Breathing Circuit Flashcards
Mapleson A
- No rebreathing if FGF> alveolar ventilation
- APL valve opens during expiration so can’t truly ventilate someone
What is the minimum alveolar ventilation?
250 ml/ min
What is the characteristic of a Mapleson A
where is the APL valve?
what type of tubing?
where is the FGF?
APL valve : near the patient
corrugated tubing
FGF into the reservoir bag
** most efficient for Co2 elimination during spontaneous breathing
Characteristic of Mapleson B
where are the FGF and APL?
- Characterized by FGF and APL valve closer together near patient to reduce rebreathing
- Less efficient than Mapleson A during SV 2* mixture of gases and FGF required
- Can be used with any mode of ventilation
- Requires 2X minute ventilation of FGF to prevent rebreathing Uncommon to use today
Characteristics of Mapleson C
- Much like Mapleson B but with shortened expiratory limb
- Because of this, the inhaled gases contain more alveolar gas and so the FGF must be at least 2X minute ventilation to prevent rebreathing
- Not efficient or economical
- Can be used with any mode of ventilation; was used for resuscitation
Mapleson D characteristics
where are the FGF and APL valve?
How much FGF does it require?
same as Mapleson D
but they switched the position of FGF and APL
- Resembles Mapleson A except the locations of the FGF and APL valve are reversed
- Placement of FGF near patient provides efficient CO2 elimination, regardless of mode of ventilation
- Requires FGF to be 2X minute ventilation to prevent rebreathing
What is special about the Bain Circuit?
Version of Mapleson D: BAIN CIRCUIT
- FGF enters through narrow tube within corrugated expiratory limb
Advantages:
- Warming of FGF by surrounding exhaled gases in expiratory limb
- Improved humidification 2* partial rebreathing
- Ease of scavenging waste gas from APL valve (actually converts this to semi-closed system)
- Disposable; easy to sterilize; lightweight
Disadvantages:
- Increased resistance to breathing
- Rebreathing of exhaled gases due to unrecognized inner tube disconnection
- Absence of FGF due to unrecognized kinking of inner tube
Mapleson E
characteristics
- Consists of expiratory limb connected to Ayre’s T-piece
- Ayre’s T-piece: metal tube with an internal diameter of 1 cm that receives FGF from a sidearm
- Has no reservoir bag but can manually ventilate by intermittent occlusion of the expiratory limb that forces gas into the patient
- Requires FGF 3X minute ventilation to prevent hypercarbia
Not commonly used
Bain Circuit how much FGF is needed during controlled ventilation?
How about during spontaneous ventilation?
During CV –> requires FGF rate equal to ~70-100ml/kg to prevent hypercarbia
During SV –> requires FGF rates up to 100-300ml/kg to prevent hypercarbia because patient may not be able to sufficiently increase alveolar ventilation in the presence of anesthetic induced depression of ventilation
JACKSON-REES: MAPLESON F
(MODIFIED AYRE’S T-PIECE)
characteristics
- Addition of reservoir bag with APL valve to expiratory limb of Mapleson E
Advantages:
- Ease of instituting CV and able to monitor ventilation during SV by movement of reservoir bag
- Able to scavenge gases
- Can use with any mode of ventilation
Pediatric usage (< 25 kg)
- Minimal dead space
- Low resistance to breathing
Disadvantage:
- Requires FGF 2-3 X minute ventilation to prevent hypercarbia with at least 4 L O2
Arrange breathing circuits according to which is better for CV
D/F>B>C>A
[Dead Bodies Can’t Argue]
Arrange breathing circuits according to which is better for SV
A>D/F>C>B
[All Dogs _C_an Bite]
In a circle system, how long is the tubing? what can of tubing is it?
how much is the reserve volume of the reservoir bag?
- Corrugated tubing in inspiratory and expiratory limbs are 22 mm, which provides minimal resistance to breathing and prevent kinking
- Gas reservoir bag has reserve volume of 60 L/min, which exceeds conventional FGF ~3 L/min
- APL valve allows adjustment of pressure
