anesthesia machine Flashcards
what is the pipeline pressure
50 psi
what is the tank pressure
45 psi
how to test low pressure system
attach bulb to CGO- create negative pressure- test fails if bulb reinflates within 10 sec
high pressure leak test
close APL, pressurize circuit to 30- observe pressure gauge- pressure should remain constant
what is the SPDD model
supply: how gas enters the machine
processing: how the anesthesia machine prepares the gas (up to CGO)
delivery: how prepared gases are brought to the patient
disposal: how gases are removed from the circuit (scavenging)
5 tasks of oxygen
o2 pressure alarm
o2 pressure failure device
o2 flowmeter
o2 flush
ventilator drive gas
what is the pin index safety system
-prevents inadvertant misconnection of gas cylinders
-pin configuration on each hanger yoke- diff for each gas
-o2 pressure drops to 45 psi when it enters entry into intermediate system
how can the PISS be bypassed
the prescence of more than one washer between hanger yoke assembly and tank allows PISS to be bypassed
diameter index safety system
prevents inadvertent misconnections of gas hoses. each gas hose and connector are sized and threaded for each gas
what is the pipeline pressure
50 psi (same as intermediate)
how do you tell cylinder content
by LABEL not color
how many L and psi are in oxygen
660 L , 1900 psi
how many L and psi are in air
625 L and 1900 psi
how many L and psi are in n2o
1590 L and 745 psi
what law is used to calculate cylinders content
boyles
how does n2o exist in the tank
as a liquid unless it is almost empty
what is the pressure of the gas n2o above liquid
remains constant at 745 psi regardless of how much liquid is in the tank
what is the critical temp of n2o
36.5 (above room temp 20 degrees c)
what is the most sensitive part of the gas cylinder
cylinder valve
what to do if you suspect a leak in the cylinder
-tighten the connection
-replace washer between cylinder and hanger yoke
-change cylinder
-if you dont have replacement cylinder: insert yoke plug- if valve fails and there is no cylinder/ yoke plug- gas should be going to pt will exit here
what cylinders are MRI safe
aluminum. 2 colors: silver tank and color on top
what is the oxygen pressure failure device (failsafe)
-monitors for low o2 pressure in the anesthesia machine
-alarms in the event of depleted o2 tank, drop in pipeline pressure or disconnected o2 hose
-does NOT alarm in the setting of pipeline crossover (measures pressure, not o2 concentration!!!)
is in intermediate pressure system: alarms when pressure is below 28-30 psi
will stop n2o when pressure is below 20
hypoxic prevention safety device
-prevents a hypoxic pressure
-fio2 should never drop below 25% (3:1 ratio)
when will the hypoxic prevention safety device alarm
-o2 pipeline crossover
-leaks distal to flowmeter valves
-administration of a 3rd gas
-defective mechanic/ pneumatic components
what begins the low pressure system
flow meters
where should the o2 flowmeter be positioned
CLOSEST to CGO
reynolds number
laminar <2000
turbulent >4000
transitional 2-4000
when is laminar flow favored
low FGF
higher FGF annular space acts like an orfice creating turbulent flow pattern
what is fresh gas coupling
coupling of FGF to the tidal volume set on the ventilator may lead to errors in predicted Vt and MV (really only seen with older anesthesia machines)
what is the tidal volume given to the patient during fresh gas coupling
tidal volume delivered to patient= Vt set on the ventilator + FGF during inspiatrion- volume lost to circuit compliance
in flow coupled anesthesia machines, changes in RR, I:E ratio, FGF and height of the bellows impact total Vt given to pt
if machine does not couple FGF to Vt, then what is set on ventilator is what gets delivered to patient
what is circuit compliance
a chance in volume for a given change in pressure- measure of distensibility
do modern ventilators compensate for fresh gas lost to circuit compliance
yes- when ventilator produces positibe pressure inside breathing circuit some of the gas causes circuit to expand. the quality of gas does not reach the patient and does not contribute to vt pateint recieeves. not an issue now
what is variable bypass
when FG enters vaporizer- some encounters liquid anesthetic- the rest bypasses the anesthetic.
the concentration set on the dial determines the splitting ratio.
before leaving the vaporizer the 2 fractions mix- determines final anesthetic concentration to the patient
what is flow over?
as fresh gas enters the vaporizing chamber (liquid anesthetic is here)- it flows over a series of baffles and wicks.
what do you do if a vaporizer tipped over
run on high FGF for 20-30 mins before using on pt. some liquid anesthetic may enter bypass chamber
temp compensated
the valve adjusts ratio of vaporizing chamber flow to bypass flow and guarantees a constant vaporizer output a wide range of temps
what does out of circuit mean
the variable bypass vaporizer is positioned outside the breathing circuit
what does agent specific mean
each vaporizer is calibrated to one anesthetic agent
how does tec 6 vaporizer work
injects a precise amount of des directly into FGF
what temp does des heat up to
39 c and presurizes it to 2 atm
what is des vaport pressure
3-4 x higher than those of the other agents
why cant you use a normal vaporizer with des
boils just above room temp (22 C)
tec 6 and changes in elevation
does NOT compensate- important b/c depth of anesthesia is determined by partial pressure NOT concentration
higher altitude with tec 6->
higher setting on dial
hyperbarbaric oxygen tank and tec 6->
lower setting on dial
what is the oxygen analyzer
-typically resides in the inspiratory limb
-final defense against hypoxic mixture!!!!
what is the only safety device that measures o2 concentration
oxygen analyzer
can detect pipeline crossover and hypoxic mixture due to a leak in flowmeter
