Apex- Anesthesia Machine Flashcards
Where does the high pressure system begin and end?
intermitediate pressure system?
low pressure system?
Cylinders → Cylinder Regulators
Pipeline → Flowmeter VALVES
Flowmeter TUBES → common gas outlet
What tests the integrity of the low-pressure circuit from the flowmeter valves to the common gas outlet?
how is it done?
what would signify an issue?
low-pressure leak nest
attach a bulb to the CGO and create neg pressure
- must be performed with teh vaporizers off, and then again with each vaporizer turned on one at a time
- if the bulb inflates, theres a leak in the system
Components of the high-pressure system (4)
Components of the intermediate-pressure system (7)
Components of the low-pressure system (4)
Pipeline vs tank psi
Pipeline = 50
Tank = 45
T/F: when doing a low-pressure leak test, the FGF must be off
True
if you have a vent with a minimum FGF- you have to turn off the machine to do the test
when doing a low-pressure test, should you be on the bag or vent?
bag
low pressure tests from flowmeter VALVES to CGO
How often should the low-pressure test be performed?
before the first case of each day
lol
PISS vs DISS
PISS- pin index - prevents wrong cylinder
DISS- diameter index - prevents wrong pipeline
PISS configurations for Air
O2
Nitrous
Air 1,5
o2 2,5
nitrous 3,5
The O2 cylinder pressure drops from ~2,000psi to what psi upon entry into the intermediate system
why?
~45 psi
to ensure gas is preferentially puplled from the pipeline if a cylinder is left open
(pipeline ~ 50psi)
Why should there only be one washer between the hanger yoke assembly and the stem of the tank?
bc more than one may allow for the PISS system to be bypassed
Service pressure and max volume of:
O2
Air
N20
O2= 1900psi/660L
Air = 1900psi/625L
N20= 745psi/ 1590L
service pressure of nitrous oxide
745psi
1590L
maximum volume of nitrous oxide in an e-cylinder
1590L
745psi
why does nitrous oxide exist as a liquid inside the cylinder?
bc it’s critical temp is above room tempearure (~36.5)
-critical temp is the highest temp a gas can exist as a liquid
How many L of nitrous oxide gas is remaining in the tank when there is no more liquid present
what about 400psi
250L
400psi = 136L
t/f: the cylinder valve is the most delicate component of the cylinder
True
the silver part on top - this is why a cylinder needs to be stored in an upright position
bc if it falls down and goes boom, and the top silver piece breaks off (the cylinder valve) - the o2 tank becomes a missle
why do we need to stand up the cylinder tank in a locked postion when not in use? what wil lhappen if it falls?
if it falls, the cylinder valve (the top silver piece) can break off (it’s delicate) and then the o2 tank can become a missle
What makes a o2 tank MRI safe and how can you tell that it is?
-made of aluminum
-mainly silver with the top portion being the color of the gas it contains (green = o2)
*but the best way to determine the contents is to READ the label- not examine the color
What kind of safety relief device is made by woods metal
what’s in woods metal
when would it provide safety and how?
fusible plug
BLT with Cheese- Bismuth, Lead, Tin, Cadmium
in the event of a fire, it would melt, to slowly release o2 contents - instead of exploding
What’s in woods metal
Bismuth
Lead
Tin
Cadmium
BLT with Cheese
Weight of a full nitrous oxide tank vs empty
full = 20.7#
empty= 14.1#
oh come on
World Health Organization colors for Air, O2, and Nitrous
Air = black and white
O2 = white
Nitrous = blue
Does Carbon dioxide exist as a liquid or gas inside the cylinder
max volume?
service pressure?
liquid
1590L (same as nitrous)
838psi
T/F: if youre changing the cylinder on the andesthesia machine, it’s ok to lay the cylinder on its side temporarily
True
If you remove a cylinder from the anesthesia machine but don’t have a replacement, what do you have to do?
Insert a yoke plug
If you open the cylinder and hear a hissing sound- what does that indicate and what do you need to do?
leak
-tighten the connection
T/F: if there is a leak, add an additional washer between the cylinder and hanger yoke assembly
FALSE- dont do this - allows bypassing PISS
Which gases are oxidizers
fire triangle components?
nitrous oxide and oxygen
oxidizer, fuel, igniter
Gas cylinder should never be exposed to temps above what degrees (F + C)
130 degrees F
57 degrees C
why shouldn’t you oil the cylinder valve
bc it increases risk of fire
What would happen if you didn’t insert a yoke plug in an empty cylinder spot?
If the check valve were to fail & there is no cylinder or yoke plug - gas that should be going to the patient will exit the anesthesia machine
Match: American Society for Testing and Materials (ASTM), FDA, OSHA, DOT:
-sets the standards for the required components of the anesthesia machine
-sets standards for compressed gas cylinders
-sets standards for acceptable occupational exposure to volatile anesthetics
-creates standard machine checkout procedures
-sets the standards for the required components of the anesthesia machine - ASTM
-sets standards for compressed gas cylinders- DOT
-sets standards for acceptable occupational exposure to volatile anesthetics- OSHA
-creates standard machine checkout procedures- FDA
A cylinder must be tested how often?
it’s tested to how many times it’s service pressure?
every 5 years -10 years with a specia permit indicated by a 5-pointed star on the label
1.66x it’s service pressure
7 pieces of information required on the cylinder label according to US DOT
- Government agency (DOT)
- type of metal
- max filling pressure
- serial number
- manufactorer
- owner
- date of last inspection
What monitors for low oxygen pressure in the anestheisa machine
another name for it
3 instances it would alarm
Oxygen-Pressure Failure Device
Fail-safe device
- depleted o2 tank
- drop in pipeline pressure
- disconnected o2 hose
T/F: the failsafe device will alarm in the setting of an o2 pipeline crossover
False- the failsafe device monitors pressure - not o2 concentration
2 components of the failsafe device (o2 pressure failure device)
does it reside in the high, intermediate, or low pressure system?
- **a threshold alarm **that sounds when o2 pipeline pressure falls below 28-30psi
- A Pneumatic device that *reduces or stops the flow of nitrous oxide *when the pressure in the o2 pipeline falls *below 20psi *
Does the fail-safe device monitor pressure or concentration
pressure
What would you do if you suspect a pipeline cross over? 2 steps
- open o2 cylinder on machine
- disconnect o2 pipeline from machine
Which machines failsafe device stops nitrous commpletely when o2 psi < 20 vs proportionatlly :
drager vs GE Datex-Ohmeda)
Drager - proportional decrease
GE Datex-Ohmeda - all or nothing
How would you know if the o2 pressure failure device is working?
okay so the o2 pressure failure device alarms when psi <30
apex says to turn on o2 and nitrous flow
verify o2 cylinder is closed
then d/c the o2 pipeline
once o2 source is disconnected, watch the flow meeters and the nitrous oxide flow should stop before the o2 flow stops
retinruducing the o2 pipeline should result in both gases restored to previous flow rates
The hypoxia prevention safety device will:
A. Shut off the flow of nitrous oxide if the o2 supply pressure is < 30psi
B. limit the nitorus flow to 3x the o2 flow
C. Alarm if the Fio2 is < 21%
D. prevent a hypoxic mixture if a third gas is used
B
When you’re administering nitrous oxide, the proporitioning device ensure that the FiO2 never drops below what % ?
25%
The proportioning device maintsins a max of what ratio of nitrous to o2?
3:1
T/F: the proportioning device will prevent hypoxia with the administration of a third gas
False
ie) helium
T/F: the o2 pressure failure device and the hypoxia prevention safety device are not the same thing
True
pressure failure device = fail-safe device
hypoxia prevention safety device = proporitoning device
What is the oxygen-ratio monitor controller
monitors the ratio of o2 to n20 (drager machine)
automatically adjusts n20 to go no grater than 3:1 (pneumatic device)
What is another name for the proportion device?
Hypoxia prevention safety device
The internal diameter of the flow tubes are (narrowest/widest) at the base and (narrows/widens) with ascent
narrowest at the base
widens as it goes up
To monimize the risk of hypoxic mixture in the setting of a cracked flowmeter, the O2 flowmetere should be positionined where?
where is this location on US machines?
closest to the common gas outlet
Far right
T/F: flowmeters are calabritated for each specific gas
True
What is the space between the ball float and the wall of the flowmeter called
the annular space
T/F: glass flowmeters resists the buildup of static electricity
True
Should o2 be positioned first or last in the sequence of flowmeters
last/downstream
ie) closest to the CGO/pt
incase there is a crack in any of the upstream flowmeters - this prevents a hypoxic mixture
but a crack in the o2 flow meter can still produce a hypoxic mixture
At high FGF, gas flow is (turbulant/laminar) and depdendent on gas (density/viscostiy) - what law
At low FGF, gas flow is (turbulant/laminar) and depdent on gas (density/viscosity) - what law
High FGF- turbulent- density- grahams
Low FGF - laminar, viscosity, pousilles
What is the o2% delivered with 1L air and 3L o2
80%
[Air flow rate x 21) + (O2 flow rate x 100)] / Total flow rate
1 x 21 = 21 + 300 = 321/4 = 80.25
O2 nasal cannula %s:
1L-
2L-
3L-
4L-
5L-
6L-
1L- 24%
2L- 28%
3L - 32%
4L- 36%
5L - 40%
6L - 44%
RA = 21% - then just go to 24% and add by 4
% of O2 delivered with a nasal cannula can range from what
24-44%
Steps in figuring out tidal volume with FGF is coupled to it
- convert FGF from L/min to ml/min
- multiply FGF by I:E ratio
- Calculate the tv per breath (FGF/RR)
- Add volume set on vent to FGF during inspiration
- I:E ratio of 1:2 means over 1 minute, 20 seconds is spent in inspiration and 40 in expiration
- said another way, 1/3 spent in inspiration and 2/3 spent in exhalation
- so for #2- if I:E ratio is 1:2, your multipling by 1/3 or 0.33333
A vent if programmed to deliver a tidal volume of 600mls. If the breathing circuit compliance is 5ml/cm H20 and the peak pressure is 25cm H20, what is the total tidal volume delivered to the patient?
A. 425mls
B. 450mls
C. 475mls
D. 500mls
C. 475 mls
5ml/cmh20 x 25cm H20 = 125ml
600 - 125ml = 475mls
*when the vent produces postive pressure inside the breathing circuit, some of this gas causes the circuit to expand. This quantiy of gas doesnt reach the patient and doesnt contribute to the tidal volume the pt recieves
Change in volume/ Change in pressure = what?
compliance
The isoflurane dial is set to 2%. What % of fresh gas exiting the vaporizing chamber is saturated with isoflurane? Enter your answer as a percentage
100%
Modern variable bypass vaporizers split fresh gas into 2 parts:
- some fresh gas enters the vaporizing chamger and becomes 100% saturated with the volatile agent
- The rest of the fresh gas bypasses the vaporizing chamber and does not pick up the anesthetic vapor
Before leaving the vaporizer, these two fractions mix, and this determines the final anesthetic concentration exitin the vaporizer
What does it mean when a vaporizer is “variable bypass?”
it means when fresh gas enters the vaporizer, someo f it encounters the liquid anesthetic and the rest bypasses it.
You determine the splitting ratio (how much fresh gas contacts the liquid) by setting the concentration on the dial.
What does it mean when a vaporizer is “flow-over”
so as fresh gas enters the vaporizing chamber with the liquid anesthetic, it flows over a series of baffles and wicks.
The baffles and wicks increase surface area and turbulence, ensuring the fresh gas incide the vaporizing chamber becomes 100% saturated with the anesthetic agent
variable bypass vaporiziers:
-flow-over wick
-temperature compensated
-out-of-circuit
-agent specific
T/F: the temperature compensating valve on a vaporizer adjusts the ratio of the vaporizing chamber flow to bypass flow and guarantees a constant vaporizer output over a wide range of temperatures
True
variable bypass vaporiziers:
-flow-over wick
-temperature compensated
-out-of-circuit
-agent specific
T/F: the variable bypass vaproizer is positioned OUTSIDE of the breathing circuit
true
variable bypass vaporiziers:
-flow-over wick
-temperature compensated
-out-of-circuit
-agent specific
T/F: variable bypass vaporizers are agent specific
True - each vaporizer is calibrated to one anesthetic agent. Fillling a vaporizer with the incorrect anesthetic can lead to catastrophic errors in output
variable bypass vaporiziers:
-flow-over wick
-temperature compensated
-out-of-circuit
-agent specific
T/F: variable bypass vaporizers automatically compensate for vaporizer output at changes in elevation
True
Vapor pressure is (directly/inversely) proportional to temperature
directly proportional
increased temp = increased vapor pressure
What describes the # of calories needed to convert 1g of liquid into vapor without causing a change in temp
Latent heat of vaporization
What is the most common cause of a vaporizer leak?
what could it result in?
a loose filler cap
awareness
What is the most common cause of a vaporizer leak?
what could it result in?
what part of the machine check would detect a vaporizer leak?
a loose filler cap
awareness
a low pressure system check (with the bulb)
How do you calculate how much liquid anesthetic your using per hour in mls?
volume % x FGF (L/min) x 3
What can happen if the vaporizer is tipped?
liquid anesthetic can spill from the vaporizing chamber to the bypass chamber
–> this can increase vaporizer ouptut and result in anesthetic OD
1mL of liquid produces howmany mLs of anesthetic vapor?
200mls
what 2 things should you do if a vaporizer tips
how do you know when it’s okay to use again?
- drain the vaporizer to remove the anesthetic liquid
- turn the dial to it’s highest % (8) and run high FGF through it for 20~30mins
when the end tital agent reads 0
What’s it called when the gas that has left the vaporizerl, re-enters it, thereby increasing the concentration of anesthetic leaving the vaporizer?
what 2 things can lead to this?
what eliminates this concern?
the pumping effect
PPV + use of the o2 flush valve
The presence of a check valve between the vaporizer and the CGO
Flows less than what or greater than what can lead to reduced vaporizer output?
flows less than 200ml/min
or > 15L/min
Does a variable bypass vaporizer need to be calibrated for elevation?
no
What best describes the TEC 6 vaporizer (select 2)
-It is pressurized to 2 atmospheres
- It uses a flow-over design
- it is heated to 42 degrees
- its ouptut is increased inside a hyperbaric chamber
-it’s pressurized to 2 atmospheres
-its output is increased inside a hyperbaric chamber
-it injects anesthetic vapor into the fresh gas (not flow-over design)
- it’s heated to 39 degrees (not 42)
- output varies inversely with elevation (high elevation, decreased pressure, decreased ouput; low evelvation, high pressure, high output)
*therefore, the vaporizer should be re-calibrated when itis going to be used in high-altitude locations
The Tec 6 is heated to what temp
39 degrees C
Des’s vapor pressure and boiling point
significance?
Vapor pressure = 669mmHg
Boilign point = 22.8 degrees C
vapor pressure very close to ATM (760)
boiling pont very close to room temp
*makes it des very volatile and very difficult to control at room temp; so small changes in room temp can signficantly alter vaporizer output
Why is Des heated?
what is it heated to
bc it’s boiling point is close to room temperature making it’s output difficult to control at room temp
-any increases or decreases in room temp would alter the output
39 degrees C
allows for a more controlled, consistent output
Which device will be the FIRST to detect an oxygen pipeline crossover?
A. Proportioning system
B. O2 analyzer
C. Fail-safe
D. pulse-ox
B. oxygen analyzer
Is the oxygen analyzer located i nthe inspiratory limb or expiratory limb?
inspiratory limb
T/F: the oxygen analyzer can detect a hypoxic mixture caused by a leak in the oxygen flowmeter
True
What is the last line of defense agaisnt a hypoxic mixture?
The oxygen analyzer
What would be some causes of reduced FiO2 during low flow anesthesia?
Sepsis, pai, SNS stimulation, thyrotoxicosis, fever, ect
*average o2 consumption for hte adult is 250ml/min - these situations increase oxygen demand, and can creat a hypoxic mixture during low flow anesthesia
T/F: if there is a suspected pipeline crossover, you should immediately ventilate with an Ambu with the auxillary o2 flowmeter
False!
-turn on your backup tank and d/c the pipeline from the machine
the auxiliarry o2 will be the same o2 supply
What supplies the auxillary o2 on the anesthesia machine?
the pipeline
If theres question of a pipeline crossover- you should re-caliibrate the o2 analzyer
false
worse to assume equipment malfunction and spend time troubleshooting - just assume it’s the real thing and crack open your o2 tank and d/c the pipeline from the machine
The o2 analyzer alarms, you open the o2 tank and d/c the pipeline from the machine…now what ?
verify that the o2 concentration in the circuit is increasing
-once concentration is increasing, conserve tank by using low fllows
- if not, ventilate with an AMBU connected to a different O2 tank
- also get hep to start setting up a TIVA
*reconnect the pipeline ONLY after the supply has been tested
What should be at the top of your differential when the o2 analyzer alarms?
pipeline crossover until proven otherwise
dont assume equpiment malfunction!
T/F: the O2 flush valve delivers a continuous pressure of 35-75psi
FALSE- READ!
35-75L/min
@ 50psi (pipeline pressure)
If your going to hit the o2 flush valve, what resp phase should you hit it in and why
the expiratory phase
-the ventilator spill valve is closed during the inspiratory phase
-pressing the o2 flush during the inspiratory phase transfers this pressure to the patients lungs (risk of barotrauma)
Other than barotrauma, what other issue could occur with excessive use of the o2 flush valve?
awareness
the gas from the o2 flush valve does not pass through the vaporizers and will dilute the partila pressure of the volatile agent and could lead to awareness
T/F: you can use the o2 flush valve for jet ventilation
false- most manufacturers don’t recommend it
but some still do it as “off label” use
Explain drive gas and pneumatic bellows during inspiration and expriation
During inspiration:
-Drive gas flow builds pressure in the chamber, creating a pressure gradient that pushes fresh gas into the lungs
- the increased pressure also closes the spill valve, ensursing vt goes to the pt and not the scavanger
During expiration:
-the drive gas flow stops, intrathroacic pressure builds, and once it exeeds the pressure in the chamber, the patient is able to exhale and refill the bellows
-when the circuit pressure > 2-4cm h20, expired gas is directed through the spill valve to the scavanger
2 functions of the drive gas on a pneumatic ventilator
- compresses belllows
- opens and closes the ventilator spill valve (regulate gas that goes to the scavanger)
What is hte position of the ventilator spill valve during inspiration?
why?
closed
ensures that the tidal volume goes to the patietn and not to the scavenger
What is the minimum expiratory pressure needed to open the ventilator spill valve ?
3cm H20
Select the true statments about the pneumatic ventilator bellows (select 2)
-a descendings bellows is made safer by fresh gas coupling
-a descendings bellow cannot rise and fall with a circuit disconnect
-a leak in the bellows may cause the reading on the o2 analyzer to increase
-a hole in the bellows may caue barotrauma
-a leak in the bellows may cause the reading on the o2 analyzer to increase
-a hole in the bellows may caue barotrauma
a descendings bellows may continue to rise and fall in the event of a circuit disconnect - resh gas decoupling helps solve this problem
Fresh gas flow decoupling vs coupling
decoupling = tv set is what the patient receives
coupling = total Vt = Vt set on vent + FGF during inspiration - volume lost to circuit compliance
Gas inside the bellows = Exhaled tidal volume + what
(vents that couple FGF)
Exhaled tv + FGF during expiration
T/F: the piston ventilator incorporates the resevior bag into the ventilator circuit during mechanical ventilation
True!
I guess this is how you can gell if it’s pneumatic vs piston bellows
since piston ventilators incorprate the resevior bag during ventilation, when would the bag inflate/deflate and why
inflates during inspiration → bc excess fresh gas is diverted into the gag
deflates during expiration
with a piston ventilator, you lose your etco2 and suspect a circuit disconnect- whats something you could look out that would alert you to a circuit disconnect?
the resivor bag - if it’s deflated - there is probably a disconnect (it inflates with inspiration)
so i guess if you lose etco2 and ur bags still inflated, the vent is still delivering breaths but something else is going on - like a bronchospasm or tube migration
Which type of vent has postive and negative pressure relief vales - pneumatic or piston?
piston
when does the postive pressure relief valve open
what type of vent
purpose?
+75cm H20
piston vent
decreases risk of barotrauma (doesn’t eliminate)
when does the negative pressure relief valve open
what type of vent
what happens when it opens?
issue?
-8cm h20
piston
room air is entrained into the breathing circuit to protect agaisnt negative end expriatory pressure
this additional room air can dilute o2 and anesthetic concentrations
why do descending bellows continue to fill during a circuit disconenct?
bc they will entrain room air
T/F: a gas-driven bellow automatically adds 2-3cm of peep
true - due to the design of the ventilator spill valve
T/F: the piston ventilator automaticall y adds 2-3cm of peep
fasle - gas driven vent due to the ventilator spill valve
T/F: in a piston driven vent, if the pt is spontaneously breathing- the breathing bag will not inflate/deflate
true - only inflates/deflates when breaths are delivered by the ventilator
Which statement fregarding PCV is true (select 2):
-The risk of ventilator-associated lung injury is decreased
-increased lung compliance will decrease Vt
-gas flow decelerates during inspiration
-the ventilator switches to expiration after a preset pressure is achieved
- the risk of vent-associated lung injury is decreased
- gas flow decelerates during inspiration
-bc preak pressure is fixed and tidal volume is variable, an increase in lung complicance will increase the Vt
-the vent achieves a peak pressure very early in the inspiratory cycle and holds it for a time determined by the I:E ratio → therefore it does not immediately cycle after the peak pressure is achieved
If your using volume control, what are you watching for cues regarding your patients compliance/degree of anesthesia
what about if your using pressure control?
watching for changes in peak pressures
pressure control- your watching for changes in volumes
In inspiratory flow variable on VCV or PCV?
PCV- initially high to reach preset pressure then slows down to maitnain a cosntant pressure
Which is more effective in reducing the risk of ventilator-associated lung inury - PCV or VCV ?
PCV
Which vent mode would be better for a patient with low compliance?
4 examples
PCV
pregnant, fat, laproscopic surgery, ARDS
Which vent mode would be best if you needed to compensate for a leak with an LMA?
PCV - want to CONTROL the pressure and not go above 20 or you could insulflate the abdomen
Which modes of mechanical ventilation are BEST duited for an LMA? (select 2):
-SIMV
-Inverse ratio ventilation
-PSV
-Controlled mandaroy ventilation
-SIMV and PSV
difference b/t pressure control vs PC with volume guarentee
pressure control- you adjust pressure and see wehre volumes land
PC-VG- guantees a pre-determined tidal volume and will apply the minum pressure required to achoive it
good for compliance changes intraop like laparoscopic surgery
not quite sure how this differs from Volume contorl -you have a preset volume and it applies the minimum pressure required to achieve it
What is SIMV?
A vent mode where you set a TV and RR but it allows the pt to breath spontaenously between machine breathes and the machine will coordinate with the pt breaths to meet the minimum minute ventilation
What does the “pro” in PSV- pro stand for?
protect
-if pt is spontaneously breathing - they will receive PSV
-if they become apneic, the vent will convert to PCV
-when they start spontaneously ventilating, the vent will go back to PSV
Difference between PS, PEEP, CPAP, and BIPAP
PS- only suppports inhalation with set pressure
PEEP- supports exhalation with pressure (keeping alveoli open)
CPAP - supports inhalation and exhalation with the same set pressure (augments inhalation, and reduces airway collapse during expiration)
BIPAP- adjustable CPAP where you can adjust inspiratory pressure support and expiratory pressure support
What is I:E ratio?
it’s how much time a pt spends inhaling vs exhaling
T/F: the risk of assist control ventilation is respiratory alkalosis
True
A/C: vent delivers set Vt and RR but pt can also breathe and if they overbreathe the vent, resp alk
At what pH does ethyl violet change to purple?
a. 7.5
B. 8.6
C. 10.3
D. 12.1
C. 10.3
who the fuck cares - when its purple - change it
The size of co2 absorbent grandules must be between what size?
why?
4-8 mesh
it’s the size found to provide the best balance between absopritive capacity and work of breathing (absorptive capacity and airflow resistance)
Why is it important to turn off your flows between leaving the room?
bc high flows can dry out (dessicate) the soda lime
What is the component in soda lime that is strongly alkaline and irritating to the skin and mucous membranes?
Whats added to provide hardness and minimize dusst production?
sodium hydroxide - the strong base that neutralizes carbon dioxide (an acid)
silica
Soda lime can absorb how much CO2 per 100g of absorbent?
16-26L
prodigy said 14-23 - so i kept 23 in mind as part of my 23 list
apex said specifically 26L
so i feel like if i know 23 - i can at least be close to the answer
T/F- if you notice your soda lime is exhausted and the pts inspired co2 is climbing, you should increase the pt’s minute ventilation
*most manufacturers don’t recommend changing hte absorbent in the middle of the case
False! - your just ventilating the patient more
more ventilation = more co2 into the sodalime thats exhausted already
will worsen your problem
instead- increase the FGF 1-2x the patients minute ventilation
-this converts the circle system into a semi-open one - this shouldp revent rebreathing and the inspired co2 should go down
What % of soda lime granules contain water
13-20%
T/F- all halogenated anesthetics react with soda lime to produce carbon monxide
True
Des > Iso»_space;> Sevo (comound A)
T/F: to reduce carbon monixide build up, we should use low fresh gas flows
True - high FGF will dry it out faster
To reduce the inhalation of compound A (interraction b/t sevo and dessicated soda lime) what should your minimum FGF be for:
-up to 2 MAC hours
-after 2 MAC hours
1-2L/min for up to 2 MAC hours
increase to > 2LPM after 2 MAC hours
Why is potassium hydroxide not used?
bc it dessicates faster, producing higher levels of carbon monixide and compound A
Soda lime equation
- Co2 + H20 = H2Co3
- HCO3 + 2NAOH = Na2CO3 + water + heat
- NaCO3 + Ca(OH)2 = CaOH3 + 2NAOH
carbon dioxide exhaled from pt mixes with water on granules and produces carbonic acid
2. Carbonic acid combines with sodium hydroxide to produce sodium carbonate + water + heat
3. sodium carbonate combines with calcium hydroxide to produce **calcium carbonate and sodium hydroxide **
just remember on each side theres a carbonate (acid) + a hydroxide (base)
and each next step starts with the product of the following
What is Amsorb?
Benifits?
Disadvantages?
Calcium hydroxixde
-weaker base
no CO and no compound A
high cost and low absorptive capcity
Why was baralyme removed from the market?
increased risk of breathing circuit fires when combined with sevoflurane
T/F: exhausted sodalime may revert to a colorless stae wehn the anesthesia machine is not in use
True
doesn’t mean it’s regenerated - the color will return quickly to puprle in the presence of co2
T/F; if your machine has a double chamber absorber, you must replace both canisters at the same time
True
When compared to soda lime, what factor is increased with the use of calcium hydroxide soda lime?
A. Carbon monixide
B. Frequency of replacement
C. CO2 absorption capacity
D. Fire risk
B. frequency of repalcement
it produces less CO
has less absoprtion capcity
and fire risk is with baralyme and sevo
While a patient is ventilating spontaneously with an ETT, you notice that a fresh gas flow of 10L/min is required to fill the breathing bag and determine that the scavenger is malfunctioning. Which statement must be true?
A. The negative pressure reilief valve has failed
B. The positive pressure relief valve has failed
C. There is an open scavenging system
D. There is a passive scavenging system
A. The negative pressure relief valve has failed
What are the five compontents of the scavenger system?
- Gas collection assembly
- Transfer tubing
- Interface (open or closed)
- gas disposal tubing
- gas disposal system
What determines the amount of gas that wremains in the circuit and the amount that is released to the scavenger during:
Spontaneous ventilation vs Mechanical ventilation
Spontaneous ventilation - APL valve
Mechanical ventilation - the ventilator spill valve
Difference between active and passive scavenger systems
vs open an dclosed
active - uses suction to remove waste gas
passive - relys on the positive pressure of the FGF in the system to push the gas out
open- the interface communicates with the operating room envionrment [canister with the ball float]
closed- the interface does not communicate with the OR enivonrment (bag)
Another name for the ventilator spill valve and what does it do
ventiiator relief valve - diverts excess gas inside pts breathing circuit to the scavenger (if pt is being mechanically ventilated)
if breathing spontaneously, APL valve does this
What part of the scavenger contains a resovior for waste gas?
the scavenging interface
b/t open and closed systems- which ones has to be only active and which oen can be active or passive
active only = open
-open systems are open to the room air, suction (active) system are required in order to keep the waste gas in the system and not leak out to the atomosphere and anesthetize everyone
closed systems can be active or passive
which type of system is safer for the patient- an open scavenging system or a closed?
open- bc in the event that the scavenger gets blocked, excess pressure can be released out of the system and itno the enviornment instead of causing barotrauma to the patient
the closed ssytem relys on pressure valves which could be faulty
Which type of scavenger has pressure relief valves in the interface to protect the patient agaisnt extremes of pressure ?
when would each be engaged?
Closed systems
Positive pressure relief valve - prevents barotrauma in the event of scavenger obstruction
negative pressure relief valve (active closed system only) - prevents against excessive suction , which van expose the breathing system to negative pressure leading to hypoxia and NPPE
what type of scavenging interface requires a negative pressure relief valve
closed, active
so just think negatie pressure would occur from too much suction- so it has to be an active system
and whether it’s open or closed – open systems are open to the enviornment to prevent negative pressure - so it has to be a closed system
t/f- open systems can be active or passive
false- closed
open systems ahve tohave suction (active)
t/f- passive systems require a negative pressure relief valve in the scavenging interface
false
passive means no suction
no suction = no negaitve pressure that can b created in the system
Waste gas from the scavenger can go 1 of 2 places ….
- waste gas receptacle
- released into the atmoshphere
max exposure:
halogenated agents alone
nitrous oxide alone
when they are used together?
who makes these guidelines?
halogenated agents </= 2ppm
nitrous </25pp - ALWAYS whether alone or in combo
**halogenated agents </= 0.5ppm when used with nitrous **
OSHA
t/f- an opening scavenging system does not require postive or negative pressure relief valves
True
it’s open to the enviornment so:
too much suction entrains room air into the scavenger
too little suction vents scavenged gas into the OR
T/F- if a passive scavening system is used (not connected to suction) - it MUST have a postive pressure relief valve
true
doesn need a negative pressure valve tho bc no suction
which component scavenger system determines if it’s an open or closed system
the interface
which valves must be present on a closed interface- active scavenger
positive AND negative (passive closed jsut neds negative)
What is the MOST common cause of low circuit pressure?
A. leak in corrugated tubing
B. circuit disconnect
C. incompetent ventilator relief valve
D. improper fitting of co2 absorbent
2nd most common?
B. circuit disconnect
2nd most common = leak around the co2 absorbent
4 things that can alert you to a circuit disconnect:
loss of pressure, volume, etco2
and your observation (no chest rise ,ect)
How should you approach a question that talks about what will detect a circuit disconnect first ? things to consider…
- will the montior alert you in real-time - or is there a delay (anything that eis electronic will have a delay and a longer response time)
- if all the monitors have some degree of delay- which one is the shortest ?
What should you do if the breathing circuit doesn’t hold pressure in the middle of a cprocedure?
grab an ambu and ventilate with the aux o2 , call for extra hands, convert to TIVA
During a general anethetic with ETT, the high peak pressure alarm sounds ; you switch the vent mode to bag mode and the peak pressure returns to baseline . What is the MOST likely explanation for the rise in PIP?
A. failed positive pressure relief valve on the scavenger
B. kinked ett
C. bronchospasm
D. ventilator spill valve malfunctioned
what can you look at before switching?
D. ventilator spill valve malfunctioned
plateu pressure - should be similar to PIP
relief valve on the scavenger would affect both ventilator and spontaneous pt
What is the function of the spill valve
what would happen if it malfunctions
it vents excess fresh gas from the flowmeter to the scavenger
flowmeter or pneumatic bellows?
the fresh gas would have no where to go and a high circuit pressure could result
The transfer tubing joins which components of the scavenger (select 2)
- scavenger interface
- gas disposal assembly
- APL valve
- Gas disposal assembly tubing
APL valve > scavenger interface
the gas disposal assembly tubing connects the scavenging interface othe gas disposal assembly
What is the MIMIMUM amount of pressure when performing a high-pressure leak test on the anesthesia machine
30cm h20
What is hte max flow rate delivered by the o2 flush valve?
75LPM
35-75LPM
50 Psi
Which of the following components creates the GREATEST resistance to airflow?
A. 90 degree elbow
B. Unidirectional valve
C. Endotracheal tube
D. CO@ absorber
C. ETT
Which of the following actions reduce compound A production (Select 2)
- addition of Ca(OH)2
- removal of NaOH
- addition of KOH
- removal of CaCl2
addition of Ca(OH)2
& removal of NaOH
NaOH and KOH are strong bases that act to facilitate the reaction process.
