Breathing Systems Pt. 2 (Exam II) Flashcards
What components are missing from a Mapleson circuit?
- CO₂ absorber
- Unidirectional valve
- Separate Ins & Exp limbs
Which system has the best efficiency for spontaneous ventilation?
Mapleson A (Magill’s System)
Which system has the worst efficiency for controlled ventilation?
Mapleson A (Magill’s System)
Rebreathing with a Mapleson A during a controlled ventilation situation occurs unless what?
Unless minute ventilation if very higher (>20 L/min)
How is rebreathing prevented during spontaneous ventilation with a Magill’s system?
FGF must be greater than (or equal to) minute volume.
FGF should be 2x minute volume during spontaneous and controlled ventilation to prevent rebreathing in a _________ system.
Mapleson B
System is obsolete
How does a Mapleson C circuit differ from a Mapleson B?
Mapleson C excludes corrugated tubing found on Mapleson B.
What circuit is used for emergency resuscitation?
Mapleson C
What FGF characterized a Mapleson C circuit?
2x minute volume.
What breathing circuit is most efficient for controlled ventilation?
Mapleson D
What is the Bain modification?
What breathing circuit is it used on?
Inspiratory gas targeted through an inner tube. Expiratory gasses exhaled into the outer corrugated tubing.
Used on a Mapleson D
What FGF is used with a Mapleson D system?
2 - 2.5 x minute ventilation
Which circuit has no reservoir bag or APL valve?
No capability to ventilate the patient manually
Mapleson E
Which circuit is used in spontaneously breathing patients to deliver O₂ ?
Mapleson E
What is another name for a Mapleson E circuit?
Ayre’s T-Piece
A Jackson Rees is a modified ___________ circuit, where a reservoir bag is added to the circuit.
Mapleson E
Mapleson E + Jackson Rees = Mapleson F
How is excessive pressure prevented with a Mapleson F circuit?
No APL valve present
List all the Mapleson Circuits in terms of most efficient to least efficient for spontaneous ventilation.
A > DFE > CB
List all the Mapleson Circuits in terms of most efficient to least efficient for controlled ventilation.
DFE > CB > A
What are the advantages of Mapleson Circuits?
- Simple, inexpensive, lightweight
- Low resistance to gas flow
- No toxic products d/t CO₂ absorbent
- No degradation of VAA’s
What are the disadvantages of Mapleson circuits?
- Require high FGF
- Can’t conserve heat & humidity
- Scavenging difficult (except D)
- Not suitable for MH patients (cant increase FGF to remove CO₂)
Extent of rebreathing and conservation of exhaled gasses in a circle system depends on _____.
FGF
In a circle system, higher FGF = less _________ and more ______ ____.
rebreathing; waste gas
How is rebreathing prevented in a circle system?
- Unidirectional valves located between patient & reservoir bag
- FGF cannot enter circuit between exp valve & patient
- APL valve cannot be located between patient & inspiratory valve.
What characteristics define a semi-closed circle system?
- Low-flow anesthesia
- FGF < minute ventilation
- 50% of expired gas is rebreathed after CO₂ removal
In what patients would a semi-open circle system be used?
Why?
- post-op & ICU vents, scuba
- Higher FGF w/ minimal rebreathing and more venting of waste gasses.
What are the characteristics of a closed circle system?
- Complete rebreathing
- No waste gas vented
- O₂ matches metabolic demand
- Minimal flow anesthesia
- VAAs are added in precise amounts
What are the advantages of Low-flow anesthesia?
- Decreased VAA usage
- Better temp & humidity control
- Reduced environmental pollution
What are the disadvantages of low-flow anesthesia?
- Difficulty adjusting depth quickly
- Possible accumulation of gasses (CO, acetone, methane, etc)
- VAA degradation products
What are the advantages of a circle system?
- Low FGF can be used
- CO₂ elimination
- Conserves heat/moisture/etc.
- OR pollution prevention
- stable inspired gas concentration
What are the disadvantages to a circle system?
- Complex design
- CO or compound A
- Compromised VT during controlled ventilation
What are the use cases for self-inflating manual resuscitators?
- Pt transport
- CPR
- Emergency backup
- hand ventilation in absence of O₂ or medical air
What are hazards associated with self-inflating manual resuscitators?
- Barotrauma
- Gastric insufflation
- Large variation in VT, PIP, and PEEP
- non-rebreathing valves generate resistance
Where are bacterial filters placed on the breathing system?
Expiratory limb
What are the two types of bacterial filters?
- Small pore (↑ resistance, pleated for ↑ surface area)
- Large pore ( ↓ resistance, smaller surface area)
Where would a combination bacterial filter (filter + HME) be placed?
At the Y-piece (inspiratory and expiratory barrier)
What are some of the complications of bacterial filters?
- Obstruction (sputum, edema fluid, etc)
- Leakage
At what point in the airway is heating and humidification of air complete?
Mid-Trachea
Cool inspired gas may trigger ________.
Bronchospasm
Absolute humidity occurs at _____ mg/L (100% relative humidity).
44 mg/L
What can occur with underhumidification of air?
- Resp Tract damage
- Body heat loss
- Tracheal tube obstruction (thickened secretions)
What are HMEs?
Where are they placed?
- Heat and Moisture Exchanger
- Placed between Y-piece and proximal end of ETT
What are some disadvantages with use of an HME?
- Lower EtCO₂ reading
- ↑ resistance & circuit dead space
- Reduced efficiency w/ large VT
What are the advantages of active humidifiers?
- Can deliver gas at body temp or even higher
- More effective than HME’s
What are the disadvantages of active humidifiers?
- Bulky
- Contamination (hard to clean)
- Expensive (compared to HME)
- Electrical problems/ thermal injury potential
- Water aspiration risk
Extent of rebreathing and conservation of exhaled gasses in a circle system depends on _____.
FGF
