EQUIPMENT-Breathing circuits Flashcards
What are 4 classifications of breathing circuits
- Open
- Semi-open
- Semi-closed
- Closed
Describe the open breathing system
Example
- Does not allow for controlled ventilation
- Doesn’t permit delivery of precise inspired gas concentration
- Gas is exchanged with atm
Ex: nasal cannula, simple face mask, open drop
Describe the semi-open system
Example
- Contains gas reservoir
- No rebreathing of exhaled gases
Ex: Mapleson circuit, circle system (FGF > Vm)
Describe the semi-closed system
Example
- Contains gas reservoir
- Contains CO2 absorbent allowing patient to rebreathe
Ex: Circle system (FGF
Describe a closed system
Example
- Contains reservoir
- Contains CO2 absorbent
- Amount of gas added to circuit matches gas consumed by pt
Ex: Circle system (very low FGF, APL closed)
How does FGF and Vm determine the type of breathing circuit
If FGF is > Vm, it is semi-open
If FGF < Vm, it is semi-closed
What FGF determines a closed system
very low FGF with closed APL. This allows for 100% rebreathing
What are 5 advantages of the circle-system breathing circuit
- Consistent inspired gas concentration
- Maintains heat and humidity
- Low resistance
- Can be used as semi-open, semi-closed, or closed
- Minimizes OR pollution
What are 4 disadvantages of the circle-system breathing circuit
- Multiple places for disconnection
- Less portable than non-rebreathing circuits
- Unidirectional valve malfunction, stuck open (REBREATHING)
- Unidirectional valve malfunction, stuck closed (OBSTRUCTION)
What are the benefits of the reservoir bag
- Accumulated gas from exhalation is returned to pt during inhalation
- Visual and tactile monitor of pt ventilation
- Allows manual ventilation with positive pressure
- Bag is distensible and doesn’t exceed 60 cmH2O to decrease barotrauma
How does the reservoir bag conserve gas
It allows rebreathing and the use of low FGF, which uses less anesthetic gas
What is the purpose of the APL valve
It is an adjustable pressure-limiting valve determining how much pressure can be generated inside the breathing circuit during manual ventilation
Gas is diverted to scavenger when circuit exceeds the set APL pressure
Is the APL part of the vent system
No
The vent utilizes a spill valve to divert extra gas
Where does dead space begin when unidirectional valves are functioning properly
Begins at Y-piece
Ends at terminal bronchioles
What increases dead space in a breathing circuit
- Anything placed between the y-piece and the pt
2. Malfunction of the unidirectional valve
What is the purpose of unidirectional valves.
When is each valve open and closed throughout the respiratory cycle
Purpose = ensure gas moves in one direction
Inspiratory valve:
open = inspiration
closed = expiration
Expiratory valve:
open = expiration
closed = inspiration
How do unidirectional valves affect dead space of the breathing circuit
If a valve becomes incompetent, the corresponding limb is converted to dead space, allowing the pt to rebreathe exhaled CO2
Which limb of the breathing system becomes dead space is an inspiratory valve is stuck open
The inspiratory limb
Which limb of the breathing circuit becomes dead space if an expiratory valve is stuck open
The expiratory limb
Where is dead space in the breathing circuit if both unidirectional valves are stuck open
The entire circuit (both inspiratory and expiratory limb)
What is the pt at risk for with incompetent inspiratory or expiratory valves
Hypercarbia because pt is rebreathing exhaled CO2
Why should minute ventilation not be increased in the setting of failed CO2 absorber or incompetent valves
It will increase the amount of exhaled CO2 the pt rebreathes
What are 2 option if the CO2 absorbent exhausts during a procedure
- Convert a closed or semi-closed system into semi-open system by increasing FGF >Vm (>5-8 L/min)
- Change absorbent but know what to do if it doesn’t seat correctly
What are complications that can occur with an inspiratory valve that is stuck closed
Airway obstruction
What are 3 complications that can occur with an expiratory valve that is stuck closed
Airway obstruction
Breath stacking
Barotrauma
What are 2 causes of inspired CO2
- incompetent unidirectional valve (either one is stuck open)
- CO2 absorbent is exhausted
What are the 6 different Mapleson configuration
Mapleson A-F
Which mapleson circuit is the Jackson-Rees
Mapleson F
What types of circuits are Maplesons
Semi-open or non-rebreathing
What are 5 components of the Mapleson circuit
- Reservoir bag
- Fresh gas inlet
- Corrugated circuit tubing
- APL valve
- Mask
What 2 components are not present on a Mapleson circuit
- Unidirectional valve
2. CO2 absorber
What are the disadvantages of the Mapleson circuit
Allows rebreathing
Can lead to hypercarbia
Which Mapleson circuit does not have corrugated tubing
Mapleson C
Which Mapleson circuit does not have a reservoir bag
Mapleson E
Where is the fresh gas inlet located on each Mapleson A= B= C= D= E= F=
A= near bag
B - F = near pt
Where is the APL location on each Mapleson A= B= C= D= E= F=
A - C = near pt
D, E = Away from pt
F = none
Which Mapleson circuit does not have an APL valve
Mapleson F
How is rebreathing minimized in Mapleson circuits
- Use of high FGF to washout exhaled gases
What is the drawback to the Mapleson A
FGF >20 L/min required with controlled ventilation
Which Mapleson circuits are best for spontaneous ventilation
A > DEF > CB
Which Mapleson circuit is worst for spontaneous ventilation
B
Which Mapleson circuit is best for controlled ventilation
D-FE > BC > A
Which Mapleson circuit is worst for controlled ventilation and why
A
Because a FGF > 20 L/min is required to prevent rebreathing
The Bain system is which modified Mapleson circuit
D
How does fresh gas flow through the Bain circuit
Enters through the thin inner tubing
Exits through the outer corrugated tubing
What flow should the Bain circuit be set to prevent rebreathing
FGF should be 2.5x Vm
What test is performed to ensure the Bain circuit is functional
The Pethick test
- Occlude elbow of circuit
- Close APL valve
- Flush O2 to fill circuit
- Remove occlusion while flushing circuit
How is the incoming fresh gas warmed in the Bain circuit
By the exhaled gas
