Breathing Systems Flashcards
Two types of breathing systems
Rebreathing
Non-rebreathing
Rebreathing tube types
- Circle/Y piece
2. Universal F
Non-rebreathing tube types
- Mapleson D
- Mapleson F
- Bain
Components of the Rebreathing system
- Fresh gas and O2 flush
- Unidirectional valves (inspiratory and expiratory)
- Breathing hoses
- CO2 absorber
- Adjustable pressure limiting valve aka pop-off valve
- Reservoir bag
Rebreathing system advantages
- Lower fresh gas flow rate
- Saves money
- Decreases pollution
- Patient breathes warm humidified air
Rebreathing system disadvantages
- More components and potential for leaks
2. Increased resistance for smaller patients (
Pop-off valve
Limits pressure buildup in the system
Position of the pop-off valve
ALWAYS OPEN
Unless checking for leaks or administering positive pressure ventilation
Consequences of leaving the pop-off valve closed
Increases pressure in breathing system
Results in possible cardiopulmonary injury
Breathing system pressure gauge
SHOULD ALWAYS BE ZERO
Except: performing leak checks or providing positive pressure ventilation
Most common CO2 absorber medium
Soda lime
Calcium hydroxide with small amounts of sodium hydroxide and crystal violet (colour indicator)
Colour change in soda lime
White- fresh
Violet- exhausted
Signs of exhaustion
- Increase in tidal CO2
- Increased ventilation, HR/BP (then drop) if light enough
- Rebreathing capnograph
- Respiratory acidosis
- Red mucous membranes due to carbon monoxide production/inhalation
Reservoir bag function
Observe ventilation, inspiratory reserve, administer manual positive pressure ventilation
Calculation for reservoir bag size
Tidal volume = 10-20mL/kg x 6
Round UP if between sizes
Oxygen flow rate-
Rebreathing Small animal
Induction/ Recovery= 50-100 mL/kg/min O2
Maintenance= 20-50mL/kg/min O2
Oxygen flow rate
Rebreathing Large animal
Induction/ Recovery= 20-50 mL/kg/min O2
Maintenance= 10-20mL/kg/min O2
Non-rebreathing system components
- Fresh gas
- Non-rebreathing tubes
- APL (mapleson D) or open/close (mapleson F) valve
- Reservoir bag
Non-rebreathing Advantages
- Very light with minimal dead space
2. Minimal resistance to ventilation (better for
Non-rebreathing Disadvantages
- High Gas flow rate
- More expensive to run larger patients
- Increased environmental pollution
- Gas cold and dry
Non-rebreathing Oxygen flow rates
2-3x tidal volume in most cases
200-300mL/kg/min O2
Indications for endotracheal intubation
- Maintain patent airway
- Protect airway from foreign material
- Provide intermittent positive pressure ventilation (IPPV)
- Apply tracheal or bronchial suction
- Administer oxygen
- Deliver inhalant anesthesia
Benefits of intubation
- Reduced anatomical deadspace
2. Maintain inhalant anesthesia with minimal environmental contamination (with properly inflated cuff)
Routes of Intubation
- Oral
- Nasal
- External pharyngotomy
- Tracheostomy
E-tube materials
PVC, rubber, or silicone
Purpose of cuff
Protects airway and environment from contamination
Types of e-tubes
- Murphy- most common
- McGill
- Wire reinforced (do not use with MRI)
- Cole- avian
- Tracheostomy
What type of tube provides the least air resistance
Larger radium and shorter length (Poiseuille’s law)
Cat e-tube sizing
3.5-4.5mm generally
Dog e-tube sizing
8.0-12mm depending on size of dog
14-16mm for giant breed dogs
Sheep e-tube sizing
10-12mm
Horse e-tube sizing
26-30mm
Safe e-tube inflation
No audible release of gas around e-tube when pop-off is closed and reservoir bag is squeezed to 20cmH2O
Air should be escaping at 30cmH2O- prevents over inflation
Potential complications of intubation
- Laryneal damage- small animal espeically
- Tracheal damage
- over inflated cuff
- moving/twisting of inflated cuff
- Tube obstruction
- Endobronchial intubation (hypoxemia, tachypnea, cynosis)
- ETT inhalation/ingestion
Purpose of scavenging
Collection and transport of waste gasses from the anesthetic machine to a safe disposal area
Types of scavengers
Active and passive
Elements of a scavenger
- Collecting system (APL valve)
- Transfer system/interface
- Receiving system
- Disposal system
Olfacotry ppm of gasses
> = 125ppm
Exposure limits to anesthetic gasses
Scavenging principles
- Scavenge everything
2. No leak technique (
Passive scavenging system medium
Charcoal
F-air canisters; does not scavenge nitrous oxide
Passive scavenging piping
Atmosphere (window etc)
Active scavenging system
Piped vacuum (WHITE drop and tubing)
Charcoal scavenging advantages
- Absorbs hydrocarbons
- Does not release to ozone
- Portable
Charcoal Scavenging disadvantages
- Does not absorb N2O
- Limited flow
- Added resistance
- Weigh before use and record weight
- Discard with 50grams+ or after 8-12 hours continuous use
Active scavenging system flow rate capacity
30L/min
