Breathing System and Endotracheal Tubes Flashcards
What are the two types of patient breathing systems?
Re-breathing
Non-rebreathing
What are the two tubes for the rebreathing system?
Circle
Universal F
What are the tubes in the non-rebreathing system?
Mapleson A-F
Bain (Modified Mapleson D)
Mapleson F
Anatomic dead space
Airway structures that do not participate in gas exchange
Mechanical dead space
the portion of the anesthesia circuit where bidirectional flow is occurring (rebreathing of exhaled gases).
If excessive, this may cause an unsafe increase in inspired CO2
Capnograph adapter
the end of the endotracheal tube to sample gases
What are the components of a re-breathing system?
Fresh gas input and O2 flush Unidirectional valves Breathing hoses CO2 absorber Adjustable pressure limiting valve Reservoir bag
What are the advantages of the re-breathing system?
Lowe fresh gas flow rate required
Patient breathes warm, humidified gases
saves money
decreases environmental pollution
What are the disadvantages of the re-breathing system?
High resistance to breathing due to valves
Changes in anesthetic gas concentration occur slowly d/t lower fresh gas flow
More compnenets –> more potential for leaks
O2 Flush Valve
Bypasses vaporizer
Dilutes anesthetic gas in breathing system and reservoir bag
Delivers O2 directly to the breathing system at high pressure and flow
Adjustable pressure-limiting (APL)/pop-off valve
Limits pressure build up in breathing system
Pops off at 3-5 cmH2O
Carbon Dioxide absorber
Soda Lime
contains ethyl violet which changes color from white to purple when granules are exhausted
What are the signs of CO2 absorbent exhaustion?
Inspired CO2 is grater than 1-2mmHg on capnograph
Increased PaCO2 on blood gas
Calculation of bag size for small animals
15mL/kg x 6
What is the typical O2 flow rate for small animals (less than 50kg)?
Induction and recovery: 50-100mL/kg/min
Maintenance 20-50mL/kg/min
What is the typical O2 flow rate for large animals?
Induction and recovery = 20-50mL/kg/min
Maintenance = 10-20mL/kg/min
What are the components of the non-rebreathing system?
Fresh gas
Non-rebreathing tubes
APL valve (Bain) or open/close valve (Mapleson F)
Reservoir bag
What is not present in the non-rebreathing system?
Soda Lime canister
Unidirectional valves
What are the advantages of the non-rebreathing system?
Light, minimal dead space, minimal resistance to ventilation (use for small patients Less than 3 kg)
Concentration of anesthetic gas changes rapidly due to high fresh gas flow and small circuit volume
What are the disadvantages of the non-rebreathing system?
Patient breathes cold and dry gas due to lack of rebreathing
More expensive
Increases environmental pollution
What is important about Oxygen Flow rates in non-rebreathing systems?
Must be high as this is the mechanism for preventing rebreathing of CO2
Should be 2-3x tidal volume
Which monitor would help determine if the O2 flow rate was too low and patient was rebreathing CO2?
Capnograph
What is the advantage of Endotracheal tubes and intubation?
maintain patient airway Administer O2, deliver inhalant anesthetics Provide positive pressure ventilation Protect airway from foreign material Apply tracheal or bronchial suction
Routes of Intubation
Oral
Nasal
Tracheal
Pharyngotomy
What are the types of ET Tubes?
PVC, rubber or silicone
Cuffed or uncuffed
Cuff types
Murphy ET tube
can be cuffed or uncuffed
has a murphy eye that allows gas flow if end of tube is obstructed
Cole ET tube
Uncuffed
Used commonly in avian patients
has a “shoulder” that seals against the glottis
Wire-reinforced ET tube
Used to prevent collapse of tube lumen when patients are placed in extreme flexion (usually ophtho procedures)
Cannot use for MRI
Passive Scavenging Systems
Exhaust directly to atmosphere
F air canister
Active Scavenging Systems
Piped vacuum
F air canister
absorbs halogenated agents (anesthetic vapors)
does not scavenge N2O
