Processing Flashcards
What is considered the processing aspects of the anesthesia machine?
The areas distal to where the gases enter the gas machine and extends to the area proximal to the common gas outlet
What is the only gas that does not pass via fail-safe mechanism
Oxygen, always added last
Once the gases enter the common manifold, where do they go next within the machine?
Vaporizers to pick up the anesthetic agent
After picking up anesthetic agents from the vaporizer, the new mixture enters which part of the gas machine?
Common gas outlet (Dalton’s Law)
If you forget to close the oxygen tank after checking it why wouldn’t there be flow from the cylinder?
One way check valves would be closed by higher pressures in pipeline supply
What are the five tasks of oxygen?
- Powers the fail safe valve (keeps the valve open) O2 is the driving gas that will turn off all other gases
- Drives the anesthesia ventilator
- Travels from the needle valve to the flow meters themselves
- Provides pressure to prevent the low pressure alarm
- Oxygen flush valve
This system was designed to prevent unintentional delivery of a hypoxic mixture to the flow control valves
Fail-safe Design system
How would a hypoxic mixture be possible under the Fail safe design system?
If the gas holding open the pressure valve is not oxygen a hypoxic mixture is possible
What does the Fail-safe design system do if the O2 supply pressure falls below threshold setting?
O2 pressurizes and holds open a pressure sensor shut off valve that reduces or interrupts supply of N2O and other gases to their flow meters
How is N2O typically released into the circuit?
O2 pressure forces a piston up on the spring that will open a valve (fail-safe) and allow N2O to flow
What type of valve is the fail-safe valve?
Ball and spring type valve, all or nothing arrangement that is open at O2 pressure > 20 psi and closed at lower pressures
When will the Drager and Ohmeda gas machines low pressure alarm go off?
Ohmeda less than 28psi
Drager less than 37psi
What should be done if the low pressure alarm goes off when using pipeline supply?
Immediately switch to emergency cylinder supply, unplug the pipeline supply, switch to manual ventilation mode and low flows
What are the five components of a flowmeter?
Knob Needle valve Valve stops Flow tube Indicator float
What is another term used for flowmeters?
Rotameters
What is the basal metabolic rate/consumption of a patient?
200-300mL/min this is the same default of minimum O2 flows as the anesthetic gas machine
What is the purpose of the needle valve?
It controls gas flow, by turning the needle valve counter clockwise the orifice becomes larger, increasing flow of O2
Device that prevents damage to the needle valve from excess force?
Valve stops
What safety features are implemented on the flowmeter control knobs?
Color and touch (O2 fluted knob)
What is the accuracy of a Thorpe tube at room temperature?
Accuracy 2-3% at room temperature and 760mHg
Why aren’t Thorpe tubes interchangeable?
The diameter is gas specific
What represents the variable orifice?
The area between outside of the bobbin and inside of the glass tube
What causes the ball/bobbin to float in a flowmeter?
A certain pressure difference across the bobbin/ball
What indicates the flow of gas in a flowmeter?
The ball or bobbin rotating
Where do you read the ball and the bobbin?
The ball is read in the middle and the bobbin is read at the top
Why are two flowmeters presents for each gas?
Allows accurate measurement at high and low flows
Low flowmeter up to 1Lpm
High flowmeters up to 10-12Lpm
Why is oxygen positioned closest to the common gas outlet?
A leak in any other flowmeter tube least likely to affect oxygen supply to patient, ensures accidental decrease in delivered O2 (hypoxic mixture)
Electronic flowmeter are considered how much more accurate than flow-tubes?
5 times more accurate
What is considered a hypoxic mixture?
less than 21% O2 in any total concentration
