Anesthesia Machine Flashcards
What signifies a failed low-pressure leak test?
A bulb is attached to the common gas outlet and squeezed to create negative pressure. If bulb reinflates in less than 10 seconds
How much negative pressure should be created for the negative pressure test?
-65cm H2O
Should the vaporizer be on or off during the low-pressure leak test?
Both. Off first to test flowmeters and then on one by one.
What does SPDD stand for?
Supply, Processing, Delivery Disposal
3 components of supply
electricity, pipeline, cylinders
Site of Supply component of SPDD
back of the machine
Site of the processing component of the SPDD
within the machine, proximal to the common gas outlet
Site of the delivery component of the SPDD
breathing circuit - both to and away from patient
Site of disposal component of the SPDD
scavenger
What organization is responsible for the compressed gas cylinders?
Department of Transportation
What organization is responsible for the scavenger system?
OSHA
occupational safety and health administration
Is the pipeline supply oxygen stored as a liquid or gas?
Liquid
What is the boiling point of oxygen? How is it stored as a liquid?
BP = -184 Celcius
Held under pressure to be stored as a liquid
How does it turn from a liquid to a gas? What pressure is oxygen supplied from the pipeline?
As it leaves the highly pressurized tank it almost instantaneously turns from liquid to gas and travels via pipelines at 50psi
Normal working pressure of gas machine?
50 psi
What is the DISS? How does it work?
Diameter Index Safety System
The pipeline inlet for the fresh gases (oxygen, air, n20) has different sizes/threads that only correspond to the appropriate gas tubing. And a check valve ensures unidirectional flow.
The pipeline pressure gauges should read about what psi?
50!
What is cross-connection regarding pipelines?
A rare mistake - but when nitrous oxide is coming out of the oxygen pipeline source
What monitors for low oxygen pressure in the anesthesia machine?
oxygen pressure failure device
What pressure system does the oxygen pressure failure device (failsafe device) reside in?
intermediate pressure system
The oxygen pressure failure device (failsafe device) will not alarm in the setting of?
pipeline crossover
crack in glass flow meter
What are the two components of the oxygen pressure failure device (failsafe device) that prevent a hypoxic mixture?
- Threshold alarm: sounds when oxygen pipeline pressure falls below 30psi
- Pneumatic system: reduces or stops the flow of n20 when the pressure in the oxygen pipeline falls below 20psi
Who sets the standards for the required components of the anesthesia machine?
ASTM
American Society for Testing and Materials
If your oxygen pipeline pressure supply fails? What do you do?
Switch to oxygen cylinder!
Newer machines switch to air to drive the ventilator if there is a loss of oxygen pressure. However, if you’re on an older machine that is using bellows, what will you want to do if this loss of oxygen pressure occurs?
Hand ventilate because you will lose more oxygen from your cylinder than the flow meter says because it is still being used to drive the machine. You will chew up your oxygen much faster than you anticipate.
Where can a cross-connect happen?
Anywhere! Always trust an oxygen analyzer until you can prove it wrong! (you calibrate it everyday with machine check)
What is the pressure distal to the cylinders?
Why is this important?!
45psi
Because pipeline is supplied at 50 psi - IF you were to leave the cylinder valve open - the machine would still use the pipeline pressure however if you loose pipeline pressure your machine will now use the cylinder and you wont know until your tank is empty!
Will your machine alarm if it switches to cylinder oxygen instead of the pipeline if you accidentally leave the cylinder valve open?
No!
DISS and PISS - which goes with which gas delivery system
DISS - pipeline
PISS - cylinder
Describe the PISS system
Pin Index Safety System
Pins on the back of the cylinder valve are placed in a unique arrangement to so that they can only be placed in the appropriate spot
3 functions of the hanger yoke
- orient the cylinders in the right direction
- provides a gas-tight seal
- ensures uni-directional flow
oxygen, air, and n20 PISS numbers
2,5 - oxygen
1,5 - air
3,5 - n20
What is the most fragile part of the cylinder?
cylinder valve
In the case of a fire near a cylinder - what are 3 safety relief devices
- Fusible Plug
- Pressure Valve
- Frangible Disk
What does the pressure safety relief valve do in the case of a fire near a cylinder? How does it work?
releases contents at a stable rate to avoid explosion
Frangible disk bursts, the valve opens, and the plug melts
The fusible plug is made from?
Woods Metal - aka it melts.
Max Service pressure for oxygen cylinder
1900 psi (2,000 acceptable for calculations)
Max Capacity for oxygen cylinder
660L
Max Service Pressure for Nitrous Oxide
745psi
Max Capacity for nitrous oxide
1590L
Max service pressure for air
1900psi
Max capacity for air
625L
A full oxygen tank contains how many Liters of oxygen
660L
How do you calculate how much time you have left on an oxygen cylinder at a given flow rate?
Tank Capacity / Full Tank (service) pressure
=
contents remaining (L) / current gauge pressure
This gives you Liters remaining. Then take the Liters remaining divided by the flow rate (L/min) to give you how many minutes you have left before the tank expires
Is nitrous oxide stored as a liquid or gas?
Liquid and turns to gas when close to empty (1/4 left)
The pressure of the nitrous gas cylinder will remain at 745psi until all liquid is gone, which equates to how much is gone. When should you change the cylinder?
3/4 tank empty when the cylinder has no liquid left. This is when you should change the tank!
At what rate of N20 would create frost on its wall or freeze the valve?
4L/min
A half-full oxygen tank will have about how much gas pressure and volume left?
about 1000 psi and 330L
What is the oxygen “color” in the US and internationally?
Green in US
White for international
What is the air “color” in the US and internationally?
Yellow in US
Black and White for international
Anesthesia machines will have at least how many minutes of battery if loss of power occurs
30 minutes
The traditional flowmeter (Thorpe Tubes) are the beginning of what system? It controls and measures the fresh gas flow that travels towards the?
Low-pressure system
Vaporizers and common gas outlet
Why must oxygen be the furthest flow meter to the right and common gas outlet?
Safest - for the patient and reduces risk of hypoxic mixture
T/F : A piston-driven ventilation gas machine utilizes oxygen as the gas driver
False. If you have a piston (aka electrical) system compressing the bellows, you do not need oxygen pressure / drive to compress the bellows and deliver the gas.
Describe the Link-25 Proportioning System to prevent a hypoxic mixture
A mechanical system linking N2O and O2 with a chain around the flow meter knobs. It prevents a serious hypoxic mixture by limiting the ratio of N20 and O2 to a 3:1 ratio.
The reading of any glass flow meter should be read at what point of the float device?
at the widest point of any float within the tube.
Ball (middle)
Oxygen Flush can supply how much oxygen?
35-75 L/min flow
To avoid barotrauma - when should you activate the oxygen flush?
If a ventilator is in use, do not use it during the inspiratory phase. Flush should be utilized in short bursts during the expiratory phase.
Why do we prefer to use oxygen to compress the bellows?
If the bellows allows gas to enter/mix with its inner contents, you’d prefer that to be oxygen
Humans consume how much oxygen per minute?
2-3ml/kg
Thorpe Tubes / Flow Meter Tubes are in which pressure system of the anesthesia gas machine?
Low Pressure System
Cylinder Pressure Regulators are in which pressure system of the anesthesia gas machine?
High Pressure System
Hanger Yokes are in which pressure system of the anesthesia gas machine?
High-Pressure System
Pipeline inlets are in which pressure system of the anesthesia gas machine?
Intermediate Pressure System
Vaporizers are in which pressure system of the anesthesia gas machine?
Low-Pressure System