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Unit 6: Anesthesia machine Flashcards

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1
Q

What is the pressure system and location of the high pressure system?

A

Pressure system: cylinder pressure
location: begins at cylinder, ends at the cylinder regulators

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2
Q

Components of the High pressure system

A
  • hanger yoke
  • yoke block with check valves
  • cylinder pressure guage
  • cylinder pressure regulators
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3
Q

What is the pressure system and location of the Intermediate system?

A
  • Pressure system: pipeline = 50psi tank = 45psi
  • location: begins at the pipeline and ends at the flowmeter valves
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4
Q

Components of the intermediate pressure system

A
  • pipeline inlets
  • pressure gauges
  • oxygen pressure failure device
  • oxygen second stage regulator
  • oxygen flush valve
  • ventilator power inlet
  • flowmeter valves
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5
Q

Pressure system and the location of the low pressure system

A
  • pressure system: slightly above atmospheric but variable
  • Location: begins at the flowmeter tubes, ends at the common gas outlet
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6
Q

Components of the low pressure system

A
  • Flowmeter tubes (Thorpe tubes)
  • vaporizers
  • check valve (if present)
  • common gas outlet
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7
Q

What is the leak test?

A
  • low pressure leak test (negative pressure test) assess the integrity of the low-pressure circuit from the flowmeter valves to the common gas outlet
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8
Q

How do you perform the low-pressure leak test?

A
  • attach a bulb to the common gas outlet and create negative pressure (-65 cmH2O)
    • the low-pressure system fails if the bulb reinflates within 10 seconds
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9
Q

Make sure these things are done when you perform the low-pressure leak test

A
  • the FGF must be off
  • if there is a minimum FGF when the machine is on - then you need to turn the machine off
  • the vent should be off
  • the vaporizers should be off at frist, but then repeat the test as each vaporizer is turned on
  • perform this test before the first case of the day
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10
Q

What is the high-pressure leak test?

A
  • conducted by closing the APL valve, pressurizing the circuit to 30 cm H2O and observing the airway pressure gauge (pressure should remain constant)
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11
Q

the presence of absence of a check valve determines what?

A
  • the presence or absence of a check valve determines which components of the low-pressure system are tested
  • if a check valve is present, its usually downstream from the vaporizer and upstream from the O2 flush valve
  • the check valve is open in the absence of backpressure and closed when back pressure is applied (i.e. pressing the O2 flush)
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12
Q

SPDD meaning and location of each gas handling component

A
  • Supply: how the gas enters the anesthesia mechine (location: pipeline to the back of the machine)
  • Processing: how the anesthesia machine prepares the gases (location: inside the machine up to the common gas outlet)
  • Delivery: how the gas is brough to the pt (location: breathing circuit)
  • Disposal: how the gases are removed from the circuit (location: scavenging system)
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13
Q

5 tasks of oxygen in the anesthesia machine

A
  1. O2 pressure failure alarm
  2. O2 pressure failure device (failsafe)
  3. O2 flowmeter
  4. O2 flush valve
  5. ventilator drive gas
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14
Q

PISS use

A

prevent use of wrong gas cylinder

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15
Q

O2
liters
PSI
PISS

A

660L
1900 PSI (or 2000psi)
PISS 2,5

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16
Q

Air
liters
PSI
PISS

A

625L
1900 PSI
PISS 1,5

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17
Q

N2O
liters
PSI
PISS

A

1590L
745 PSI
PISS 3,5

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18
Q

DISS

A

prevents wrong gas hose from being attached to the anesthesia machine

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19
Q

Where is the first pressure change in the anesthesia machine?

A

At the DISS system (pressure reducing valve reduces the tank pressure to 45psi before entering the intermediate system)

pipeline pressure 50psi is about the same as in the intermediate system - but since its a smidge higher, this causes the machine to preferentally use the pipeline system over the cylider if the o2 cylinder is accidentally left open

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20
Q

What happens if the pipeline pressure drops?

A
  • If the O2 cylinder is left open, the machine will consume O2 from the cylinder (no alarm will sound b/c the machine doesn’t “know” where the gas is coming from)

When the O2 cylinder is empty, then the failsafe alarm will sound - but your backup supply is already gone!

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21
Q

What form is O2, air, and nitrous in their cylinders?

A
  • O2 = gas
  • air = gas
  • Nitrous oxide = liquid (b/c critical temp is 36 C)
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22
Q

Why does nitrous oxide’s critical temp matter?

A
  • 36 C is slightly above room temp
  • the equilibrium b/t liquid and gas phase produces a partial pressure of 745 mmHg
  • this partial pressure remains constant until all of the liquid is gone
  • when the tank reads empty about 250 L of gas remain in the nitrous tank when no liquid is present
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23
Q

How much nitrous is in the tank when the gauge reads 700 psi?

A

Trick question! weighing the nitrous tank is the ONLY way to determine how much Nitrous is inside the tank

this is because of the lack of pressure - volume relationship

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24
Q

What is critical temperature?

A

the highest temp where a gas can exist as a liquid
* i.e. its the temp above which a gas cannot be liquefied regardless of the pressure applied to it

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25
how to calculate how long your O2 will last based on how much O2 is left in your cylinder:
* tank capacity = 660 L * full tank pressure = 2000psi ## Footnote Boyles law: the pressue inside the cylinder is inversely related to its volume at a constant temp
26
What is the most delacate component of the cylinder?
cylinder valve * if the valve breaks, the cylinder can shoot off like a rocket
27
What should always be between the hander yoke and the cylinder valve?
Washer - this ensures an airtight seal (install a new washer every time you change the cylinder)
28
MRI safe cylinder will have
two colors. most of tank is silver and top of tank is color of gas that it contains. has to be aluminum. ## Footnote most cylinders are ferrous (magnetic)
29
Best way to determine cylinder contents
- read the lable, don't just look at the colors
30
anatomy of the cylinder valve
31
what to do if you open the cylinder and hear a hissing sound
1. tighten connection 2. if that doesn't work, replace washer (gasket) 3. if that doesn't work, use a different cylinder ## Footnote Never ever place more than 1 washer between the cylinder and the hanger yoke assembly. This can bypass the PISS and alloww the wrong cylindfer to be matched up with the wrong hanger yoke
32
what happens if theres no cylinder or yoke plug present and check valve fails
gas that should be going to patient will exit anesthesia machine
33
Fire triad
Oxidixer, fuel and igniter
34
name 2 oxidizers
O2 and nitrous oxide
35
safety relief devices to prevent cylinder explosion include
- fusible plug that melts at elevated temperatures. typically made from woods metal (**bismouth, lead, tin, cadmium**- remember BLT with cheese) - valve that opens at elevated pressurs - frangible disc that ruptures under pressure | Temps higher than 130F or 57C increase risk of fire or explosion
36
role of american society for testing and materials (ASTM)
sets standards for required components of anesthesia machine. standard document is ASTM F1850
37
role of FDA
created 1993 anesthesia machine pre use check out procedures
38
role of OSHA
sets standards for acceptable occupational exposure to volatile anesthetics
39
role of DOT
sets standards for compressed gas cylinders (tests cylinder at 1.66 x PSI) - ex: O2 is 1900 PSI so is tested at 3,154 PSI
40
USDOT requires the following info on the cylinder label (7)
1. government agency (DOT) 2. type of metal used to construct cylinder 3. max filling pressure PSI 4. serial number 5. manufacturer 6. owner 7. date of last inspection
41
What does the O2 pressure failure device measure?
Monitors O2 **pressure** - not concentration
42
which pressure system does the O2 fail safe device reside in
intermediate pressure system
43
two components of the failsafe device in the intermediate pressure system
1. threshold alarm that sounds when O2 pipeline pressure falls between 28-30 PSI 2. pneumatic device that reduces or stops the flow of N2O when the pressure in the O2 tank falls below 20 PSI - less O2 will put less pressure on the spring and then it ultimately blocks flow of N2O
44
2 types of O2 fail safe devices based on machine
1. GE Datex Ohmeda- O2 falls below 20 PSI, N2O flow is not allowed (all or nothing response) 2. Drager- as O2 pipeline pressure decreases, there is a proportionate decrease in N2O flow - flow of N2O is stopped only when O2 pressure is extremely low
45
How can you tell O2 pressure failure device is working?
1. turn on O2 and nitrous 2. make sure backup O2 cylinder is closed, and disconnect the O2 pipeline 3. as you remove the O2 pipeline from the machine, ovserve the flowmeters - the nitrous flow should stop just before the O2 flow stops 4. reintriducing the O2 supply should result in both gases restored to their previous flow rates
46
2 ways the "failsafe" can be tricked
1. O2 pipeline crossover: the failsafe detects **pressure** in the supply line, not the O2 concentration. Therefore, it is not useful for detecting a pipeline crossover 2. flowmeter leak: the failsafe is **upstream** of the flowmeters and therefore wont detect a flowmeter crack where gas can escape
47
the hypoxia prevention safety device on the gas machine will
limit the ratio of N2O to 3x O2 flow (O2 never drops below 25%)
48
compare and contrast O2 pressure failure device with hypoxia prevention safety device
- oxygen pressure failure device: **fail safe device** = shuts off and/or proportionately reduces N2O flow if O2 pressure drops below 20 psi - Hypoxia prevention safety device: **proportioning device** = prevents you from setting a hypoxic mixture with the flow control valves
49
describe link 25 (on GE datex ohmeda)
O2 and N2O flow meter are mechanically linked by a chain -incorporates second stage regulator for N2O and O2 (pneumatic component) -gear engages oxygen to ensure titrated gases adjust as needed
50
O2 ratio monitor controller (Drager)
- O2 and N2O are connected pneumatically - if you adjust the flow control that creates a hypoxic mixture, the supply pressure of the Nitrous will be reduced to maintain the 3:1 ratio
51
when can the proportioning devices not handle a hypoxic mixture?
1. O2 pipeline cross over 2. leaks distal to flow meter valves 3. administration of a third gas (ex helium) 4. defective mechanic or pneumatic components
52
4 types of floats and where is the measurement taken from?
measurement is taken from the widest part of the float
53
describe annular space in flow meter
area between indicator and flow meter wall
54
High flow and low flow affects the oxygen float in what ways?
- High flow: gas flow is orificial and dependent on the gas's dentity.*Diameter of the Thorpe tube exceeds the length of the indicator*. - Low flow: gas flow is laminar and dependent on the gas's velocity. *Length of the indicator exceeds the diameter of the Thorpe tube* ## Footnote The flow (laminar or turbulent) can be predicted by Reynolds' number
55
O2 flow meter position
Positioned closest to the manifold outlet - right aka closest to the patient ## Footnote if a leak developes in any of the other flowmeters, it should not reduce the FiO2 delivered to the pt
56
Reynold's number flow states
Reynolds < 2000 = laminar flow, dependent on peusoilles law (viscosity) reynolds >4000 = turbulent flow, dependent on grahams law (density)
57
equation for reynolds number =
density * diameter * velocity / viscosity
58
how to calculate FiO2
(air flow rate x 21) + (O2 flow rate x 100) / total flow rate | use these actual numbers - not the .21 we are used to
59
how much % O2 delivered through NC for each liter of O2 being administered?
add 4% for each liter of O2 administered up to 44% (6L/min)
60
with fresh gas coupling, what is the equation for total Vt delivered to patient
Vt set on ventilator + FGF during inspiration - volume lost to compliance
61
if using a vent that couples FGF to Vt, name some vent changes that **increase** delivered Vt
decreased RR increased I:E ratio (from 1:2 to 1:1) increased FGF increased bellows height
62
if using a vent that couples FGF to Vt, name some vent changes that **decrease** delivered Vt
increased RR decreased I:E ratio (from 1:2 to 1:3) decreased FGF decreased bellows height
63
if your Vt is set to 600mL, your circuit compliance is 5mL/cmH2O and your peak pressure is 25cmH2O, how much Vt is the patient actually getting?
475mL because 5X25=125 600-125=475
64
Compliance definition
Change in volume for a given change in pressure (measure in distensibility) ## Footnote The gas causing the circuit to expand does not contribute to the Vt the pt is getting. **Many modern vents automatically compensate for fresh gas lost to circuit compliance**
65
The isoflurane dial is set to 2%. What percent of FGF exiting the vaporizing chamber is saturated with isoflurane?
100% - modern variable bypass vaporizers split fresh gas into two parts - some fresh gas enters the vaporizing chamber and becomes 100% saturated with volatile agent - the rest of the fresh gas bypasses the vaporizing chamber and does not pick up any volatile before leaving the vaporizer, two two fractions mix and this determines the final anesthetic concentraiton exiting the vaporizer
66
how the splitting ratio in a variable bypass chamber is determined
Our dial on the vaporizer: - setting a higher number will direct more fresh gas into the vaporizer chamber. - setting a lower number will direct more fresh gas into the bypass chamber
67
how to ensure fresh gas gets 100% saturated with agent when it enters the vaporizing chamber
**flows over** a series of baffles and wicks which increases surface area and turbulence. | ensures 100% saturation ## Footnote Flows less than 200mL/min or greater than 15L/min can lead to reduced vaporizer output
68
what to do if a vaporizer is tipped over
1. drain vaporizer to remove all liquid anesthetic 2. turn dial to highest setting and run high FGF for 20-30m before it can be used on a patient (end tidal amount of agent should decrease to zero
69
____ mL of liquid anesthetic produces about ____ mL of anesthetic vapor at standard temp and pressure
**1 mL** of liquid anesthetic produces about **200 mL** of anesthetic vapor at standard temp and pressure
70
define latent heat of vaporization
number of calories needed to convert 1g of liquid into vapor without a change in temperature | this value is similar for all halogenated anesthetics
71
what is the role of the temperature compensating valve in the variable bypass chamber
adjusts ratio of vaporizing chamber flow too bypass flow and guarantees a constant vaporizer output over a wide range of temperatures. - this device is either a bimetallic strip or an expansion element
72
Is the vaporizer within the circuit or out of circuit?
out-of-circuit
73
define the pumping effect
increases vaporizer output due to things that cause back flow of agent back into the vaporizing chamber. - ex) PPV or the use of an O2 flush valve. - enhanced by low FGF, low concentration dial setting, low levels of liquid anesthetic in vaporizing chamber.
74
Most common location for vaporizer leaks
- loose filler cap *most common* - internal leak in the vaproizer is the most common location for a leak to occur in the low pressure system *a leak can only be detected when the vaporizer is turned on - the vaporizer is functionally removed from the low pressure system when it is turned off*
75
calculate how much liquid anesthetic is used
mL = Vol% x FGF (L/min) x 3
76
vaporizers approved for the use of Des include
- DE datex ohmeda tec 6 - drager D vapor
77
how does tec 6 work
injects a precise amount of agent directly into FGF
78
Problems faced with the Des gas
- much less potent (MAC 6.6) - to achieve the same depth of anesthesia, the absolute volume of des that must be vaporized is higher - heat is carried away by the vaporized molecules - leading to excessive cooling and reduction in vaporizer output
79
How do specific des vaporizers fix the problems associated with des?
Heating and pressurizing the Tech 6 vaporizer to 39C and 2atm
80
does the tec 6 compensate for changes in elevation
no ## Footnote the depth of anestheisa is determined by the partial pressure (not the concentration) of the volatile in the brain
81
in lower ambient pressures (high altitudes), what should you set the dial to for des? in higher ambient pressures (low altitudes), what should you set the dial to for des?
high altitudes (low ambient pressure): increase the setting on the dial low altitudes (high ambient pressures), decrease the setting on the dial
82
required dial setting equation for desflurane =
normal dial setting (% x 760) / ambient pressure in mmHg
83
which device would be the first to detect an O2 pipeline cross over? (and where is it located)
O2 analyzer (which resides in the inspiratory limb of the breathing circuit) ## Footnote last line of defense against a hypoxic mixture
84
3 things an oxygen analyzer monitors
- monitors o2 concentration (not pressure) - can detect an o2 pipdline corssover - can detect a hypoxic mixture causes by a leak in the o2 flowmeter
85
2 types of oxygen analyzers
1. galvanic fuel cell: increasing o2 tension generates a current across 2 electrodes. *Must be claibrated daily*. components are consumable, so must be replaced over time 2. Paramagnetic device: increasing o2 tension creates an increased magnetic attraction. No consumable components. *Faster response time compared to galvanic*
86
if the O2 pipeline supply fails, you must do these 2 crucial steps
turn ON O2 cylinder d/c pipeline O2 supply
87
pressing the O2 flush valve exposes the patient to an O2 flow of __________ and an O2 pressure of __________
O2 flow of 35-75mL/min and 50 PSI (pipeline pressure)
88
the drive gas on a pneumatic ventilator serves two functions
1. compresses the bellows (during inspiration, drive gas flow creates a pressure gradient to push gas towards lungs. during exhalation, drive gas is stopped) 2. drive gas opens and closes ventilator spill valve (during inspiration, drive gas closes spill valve. during exhalation, after circuit pressure exceeds 3cmH2O, spill valve opens and gas exits the scavenger.
89
amount of gas that drives bellows in a pneumatic circuit =
sum of Vt exhaled + FGF during expiration
90
will descending bellows continue to rise and fall with patient disconnect
yeah, the older ones will
91
fresh gas coupling (piston driven ventilator) total Vt delivered to patient =
Vt set on ventilator + FGF during inspiration - small volume lost to compliance
92
if FGF is 10L/min, the RR is 10, the I:E is 1:2 and the Vt=500 on the FGF coupled ventilator, what's the real Vt being delivered to the patient?
500mL/min + 333mL =833mL 10,000mL/min divided by 10 RR = 1000 mL min. I:E is 1:2 which for a 6 second breath (based on RR) is 2/6 seconds or 1/3. 1000 x 1/3 = 333 "fresh gas during I time is added to Vt from I:E"
93
what are the patient implications of a bellow leak
may transmit high gas pressure to the breathing circuit which may cause barotrauma anesthetic vapor could also escape leading to anesthetic awareness bellows uses air or air/O2 mixture- if you are running high FiO2, the FiO2 getting to patient may decrease if theres a bellows leak and O2 is used as ventilator drive gas, FiO2 in breathing circuit may increase
94
will the piston ventilator consume tank O2 in the event of a pipeline failure?
no, but pneumatic may
95
describe two pressure relief valves in piston ventilator
1. positive pressure relief valve opens at 75cmH2O which prevents excessive pressure build up in anesthesia circuit 2. negative pressure relief valve opens at -8cmH2O. when the circuit pressure falls below this value, negative pressure relief valve opens and entrains room air
96
piston ventilators do what to fresh gas
de couple FGF from ventilator!!
97
gas driven bellows ventilators do what to fresh gas
they couple it and Vt relies on FGF!
98
compare and contrast piston ventilator to gas driven bellows vent and PEEP
the piston ventilator does not add PEEP while the gas driven bellows ventilator adds 2-3cmH2O auto PEEP due to design of ventilator spill valve
99
breathing bag and pressure ventilator
-incorporated during MV -deflates during expiration (WEIRD) -bag will not move if patient breathes spontaneously on the ventilator
100
VCV describe Pinsp, PIP, inspiratory flow
Pinsp varies based on compliance if aw resistance rises or compliance decreases, PIP will rise inspiratory flow is held constant during inspiration -fixed Vt, inspiratory flow rate, inspiratory time
101
PCV describe Pinsp, PIP, inspiratory flow
inspiratory flow varies based on compliance. usually uses decelerating pattern. begins high to achieve set inflation pressure then slows down to keep it constant -fixed PIP, inspiratory time
102
things that decrease Vt based on compliance issue or resistance issue
compliance: pneumo, trendelenburg resistance: kinked ETT, bronchospasm
103
things that increase Vt based on resistance change
bronchodilator therapy or removing secretions
104
situations when PCV is better than VCV
low compliance patient (obese, pregnant, lap procedure, ARDS) cant have high PIP (LMA, neonate, emphysema) need to compensate for a leak (LMA, uncuffed ETT in kids)
105
what does an assisted versus controlled versus spontaneous breath look like on the vent
106
if patient initiates breath in AC, do they get pre set Vt
yes they get the Vt that is set
107
describe BiPAP (biphasic positive aw pressure)
pressure #1 inspiratory positive aw pressure (think pressure support for spontaneous breath) pressure #2 expiratory positive aw pressure (think CPAP on exhalation)
108
define APRV (aw pressure release ventilation)
-used for spontaneous ventilation -like BiPAP but there's a high level of CPAP throughout resp cycle -high level pressure is released at pre set intervals to facilitate exhalation -useful in patient with ARDS
109
what is the risk with IRV (inverse ratio ventilation)
breath stacking or dynamic hyperinflation (auto PEEP)
110
all halogenated anesthetics react with soda lime to produce
carbon monoxide (des>iso>sevo)
111
how does compound A get produced
soda lime plus sevo (1-2L/min for up to 2 MAC hours minimum then increase to >2L/min after 2 MAC hours)
112
describe the reaction of carbon dioxide with soda lime
CO2 + H2O = H2CO3 H2CO3 + 2NaOH -->Na2CO3 + 2H2O + heat Na2CO3 + Ca(OH)2 --> CaCO3 + 2NaOH
113
how small versus large granule mesh affects airflow resistance and surface area
small granule: increase air flow resistance and surface area large granule: decrease air flow resistance and surface area
114
2 problems with soda lime that occur
1. absorbent is exhausted and unable to neutralize CO2 (pH >10.3, turns purple) 2. absorbent is desiccated aka too dry
115
what is the best indicator of expired soda lime
presence of inspired CO2 in breathing circuit (remember when soda lime is not in use, it can turn back to white from purple/blue and be deceiving)
116
best thing to do in the middle of the case when you cant change the soda lime
increase FGF to create a semi open system. baseline on capnograph should return to 0
117
methods to minimize risk of carbon monoxide and compound A
-utilize low FGF to preserve water content of soda lime -turn of FGF in between cases -change all absorbents at one time -change canisters if ethyl violet -change canisters if unsure about hydration (FGF left on overnight or something)
118
benefits of silica addition to soda lime
decreases dust and therefore bronchial irritation decreases flow resistance (does reduce efficiency of granules)
119
describe the reaction of CO2 with calcium hydroxide lime (amsorb plus)
CO2 + H2O = H2CO3 H2CO3 + 2Ca(OH)2 --> CaCO2 +2H2O + heat
120
does calcium hydroxide lime contain a strong base? silica?
no, it contains calcium hydroxide to neutralize carbonic anhydrase. calcium chloride keeps it moist calcium sulfate and polyvinylpyrrolidone are used in place of silica to increase hardness
121
benefits of calcium hydroxide lime (amsorb)
1. does not create carbon monoxide 2. little to no compound A production 3. lower risk of fire when compared to soda lime
122
draw backs of calcium hydroxide lime (amsorb)
1. cannot absorb as much CO2 as soda lime (26L per 100g versus 10.6L/100g) 2. therefore, requires replacement more often (and is more expensive)
123
active scavenger system relies on
suction to remove gas (safer for patient but not safer for OR personnel because it communicates with OR environment) -needs negative pressure relief valve to ensure barotrauma does not occur
124
passive scavenger system relies on
positive pressure to remove gas
125
OSHA guidelines exposure to halogenated anesthetics
126
control of FGF going into scavenger: spontaneous ventilation versus mechanical ventilation
spontaneous ventilation: APL valve controls MV: spill valve controls
127
5 components of scavenger system
1. gas collecting assembly (collects waste gas, located at APL and spill valve) 2. transfer tubing (directs gas to interface) 3. interface (open or closed) 4. gas disposal tubing 5. gas disposal system
128
open system interface on scavenging system
can only be used with active systems (connected to suction) no need for positive or negative pressure relief valves removes risk of barotrauma or FGF from breathing circuit too much suction entrains room air in scavenger too little suction vents scavenged gas into OR contains reservoir higher risk of exposing OR personnel to waste gas
129
closed system interface scavenging system
communicates to atmosphere with pressure valves passive system (not connected to suction), must have positive pressure relief since there is no suction, will not remove excess gas from circuit if an active system is used, must have positive and negative pressure relief contains a reservoir
130
4 ways to monitor for circuit disconnect
pressure, volume, EtCO2, vigilance (nothing electronic, like O2 analyzer, is mentioned because it is electronic and will alert on a delay versus real time)
131
high pressure system location and components
begins at cylinder, ends at cylinder regulators components: hanger yoke, yoke block with check valves, cylinder pressure gauge, cylinder pressure regulators
132
intermediate pressure system location and components
begins at pipeline, ends at flow meter valves. components: pipeline inlets, pressure gauges, oxygen pressure failure device, oxygen second stage regulator, oxygen flush valve, ventilator power inlet, flow meter valves
133
low pressure systems, locations, components
begins at flow meter tubes, ends at common gas outlet components: flowmeter tubes (thorpe tubes), vaporizers, check valve (if present), common gas outlet.
134
intermediate pressure system pipeline and tank PSI
pipeline= 50 PSI tank= 45 PSI
135
SPDD
supply (cylinder) processing (vaporizor) delivery (circle system) disposal (scavender)
136
5 tasks of O2 in anesthesia machine
1. O2 pressure alarm 2. O2 pressure device 3. O2 flow meter 4. O2 flush valve 5. ventilator drive gas
137
piston ventilator considerations
more accurate Vt uncoupled from FGF doesnt use tank O2 (because it doesnt use it as a bellows drive gas) artificial sound can mimic bellow ventilator
138
high pressure system begins and ends at includes
begins at cylinder, ends at cylinder regulators includes hanger yoke, yoke block with check valves, cylinder pressure gauge, cylinder pressure regulators
139
intermediate pressure system begins and ends at includes
begins at pipeline, ends at flow meter valves includes pipeline inlets, pressure gauges, oxygen pressure failure device, oxygen second stage regulator, O2 flush valve, ventilator power inlet, flowmeter valves
140
low pressure system begins and ends at includes
begins at flow meter tubes, ends at common gas outlet flow meter tubes (thorpe tubes) vaporizers check valve (if present) common gas outlet
141
142
the bourdon pressure gauge on an O2 cylinder reads 500 PSI. how long will the tank last if youre administering 2L/min
75 (or 83 or 87 depending on liters of O2)
143
O2 fail safe device resides in which pressure system
intermediate
144
minimum FiO2 permitted by a proportioning device
25%
145
closed system interface scavenging system
communicates to atmosphere with pressure valves passive system (not connected to suction), must have positive pressure relief since there is no suction, will not remove excess gas from circuit if an active system is used, must have positive and negative pressure relief contains a reservoir
APEX... FML
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