Breathing circuits Flashcards
No rebreathing and no reservoir is considered
an open circuit
No rebreathing with a reservoir is considered
a semi-open
Partial rebreathing with a reservoir is considered
a semi-closed
Complete rebreathing with a reservoir is considered
a closed
Breathing circuits are classified into four types:
open
semi-open
semi-closed
closed
Open breathing systems do not allow for
controlled ventilation, nor do they permit the delivery of precise inspired gas concentrations
Examples of open breathing systems include
nasal cannula
insufflation
simple face mask
open drop
Examples of a semi open system include
mapleson circuit (FGF dependent on design)
circle system (FGF> minute ventilation)
Examples of a semi closed system include
circle system (FGF <minute ventilation)
Examples of a closed system include
circle system with very low FGF and APL closed
Advantages of the circle system include
less OR pollution
maintenance of heat and humidity of the inspired gas
precise control of inhaled gas concentrations
The circle system can be configured in three ways:
semi open: FGF> minute ventilation
semi-closed: FGF < minute ventilation
Closed: FGF only replaces gas consumed by the patient (APL is closed)
_______________ determines how much gas remains in the circuit and how much gas is directed to the scavenger
An adjusting pressure limiting valve (APL)
The circle system contains ________________________ that ensure fresh gas travels in one direction.
two unidirectional valves (one in the inspiratory limb and one in the expiratory limb)
Malfunction of either unidirectional valve converts the region between the y-piece and the affected valve to
apparatus dead space (risk of hypercarbia)
The most common circle system-related causes of rebreathing include an
incompetent unidirectional valve
exhausted CO2 absorbent
If a unidirectional valve is stuck open, we will see
rebreathing
If a unidirectional valve is stuck closed, we will see
airway obstruction
Disadvantages of the circle system include
multiple places where disconnection can occur
less portable than non-rebreathing circuits
unidirectional valves can malfunction
The reservoir bag provides the following benefits during controlled and assisted ventilation:
exhaled gas accumulates inside the bag during exhalation and is returned to the patient on the next inhalation- permits rebreathing and the use of lower fresh gas flows
bag functions as a visual and tactile monitor when patient is spontaneous
allows you to generate positive pressure to deliver assisted or controlled ventilation
most distensible component of the breathing system
ASTM requires that the pressure inside an adult-size reservoir bag does not exceed an internal pressure of
60 cmH2O if the bag is inflated up to 4 times its size
When the unidirectional valves are working properly, dead space begins at
the y-piece and ends at the terminal bronchioles of the patient’s lungs
The inspiratory valve is open during
inspiration and closed during expiration
The expiratory valve is closed during
inspiration and open during expiration
The definitive fix for an incompetent unidirectional valve is to
correct the valve; if this cannot be done then a closed or semi-closed system should be converted to a semi-open system
What is the BEST Mapleson circuit for a spontaneously ventilating patient?
A. A
B. B.
C. C.
D. D.
Mapleson A
What are the types of Mapleson circuits?
A, B, C, D, E, & F
All Mapleson designs are _____________________ circuits
semi-open (non-rebreathing)
With Mapleson circuits, since inhaled and exhaled gases travel through the same tubing, there’s a risk of
rebreathing
What Mapleson design is the worst for spontaneous ventilation?
Mapleson B
What Mapleson design is the best for controlled ventilation?
Mapleson D
What Mapleson design is the worst for controlled ventilation?
Mapleson A
What components are present in Mapleson circuits?
reservoir bag
fresh gas inlet
corrugated circuit tubing
APL valve
Mask
(Mapleson E does not contain an APL valve or reservoir bag)
What components are not present in Mapleson circuits?
CO2 absorber
unidirectional valves
Describe the Mapleson A circuit?
Fresh gas inlet–>bag–>APL valve–>Mask
Describe the Mapleson B circuit.
bag–> fresh gas inlet–> APL valve–> mask
Describe the Mapleson C circuit.
Bag–> fresh gas inlet–> APL valve–> mask
same as Mapleson B but no corrugated tubing
Describe the Mapleson D circuit.
Bag–> APL valve–> fresh gas inlet–> mask
Describe the Mapleson E circuit.
corrugated tubing–> fresh gas inlet–> mask
Describe the Mapleson F circuit.
APL valve–> bag–> fresh gas inlet–> mask
During expiration, gas containing carbon dioxide
enters the corrugated tubing and travels away from the patient
With Mapleson circuits, rebreathing is minimized with
higher FGF, smaller tidal volume, and longer expiratory time
What are advantages to the Mapleson circuit?
less airway resistance (good for peds)
convenient
easily scavenged (varies by type of circuit)
Bain circuit prevents heat loss
Disadvantages to the Mapleson circuit include
increased apparatus dead space
requires high FGF to prevent rebreathing
loss of heat and humidity
inefficient use of inhaled anesthetics
risk of environmental pollution
unrecognized kinking of fresh gas hose in Bain circuit
Maples A requires a FGF of __________ during controlled ventilation
~20 L/min.
