)
- malfunctions of unidirectional valves are possible
What are the six components of the circle system?
- Fresh gas Inlet (B/w absorber & inspiratory valves)
- Unidirectional check valves. (Close to pt in both the inspiratory and expiratory limbs)
- APL valves (before absorber)
- Reservoir bag (in expiratory limb)
- CO2 absorbent Canister. (B/w inspiratory and expiratory limbs)
6 . Y-Piece connector 
I Ate CURY
what component conserves absroption capacity and minimizes loss of fresh gas?
component of the circle system
APL Valve
what are two ways that CO2 absorbants minimize waste?
- Allows reduction of fresh gas flow (w/o absorbant, FGF would have to be ↑)
- Allows exhaled anesthetic agents to get rebreathed (circulate back through the system)
3 types of CO2 absorbant
- Soda Lime (Sodium hydroxide)
- Baralyme (Barium hydroxide)
- Amsorb Plus (Ca Chloride)
Baralyme removed from market in 2005 due to fire/explosion risk
What are the two types of dead space?
- Anatomical Dead Space: this relates to the volume of air that remains in the airways after completion of an inspiration, and does not reach the alveoli for oxygen exchange. Approximately 1/3 of each inspiration remains in anatomical dead space (trachea, bronchi, & bronchioles).
- Physiological Dead Space: air reaches the alveoli, but due to abnormality, oxygen is unable to be exchanged. There could little/no perfusion or other lung disease or condition (embolism).
Mapleson Circuits Image
Mapleson Circuit Mnemonic
A: APL near pt.
B/C: “Both Combined” - APL & FGF near pt
(C: Corrugated tube absent)
D: Distant APL away from patient
(FGF still neat pt)
E: “Everything Absent” No APL/No Bag
(FGF still near pt)
F: “Free-Flow” No APL valve
All Mapleson circuits have this one thing in common?
FGF inlet
Mapleson E & F both are missing what?
No APL
All mapleson circuits have a reservoir bag except?
Mapleson E
Halothane color
Red
Enflurane color
Orange
