Breathing Systems Flashcards
Describe a Magill Circuit
Non rebreathing
- Valve near patient
- Bag at machiene end
- Alveolar gas vented, dead space gas rebreathed
- Requires expiratory pause to function correctly (time for fresh gas to fill tube)
Give the flow rate for a Magill or Lack circuits
0.7-1 x MV
What circuits can be used for Medium sized dogs breathing spontaneously?
Magill, Lack and Bain
Describe a lack circuit
Modified mapelson A
- Non Rebreathing
- Inefficient for IPPV
- Parrallel (bag and valve at same end but different tubes
- For dogs over 10kg
Describe a mini lack circuit
- Non rebreathing
- Smooth inner bore tubing and lightweight valve = minimal resistance
- 1/3 flow rates of a T piece
for patients 2-10kg
What circuits can be used for patients from 2-10kg
Mini lack and T piece
Describe a bain circuit
- Non rebreathing
- Inner tube provides fresh gas directly to the patient
- High flow rates
- Excellent for IPPV (squeezing bag returns gas from expiratory limb into the patient)
What is the circuit factor for the Bain
2.5
Describe the T piece breathing circuit
- Non rebreathing
- No valve
- Low resistance
- Good for IPPV
What is the normal minute volume for an animal
250ml/0.25L per kg
How do you work out flow rates for an animal?
Circuit factor x Weight x 0.25 = L O2 required
Describe how you would work out minute volume
= Tidal volume vs resp rate (normally 0.25L per Kg in an animal)
Describe a to and fro circuit
- Rebreathing
- outdated
- dust inhailation etc
Describe a circle breathing circuit
- Efficient
- Warm and humidify air
- less pollutant
- Easy IPPV
- Use Y tubing
- One way valve system
What chemicals are usually used as absorbants in rebreathing systems
- Calcium Hydroxide(soda lime)
- Incorporates indicator to usage (check before use)
- Active soda lime generates heat (detectable by touching the cannister)
Describe rebreathing systems
- Unidirectional gass flow maintained by valves and force of patients breath
valves must be checked prior to use - Volume of bag must be greater than patients inspiratory capacity
What is the constant for the patients inspiratory capacity?
30ml/kg bodyweight
Describe the considerations when supplying gas in a semi closed circuit
FGF must exceed the patients O2 consumption
Start anaesthetic higher to prime the system
What are the correct flow rates to use for dog anaesthesia
Initially 2-3L/min
Down to 500ml/min - maintenance
What are the correct flow rates for large animals
Start at 8-10L and then reduce
Give three advantages of lower flow rates
- Less waste
- Cheaper
- Less pollutant
What must you do if you wish to change the plan of anaesthesia
Increase flow rate and increase or degrease anaesthetic
Give the iso percentages for rebreathing and non rebreathing circuits
Non = 2% Rebr = 4%
