Anaesthetic machine Flashcards
What are the 3 roles of the anaesthetic machines?
- artificial atmosphere which is delivered to the patient
- To maintain general anaesthesia by mixing the general anaesthesia with fresh gas flow
- emergency life support by IPPV
What kind of machines are there?
- portable machines
- wall-monitored units
- complex units
What is the most NB function of the anaesthetic machine?
- supply of gas
- measurement of gases
- anaesthetic vaporisers
- breathing circuits
- use as resuscitation apparatus
Which gases are liquid when compressed in cylinders?
- Nitrous oxide
- CO2
You need to weigh them to determine whether they are empty or full
Which gases are still gases in the cylinders?
- Air
- nitrogen
- oxygen
The pressure inside gives an indication of what’s going on in the cylinder
What happens when the oxygen runs out?
A ritchie whistle will blow
What is the minimum amount of oxygen that can be delivered during anaesthesia?
30%
What is the reason for giving 30% of oxygen?
-There is an increase of ventilation and perfusion mismatch during general anaesthesia
What is fresh gas flow?
It is when there is a continuous supply of a minute volume of fresh gas to the patient
What does minute volume consist of?
Tidal volume and x frequency
If the patient is under mechanical ventilation then 8mg.kg delivered at 9 breaths per minute is fine
What are flow meters?
Flow meters are tubes that have measures of selected gases that have a plastic ball or arrow above
Where is the anaesthetic gas contained in? And what is NB about the vaporiser?
A vaporiser
There are multiple vaporisers on the machine and we cannot open many of them at a time because it leads to contamination of the downstream vaporiser
What is the splitting ratio?
The anaethetist is able to adjust the dial on the vaporiser and determine how much of the fresh gas flow contains the anaesthetic drug and how much does not
What is the emergency oxygen given to the patient?
It is oxygen that does not have the anaesthetic drug and is up to 20 litres.min
If it is left open for long enough it will lead to the patient waking up
What are the 2 breathing systems?
- Rebreather
2. Non-rebreather
How does the rebreather system work?
- The gas that is not used up by the patient is used up again and oxygen is added to the mix
There is a chance of CO2 accumulation in which a CO2 absorber is utilised
Where does the expired gas from a patient go?
It goes outside of the operating room
At what measurement should a functional suction apparatus read after 1 minute?
400-600 cm H20 pressure
What is important about having an ambubag closeby?
It is essential to have positive pressure ventilation to compensate for if the oxygen cannot be administered by the machines for some reason
What is the main breathing system used?
-What does it have attached?
Ayres T piece or the Mapleson E
- P= patient
- F= fresh gas flow
- R= reservoir
What is the modification with the reservoir bag and the Ayres T piece?
The Jackson-Rees modification
What is another name for the spring loaded valve mechanism?
Mapleson D system
How do we ensure that the fresh gas flow is at a high enough rate to get tp the patient?
Increase the rat to approximately 2.5-3 times the patients predicted resting minute volume
What is another name for the Magill’s breathing system?
Mapleson A- this has a spring valve a or close to the patient’s mouth
Which system is best for controlled ventilation and not spontaneous ventilation?
T piece system
Which system is best for spontaneous ventilation and not controlled ventilation?
Magills breathing system
What is the Bain’s system?
Mapleson D
-It has fresh gas flow running through the large resevoir tube and is a coaxial system
What is the fresh gas flow that is needed for spontaneous ventilation that is required for the T-piece?
-2,5 to 3 times of the patients minute volume
What is the fresh gas flow needed for controlled ventilation?
1 times the minute volume of the patient
Which patients do we usually use the Ayres T piece in?
-Children less than 20 kilograms
What are the disadvantages of using the T-piece?
- It wastes fresh gas flow if spontaneous breathing is applied
- the bag/ventilator may get twisted and stop breathing
What are the advantages of the Ayres T piece?
- It is economical for controlled ventilation
- minimal dead space
- low work of breathing
What are the 3 possible causes of ETC02 of 0mmHg?
- tube in the oesophagus
- cardiac arrest with prolonged downtime
- spontaneous apnea
What is the DOPE pneumonic in regards to ETC02 reading 0mmHg?
D-dislodgement
O-obstruction
P-pneumothorax
E-equipment
