Anesthesia Systems Flashcards
3 Essential Components of a Breathing Circuit
Low resistance conduit for gas flow
Reservoir for Gas that meets inspiratory flow demand
Expiratory port or valve to vent excess gas
Requirements of a Breathing System (5)
- Deliver the gases from the machine or device to the alveoli in the same concentration as set and in the shortest possible time
- Effectively eliminate carbon dioxide
- Minimal apparatus dead space
- Low resistance to gas flow
- Allow rapid adjustment in gas concentration and flow rate
Effects of hypercarbia
Right shift on oxygen-hemoglobin dissociation curve
- Acidosis
- Vasodilation -> hypotension
- tachycardia
- increased ICP
The anatomic dead space in the circle system begins at
The Y Piece
Desirable Features in a Breathing System (8)
- Economy of fresh gas
- conservation of heat
- adequate humidification
- light weight
- convenience during use
- efficiency during spontaneous and controlled ventilation
- adaptability for adults, children, and mechanical ventilators
- proviso to reduce environmental pollution - safe disposal of waste gas
Higher FGF is associated with
less rebreathing in any circuit
Dead space increases
The chance of rebreathing CO2
Apparatus Dead space ends where
The inspiratory and expiratory gas streams diverge (Y-piece)
Apparatus dead space can be minimized by
separating the inspiratory and expiratory streams as close to the patient as possible (hence Y piece)
The concentration of inspired gas most closely resembles that delivered from the common gas outlet when
rebreathing is minimal or absent
Open classification =
no reservoir, no rebreathing (NO VALVES)
ex. sufflation, blow by, tenting, bronchoscopy port, nasal canula
Semi-Open classification =
Reservoir, no breathing
ex. some Maplesons, FGF dependent.
circle systems if FGF > MV (i.e. no rebreathing)
Semi-Closed classification =
Reservoir, partial rebreathing
Circle systems, FGF < MV
Closed classification =
Reservoir, complete rebreathing
FGF is minimal, APL closed.
Advantages of open systems
(i.e. blow-by, insufflation) - 7
Simple! Avoids direct patient contact No rebreathing of CO2 No reservoir bag No valves so less resistance and no chance of disconnection Good for peds Good for facial surgery
Disadvantages of Open Systems (blow-by, insufflation) - 5
No ability to assist or control ventilation
Requires high FGF to eliminate CO2 (especially with drapes/tenting)
No control of anesthetic depth/Fio2
Environmental pollution
Increased Fire Risk
Mapleson Components (4)
Connection point to a facemask or ETT
Reservoir Tubing
Fresh Gas inflow tubing
Expiratory pop-off valve / port
Best Measure of optimal FGF to prevent re-breathing
End tidal CO2
Fundamental ways that maplesons differ from circle systems
Bidirectional flow
Lack of CO2 absorber, elimination is dependent on FGF
Instances when maplesons are used - 5
Pediatrics
Transportation of patients
Procedural sedation
Weaning tracheal intubation
pre oxygenation during out of OR management
Three distinct functional groups of maplesons
A
BC
DEF
Structure of Mapleson A (Magill)
FGF is after reservoir bag,
Pop off valve is near face mask/ETT
FGF and pop valve are opposite each other
Best mapleson for Spontaneous Ventilation
All > Dogs > Can > Bite
With Mapleson A during Spontaneous Ventilation:
FGF = 1x MV then
there is no rebreathing