Anesthesia Machine Overview Flashcards
What do the components of the anesthesia workstation function to do?
deliver known concentrations of inhaled anesthetics to the patient
What does the anesthesia work station consist of?
anesthesia machine, vaporizers, ventilator, breathing system, scavenging system, respiratory and physiological monitors
What are the benefits and disadvantages of having everything in one workstation?
benefits: reduces chances of disconnections
disadvantages: variety of machines; learning curve for each one
What is something you have to do with a computerized AW?
power it down q24h
What is the common gas outlet?
where the AW provides delivery of medical gases and vapors of volatile anesthetics
What is the common place for disconnect at the AW? Where do gases mix prior to going to the patient?
common gas outlet
After the common gas outlet, where do the gases go?
they enter the anesthetic breathing system
How are the gases delivered to the patient?
via spontaneous or mechanical ventilation
How are exhaled gases removed?
scavenger; from the breathing system
What groups set the standards for AWs? What standards do they specifically set?
American Society for Testing and Materials (ASTM)= year 2000 and newer
American National Standards Institute (ANSI)= earlier than 2000
What are 5 pathways for O2 in the anesthesia machine?
- flow to fresh gas flowmeters
- powers the O2 flush valve
- activates the failsafe mechanisms
- activates the O2 low pressure alarm
- compresses the bellows of the vent
The pneumatic system is a _________pressure system. It has 3 levels, what are they?
air
high
intermediate
low
What does the high pressure system do?
reduces pressure from cylinder pressure to pressure suitable for use in the machine
What is the DISS? What does it provide?
Diameter Index Safety System; provides noninterchangable connections for the medical gas lines
What does the DISS consist of? Why is this important?
body, nipple and nut connection; only properly mated parts will fit together and allow the threads to engage
Is a DISS required or optional part of the anesthesia workstation?
required
What is involved in the intermediate pressure system?
pipeline sources of O2, N2O, air pressure regulators (2nd stage) Oxygen pressure failure device flow meter control valves flush valve
What is part of the low pressure system?
flow meter tubes hypoxia prevention safety device unidirectional valves (outlet check valve) pressure relief devices common gas outlet vaporizers/manifold
What is the pressure level of the low pressure system?
slightly higher than atmospheric
What is the O2 pressure sensor shut off valve?
safety valve downstream from the N2O supply source
What is the purpose of having the O2 pressure sensor shut off valve?
shuts off N2O or proportionally decreases the supply of N2O allowed into the machine if O2 supply pressure decreases to a predetermined threshold value (ie 25psi)
What are 2 different types of O2 pressure sensor shut off valves?
threshold: either on or off
proportioning type: OFPD responds proportionally to changes in O2 supply pressure
What types of cylinders are typically used for the AW?
E
What system allows only the correct tank to be attached to the correct hose on the AW? How does it work?
PISS: Pin Index Safety System
holes on the tank only allow specifically placed pins to fit in; #ed from left to right 1 to 6
What are the PISS settings for O2, N2O and air?
O2: 2 & 5
N2O: 3 & 5
air: 1 & 5
When is an E cylinder of oxygen considered full?
at 2000psi or approximately 625-650 liters of O2
What happens to the pressure of the O2 tank as O2 is used up?
pressure falls in proportion to amount of O2 left in tank
If a tank starts out at 2000psi and 625L of O2, then drops to 1000psi, how much O2 is left?
312.5L
If your O2 tank is half full and you are running O2 at 2L/min, how many hours do you have left before the O2 runs out?
2.6 hours (156minutes)
What does the number on the O2 pressure gauge on the cylinder reflect?
the volume of O2 stored as a gas
What is the volume of O2 in a cylinder if the psi is 2200, 1100, 550, 225, and O?
2200psi=625L 1100psi=312.5L 550psi=156.25 225psi=78L 0psi=0L
What is the psi of a full N2O tank?
745psi
What does a pressure regulator do?
reduces the pressure to a constant 45psi
What is a type of pressure regulator not in all machines?
second stage
What does a second stage regulator do? Where is it found?
reduces the pressure even more (14psi for O2, 26psi for N2O)
found downstream from pressure regulator
What is the purpose of a flow meter?
to measure gas flow to the common gas outlet
What are 2 types of flow meters?
Thorpe tubes; electronic flow sensors
What are some safety features of flow meters?
color coded; O2 flow knob is distinct; location of O2 flow knob
What are the color codes of the gases?
O2=green N2O=blue air=yellow
How is the O2 flow knob distinct?
distinctively fluted; projects beyond control knobs of the other gases; larger in diameter
Why is the O2 flow meter positioned downstream?
downstream from N2O prevents hypoxic mxture if leak is present: NOT FAILSAFE
What can happen if there is a leak in the O2 flow meter?
hypoxic mixture
What is the flow rate of the O2 flush?
35-75L/min
Where does the O2 flush go to?
directly to machine outlet–>patient circuit
What is a potential adverse effect of using the O2 flush?
potential for barotrauma
What is the only reasonable use for using the O2 flush?
aid in machine check; fill bellows on expiratory phase of respiration
What is a safer way to fill the bellows?
turn up O2 flow meter
What does using the O2 flush not replace?
a good mask fit
When is the anesthesia machine checked?
- complete and thorough daily check
2. circuit check before each new case
What is the best monitor at your disposal?
VIGILANCE
What are monitors effective in doing?
detecting problems with or adequacy of ventilation and oxygenation
What are common monitors you will see?
EKG, SBP, temp, O2 sats, CO2, anesthetic gases and vapors, alarm systems
What monitor is the best for detecting a disconnect? What else may show this?
ETCO2
low pressure alarms
What is the most important monitor on the machine? What does it do?
Oxygen analyzer
detects if machine is getting correct FIO2
What do you want to calibrate the O2 analyzer to?
21% O2; room air
What monitor provides ongoing monitoring of exchange?
SpO2
What are you checking in a machine check?
gas line connections; vent check; flow meter controls; vaporizer levels; O2 analyzer; low pressure circuit leak check; circle system test; work station self tests
What is the only monitor that detects problems downstream from the flow control valves?
oxygen analyzer
What is the process of checking the O2 analyzer?
expose O2 sensor to room air for given amount of time
What is the purpose of checking the low pressure circuit test?
checks the integrity of the machine from flow control valves to the common gas outlet
What parts of the machine are most vulnerable to breakage?
components in the low pressure circuit
Is there 1 specific way to check the low pressure circuit?
no; differs w/ machine depending on whether or not the machine has a check valve
For a 1993 FDA negative pressure leak test, what switches must be turned off or on?
machine master switch, flow control valves, and vaporizers: all must be in OFF position
What is the suction bulb attached to for a leak test?
common gas outlet
Why is the suction bulb squeezed several times in a leak test? How do you know if the machine is leak free?
squeeze until it is fully collapsed: this creates a vacuum in the low pressure circuit
bulb remains collapsed for at least 10 seconds
What is the purpose of a circle system check?
evaluate the integrity of the circle breathing system
Where does the circle breathing system extend from?
the common gas outlet to the Y piece
How do you perform a leak test of the circle system?
occlude the Y piece, close off APL valve, pressurized the circuit to 30 cm H2O using the O2 flush valve
What are you looking for on the leak test of the circle system?
sustained positive pressure reading on the airway pressure gauge
What does a leak test of the circle system not test?
the integrity of unidirectional valves
What does test the unidirectional valves?
flow test
How do you perform a flow test of the circle system?
attach breathing bag to Y piece, turn on ventilator and assess integrity of unidirectional valves
What will dilute the anesthetic if you use it on the patient?
O2 flush valve
What prevents backflow of gas?
outflow check valve
What is the main component of the high pressure system?
tanks
What is the psi that the gas in the tanks is reduced to?
45psi
What is the psi that the gas from the pipeline is reduced to?
50psi
What is the main component of the intermediate pressure system?
pipeline
What is the symbol for the Oxygen flush valve?
O2+
The flow meters are part of the _________pressure system but the knobs are part of the __________ pressure system.
low
intermediate
Describe the hypoxic prevention device.
oxygen is always downstream from N2O (O2 is closest to vaporizer)
this way if there is a crack in the system, O2 will still be pumped to patient
If you turn on N2O before O2, O2 will turn up to 30% before N2O turns on
Also, if you turn O2 down, N2O will decrease as well
If the O2 pressure shut off alarm goes off, what will the workstation do?
What will it not do?
it will turn off N2O and air and only give patient O2
It won’t turn off the anesthetic
What does the O2 pressure shut off valve not respond to?
FiO2
If the O2 fail safe alarm goes off, what should you do?
disconnect the pipeline and use the cylinder
If your patient is on O2 and you want to decrease your FiO2 from 100% at 10L/min to 50% @ 10L/min, how do you adjust your gases if you are using O2 and N2O?
give 5L/min of both O2 and N2O
