the Anesthetic Machine Flashcards
3 types of AM:
Portable
Wall-mounted
Complex unit
What is the content of mixed gas delivered to the pt?
O2 + N2O / air
Plus your anesthetic gas
What are the 5 essential components of the AM?
Oxygen supply Measuring gasses Anesthetic vaporisor Breathing circuit Rescuss apparatus
How are the following gasses stored?
- N2O
- O2
- N2
- Air
- CO2
- Liquid compressed
- Pressure -stays gas
- Pressure - stays gas
- Pressure - stays gas
- liquid when compressed
How will you measure amount of gas in these cylinders and why?
N2O
O2
N2O froms a liquid when put under certain amount of P. Difficult to measure amount left because pressure remains constant untill 80% of fluids vaporised - THUS weigh bottle
O2 stays in gaseous form under pressure, this amount left can be measured by means of measuring the Pressure in cylinder.
T/F:
CO2 must stay connected to the AM as it causes no harm due to the fact that the valve stays closed during the procedure.
False
CO2 must be disconnected to prevent any accidental administration to a pt, which would be fatal.
Define the “Pen index”?
System used to prevent pipeline being connected to the wrong outlet in wall. Configured to only allow the correct gas to fit to correct plug.
*it is the hospitals responsibility to ensure that the correct gas will indeed be administered through the outlet - But keep in mind
If all other causes are excluded for pts poor ventilation rather use ambubag and ventilate manually
What are the colors of these gas cylinders? Why the colorcoding?
- Oxygen
- Nitrogen
- Nitrous oxide
- Air
- Entenox (50:50 ratio)
- Carbon dioxide
- Vacuum system
- White
- Black
- Blue
- White and black blocks
- White and blue blocks
- Grey
- Yellow
What happens when oxygen supply cut off or diminished?
Why?
Ritchi whistle goes off
Other gasflow will be cut off
If oxygen stops the pt will develop hypoxia, by cutting off all the other gasses identification of Px can happen more readily.
What will prevent high pressure from storage being directly transfered to machine and pt?
Pressure reduced stepwise by means of:
Pressure reducing valve BEFORE delivered to AM and pt.
What is the Pa of oxygen in air?
How much in anesthetic circuit?
Why must it be adapted?
21%
30%
2 reasons:
Raised V/Q mismatch
Exhaled air usually saturated with water vapour.
THUS
Account for 10% of dilution og AG delivered to AM due to the gas being of high purity and dry.
Minute volume = ?
Frequency x tidal volume
Define fresh gas flow?
Determined by?
Continous supply of fresh gas (minute volume)
Type of circuit
Whether pt is breathing spontaneously/ ventilated
What is the tidal volume for pt that is ventilated?
At what freqeuncy?
8mg/kg delivered at
9 breaths/ min
Henry’s Law:
Amount of gas in solution will be equal to PaP of that gas in solution.
Thus [gas] in blood directly related to PaP of gas administered to pt.
What does a flow meter do in the AM?
Measure gas flow for each selected gas that will be administered to the atmosphere of pt.
Re different flow meters:
Ball measurement?
Arrow measurement?
Unit of measure?
Ball: middle of ball
Arrow: top end of arrow must be used
Litres/min
Problem solving practice:
If the fresh gas mixture contains 1.5l/min of oxygen and 1.5l/min of N2O.
What is the mixture called?
50% oxygen atmosphere
Explain the fundamental principle of the anesthetic vaporiser (AV)?
Any Px that may occur?
The Splitting ratio.
First understand that the vaporisor allows the anesthetic drug to be added to the fresh gas mixture.
Fresh gas flows through the vaporisor
Part is diverted through the vaporiser
Part bypasses it
Both of these portions meets up again is administered to pt.
Px: remaining fluid that is not vaporised will cool = decrease in vapour pressure.
Solution: having a stable vapour pressure for gas flow - 1-10 L/min
At what side of the AM is the emergency oxygen inlet situated?
At what flow rate is this set?
Does it pass through the vaporisor?
What effect will this have on the drug?
Pts side
20 L/min
No
Dilute the drug and the pt will awaken
What is the final gas mixture?
Fresh gas mixture
Anesthetic drug
Name 2 breathing sytems that are used to administer final gas mixture?
Rebreathing
Breathing
Explain the rebreathing system?
What flow will be used?
What gas might accumulate?
How will you correct for this?
Gas not used, returns to inspired section, while small amounts of oxygen added to make up for what pt has extracted from mixture
(Anesthetic drug reused)
Low flow
Carbon dioxide accumulation
Carbon dioxide absorber - soda lime
Process of AM:
Gas flow and oxygen (rotameter) Fresh gas flow Anesthetic vaporisor (splitting ratio) Emergency oxygen if needed Breathing circuit( re- or non rebreathing) With /without CO2 absorber Excess exhaled gas vented to atmosphere
How will exhaled gasses be vented to atmosphere?
Aka: vacuum system
Low negative pressure system - collects expired gasses and delivers to outside operating room.
How is suction tested for the vacuum system?
Can you apply direct wall suction to the outlet rsponsible for extracted exhaled gasses?
Occlude the suction pipeline
Negative pressure of 400- 600 cm H2O
Should be achieved within 1 minute
never, total gas volume to pt will be sucked out
Ix for positive pressure ventilation?
How will youndo this?
Pt paralysed
Stopped breathing for any reason
Ventilator failure
Ambu bag ( functional reservoir bag) Correct connecting pieces Emergency: bag pt with room air and maintain anesthesi with IV drugs
Minumum requirement for AM:
Monitor for A/w pressure and inspiratory [oxygen] Warning system for low gas pressures Suction Ventilator Audible warning against O2 failing
What is the content of soda lime?
4% calciumhydroxide
1% potassium hydroxide (speeds up rxn)
Granules must be large enough for chemical rxn
Water is needed
Contains ethyl violet (ph indicator dye) :
- gives color change when absorbent exhausted
Ph 10.5
Chemical rxn of carbon dioxide and absorbant:
Water + CO2. = H2CO3
CO2 + 2NaOH. = Na2CO3 + 2H2O + heat
Na2CO3 + Ca(OH)2. = 2NaOH + CaCO3
Three purpose of Anesthetic machine:
A- arteficial atmosphere
B- breathing apparatus
D- delivery of anesthetic gasses
