14. Adv Anesthesia Machine Flashcards
vaporizer dial percentage
the percent of agent in the fresh gas flow
3% vaporizer dial
3% of the FGF will be VA
97% O2
3% agent
vaporizer chambers for volatile agents will produce
vapor pressure
which volatile agent has the highest vapor pressure
Des
which volatile agent has a lower poiling point
Des
rank the inhalational agent vapor pressure from highest to lowest
HIGHEST
Nitrous
Des
Iso
Sevo
LOWEST
latent heat of vaporization
heat released as the liquid turns into vapor
what is unique about Des’ vaporizer
it is pressurized
and heated
prolong usage of Nitrous from a tank can cause
ice crystallization on the cylinder
Sevo/Iso vaporizer type
variable bypass vaporizer
variable bypass vaproizer
some FGF goes into the vaporizer while most of it bypasses the vaporizer
condensation
converting gas to liquid
what makes condensation easier
cooling
pressurizing
critical temperature
the temp at which a gas becomes cold enough to liquify
below critical temp
gas CAN be liquified by pressure
above critical temp
gas CANNOT be liquified by pressure
O2 critical temp
-119C
Air critical temp
-140.6C
Nitrous Oxide critical temp
36.5C
gasses with lower critical temps are ________ to liquify
gasses with lower critical temps are harder to liquify
ideal gas laws
P/V = P/V
ideal gases
O2
N2
Air is a mix of N2 and O2
what temp do hospitals store bulk O2 in?
-183C
typically liquid
air
21% O2
79% N2
is nitrous oxide an ideal gas
No
what state is nitrous found in the E cyclinder?
liquid and gas
has vapor pressure
full tank of O2
2000 psi
660 L
full tank of N2O
750 psi
1590 L
the N2O tank will have liquid in it as long as it is ______ % full
the N2O tank will have liquid in it as long as it is 25% full
once the N2O tank is ______% depleted, it will exist entirely in ______ form
once the N2O tank is 75% depleted, it will exist entirely in the gas form
when does the pressure in the N2O tank begin to drop
once all the liquid is depleted (75% depleted)
at what volume will the N2O tank begin to drop pressure?
<400L left in tank
O2 gas tank color: USA
Green
O2 gas tank color: ISO
White
N2O gas tank color: USA and ISO
light blue
Air tank color: USA
yellow
Air tank color: ISO
black and white
suction color: USA
white
suction color: ISO
yello
N2 tank color: USA/ISO
black
CO2 tank color: USA/ISO
grey
Helium tank color: USA/ISO
brown
safety features of VA
- color coded
- safety interlock
- keyed adapters
sevo color
yello
iso color
purpple
des color
blue
safety interlock system
one vaporizer can be turned on at a time
what would happen if you put Des in Sevo vaporizer?
overdose
Des has 4x vapor pressure of sevo
what would happen if you put Sevo in Des vaporizer?
underdose
Sevo has 4x less vapor pressure than des
max limit of N2O allowed in OR
25 PPM
max limit of VA allowed in OR: alone
2 PPM
max limit of VA allowed in OR: w/25 PPM nitrous
0.5 PPM
thorpe tube flowmeter
bobbin
tapered tube
which side of the thorpe tube is wider
top of tube is wide
bottom of tube is narrow
why is O2 furthest downstream from N2O and air?
prevents hypoxic mixture of gas from being delivered to pt in case of leak
compliance
ability of container to expand when pressure is added to it
low compliance
will not expand easily
high compliance
will expand easily
compliance def
how much the volume of a container changes per unit of pressure added
pulmonary compliance eq
pulm compliance = change in volume (mL) / change in pressure (cmH2O)
higher volume change
higher compliance
lower volume change
lower compliance
elastic recoil
ability of container to return to original volume after the pressure inside the container is released
low elasticity
deflate slowly
high elasticity
deflate quickly
elasticity and compliance relationship
inversely proportional
compliant lung
expand well
deflate slowly
air trapping
COPD/smoking
non-compliant (restrictive) lung
hard to get air in
easy to exhale
acute respiratory disress syndrom
PIP is aka
dynamic compliance
plateau pressure aka
static compliance
spirometer location
in front of expiratory valve
spirometer measures
exhaled tidal volumes
spectrometer analyzes
which gases
In tidal
en tidal
O2 analyzer
FiO2 (in tidal O2)
fail safe valve
prevents accidental overdose of N2O
fail safe valve sense
decrease in O2 wall pressure
when does the fail safe valve close?
if O2 supply falls below 25 psi
check valve location
before common gas outlet
check valve
prevents PPV from backing up into the vaporizers and flowmeters
PPV backflow could
change inhaled anesthetic concentration
cause inaccurate flowmeter readings
false positive
indicates presence of problem even though no problem exists
high false positive rate
higher chance of alarm being incorrect
false negative
no alarm
indicates no problem even though a problem exists
false negative examples
pulseless electrical activity (PEA)
CO poisoning (pulse ox)
high sensitivity
high false positive rate
low false negative rate
high specificity
low false positive rate
high false negative rate
sensitivity and specificity relationship
inversely proportional
O2 supply failure alarm triggers at
<30psi
indicates fail safe valve is close to closing
low inspire O2 alarm triggered by
low FiO2
high circuit pressure alarm triggers
kinked ETT
weight against diaphragm (obese, Tberg, lap)
light anesthesia (bronchospasm, coughing)
sustained airway pressure alarm triggers
continuous increase in circuit pressure
APL valve is too closed
scavenging is blocked
low circuit pressure alarm triggers
large circuit leak
(disconnected circuit)
older machine differences
visible ventilator bellows
ventilator powered by high pressure O2 pathway (no electrical power needed)
in vent mode, breathing bag independent of circuit
fresh gas coupling
leak in older machine bellows could cause
higher than expected PIP
higher than expected FiO2
descending bellows
descend when filling with FGF
ascend when giving breath
hard to diagnose circuit leak
ascending bellows
ascend when filling w/FGF
descend when giving breath
easier to diagnose circuit leak
fresh gas coupling
FGF from flowmeters adds extra volume to tidal volume being delivered by vent
tidal volumes increase as FGF increases
ventilator decoupling
FGF rate does not affect tidal volume
feature on newer machines
increase dead space
increases airway resistance
decreasing radius/diameter of circuit
increases circuit resistance
what has a greater impact on resistance?
diameter/radius > length
how do you decr circuit resistance
shorten circuit volume
incr diameter of circuit/breathing tube
tidal volume is lost to the ______ of the circuit
tidal volume is lost to the compliance of the circuit
