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