Anaesthetic Machine Flashcards
What is the purpose of an anaesthetic machine?
To allow us to deliver gaseous inhalational anaesthesia at a steady flow. And allows adjustments to be made.
What are the colours of the gas cylinders for O2? N2o? Co2?
o2 - black body with white shoulders
n2o - blue
co2 - grey
What system is in place to ensure the correct cylinder is connected to the correct port?
The Pin Index System
What are o2 generators?
Use electricity to generate o2 from room air via a pressure sieve
What is the pressure gauge for and when is it unreliable?
Used to read the pressure of gas in the cylinder and indicates the remaining content
Unreliable for N2O as this is stored as part liquid part gas so the cylinder should be weighed
What is the function of the pressure reducing valve?
Safety mechanism between the cylinder and the gas outlet. Reduces the pressure of the gas coming out of the cylinder making it easier to control and allowing it to be delivered to the patient at safe pressures (avoids damage to the respiratory tract of the patient)
What is the function of a flowmeter?
Shows us the level of gas flow delivered to the patient. each one is gas specific.
Where should a bobbin be read from?
Where should a ball be read from?
Top
Middle
What is a vaporiser?
Contains the liquid volatile agent to be mixed with the carrier gas
What are the 2 types of vaporiser?
- In-circuit (uncommon)
2. Out-of-circuit (common)
What is an in-circuit vaporiser?
The vaporiser is included in the inspiratory limb of the circuit. The animal’s own respiratory efforts control the amount of volatile agent it receives.
What are out-of-circuit vaporisers?
Name the 2 types
Fresh gas flow from the machine vaporises the inhalational agent.
- Older style - Glass Boyles Bottle
- Modern - ‘Tec’ vaporiser
What are the disadvantages of using a glass boyles bottle vaporiser?
Many variables affect the output!
e. g. ambient temperature, liquid level, liquid temperature
- Not as accurate!
Describe a Tec vaporiser
- Allow controlled amounts of volatile agent to be delivered to the patient
- Adapted to compensate for various factors e.g. temp
- Various types of vaporiser for specific agents e.g. desflurane requires a special heat vaporiser
What is the purpose of the emergency o2 flush?
Delivers 100% o2 to the patient, by-passing the vaporiser and flowmeter. Used to dilute or remove agents from the circuit in an anaesthetic emergency. Should open valve first!
What is the function of soda lime?
Filters CO2 from the system. Changes colour as CO2 is absorbed
How can the risks associated with secondary breathing of anaesthetic gases by RVNs be minimised?
- adequate ventilated room
- Effective scavenging system in place
- Correct size ET tube
- Switch of gases before disconnecting patient
- All connection are air-tight
- Use key fillers to top up vaporisers
- Keep O2 on after volatile agent has been turned off
- Service equipment regularly
What is passive scavenging?
Large bore tube connected from APL valve to outside building or activated charcoal.
Tubing no longer than 2.6m to reduce resistance.
Relies on patient’s respiratory efforts and affected by resistance in tubing
What is active-passive scavenging?
Same as passive, but the tubing is connected to a forced ventilation system.
What is another name for an activated charcoal scavenge?
Aldasorber
What are the down sides of an aldasorber?
No cut-off when full so have to constantly weigh
Does not remove N20
Increases the resistance of the circuit
What APL valve stand for?
Adjustable Pressure Limiting valve
What is an active scavenging system?
- Completely efficient if correct design
- Composed of a pump connected to an expiratory valve containing suction that draws waste gases without affecting airflow to patient
