Anesthesia Machine Flashcards
Intermediate pressure begins at ___ and ends at ___
begins at pipeline inlet and ends at the flowmeter control valves
Low pressure system begins at and ends at
begins at thorpe tubes and ends at the common gas outlet
PISS configurations
Air = 1 and 5 O2 = 2 and 5 Nitrous = 3 and 5
What is the most delicate part of the cylinder
The cylinder valve
What do MRI compatible cylinders look like?
Mostly metallic with a strip of color indicating the gas
Cylinders should not be exposed to temps above
130F (57C)
Temps above this can cause fire or explosion
O2 pressure failure device will activate when
O2 pressure is
O2 pressure failure device is also called the
Failsafe device
It is safe, because it protects against failed O2 pressure
Purpose of the O2 pressure failure device (Failsafe device)
Detects and protects against low O2 pressure (once less than 30psi).
This also reduces or stops the flow of nitrous to protect against hypoxic mixtures! Will either reduce flow or stop completely.
What does it mean if the O2 pressure failure device goes off?
Low O2 pressure (
What pressure system is the O2 pressure failure device (failsafe device) located
Intermediate pressure system
All gases besides ____ pass a failsafe device
All gases other than O2. This is to protect against hypoxic mixtures
The device that keeps N20 and O2 ratio at 3:1 is called
Hypoxia prevention safety device
This is either pneumatic or a chain linked system
This is a proportioning device. Prevents you from setting a hypoxic mixture at the levels of the flowmeter valves.
What is the annular space?
Space between the widest part of the float and the thorpe tube. Because the tube is narrowest at the base and widest at the top, this also means that the annular space is widest at the top. This variable orifice architecture provides a constant gas pressure throughout a wide range of flow rates.
Laminar flow is dependent on gas ____
Turbulent flow is dependent on gas ____
Laminar flow depends on gas viscosity
Turbulent flow depends on gas density
This is the most delicate part of the anesthesia machine
Flowmeters, because they’re made of glass. If any component of the flowmeter is damaged, the ENTIRE UNIT must be replaced.
Flows less than ____ or more than ____ can lead to reduced vaporizer output (i.e.- the gas moving through the vaporizer may not become 100% saturated)
less than 200mL/min
or
greater than 15L/min
Pumping effect
Occurs when gas that has already left the vaporizer re-enters the vaporizer. Usually happens d/t PPV or use of O2 flush.
Also more at risk with low flows, low concentration setting on dial, and low levels of liquid anesthetic in the chamber.
Modern design minimizes pumping effect.
TEC 6 heats to what temp?
39C
Effect of elevation on vaporizers
Conventional variable bypass vaporizers are not affected by changes in elevation.
TEC6 does NOT compensate for changes in elevation.
Are anesthesia vaporizers in the circuit or out of circuit?
They are out of circuit
Most common cause of low circuit pressure
Disconnect at the Y piece. If this is not an choice, then CO2 canister is the next best option.
O2 consumption in the average adult is ___mL/min
250mL/min
What to do in the event of an O2 pipeline crossover
Open the O2 tank and disconnect the pipeline
Pressing the O2 flush on (inspiration/expiration) can lead to barotrauma
can lead to barotrauma on INSPIRATION
Relationship between the drive gas and the spill valve
The drive gas is what opens and closes the spill valve.
On inspiration, the drive gas CLOSES the spill valve. This way, the drive gas is driving air into the lungs only and not lungs/scavenging.
On exhalation, the drive gas stops. Exhaled volume fills the bellows first. Once pressure in the circuit exceeds 3cmH2O, the spill valve opens and excess gas goes to scavenging. This explains the intrinsic PEEP in pneumatic ventilators.
FGF is continuously being added to the circuit. The amount of air going to the bellows is the sum of TV + flowmeter flow during exhalation.
What happens with O2 flush?
O2 is delivered right from the pipeline. So, 50psi and 35-75L/min.
This does NOT go through the vaporizer, and leads to dilution.
How many relief valves are in the piston ventilator?
2
One for positive pressure relief and one for negative pressure. Positive opens at 75, negative opens at -8.
What happens to the breathing bag with piston ventilators?
The bag is incorporated into the vent circuit. So the bag inflates on inspiration and deflates on expiration.
Is soda line an acid or base?
It’s a strong base. Remember the catalyst is NaOH.
Ethyl violet in soda lime turns from gray to blue-purple once it falls below what pH?
10.3
How hydrated is soda lime normally?
13-20% by weight
Remember this water is needed in the first step of the soda lime reaction
What Vas cause CO production with desiccated soda lime?
Des > iso»_space;»»»sevo
This is the most unstable halogenated anesthetic in soda lime
Sevo.
It’s unstable in BOTH hydrated and desiccated soda lime
CO2 absorbent capacity of soda lime vs. calcium hydroxide lime (Amsorb)
Soda lime = 26L CO2/100g
Amsorb = 10.6L CO2/100g
OSHA gas concentrations in the OR
Nitrous alone
2 common conditions that result in rebreathing CO2
1) CO2 absorbent exhaustion
2) Incompetent unidirectional valve
Maplesons that are best and worst for spontaneously breathing pts
A is best
B is worst
(A>DFE>CB)
This is the best monitor you have to determine if your FGF is high enough with a mapleson
EtCO2
These maplesons are best and worst for controlled ventilation
D is best
A is worst
This mapleson does not have an APL valve OR reservoir bag
E
also called Ayre’s T Piece
FGF should be _____x MV for maplesons
2.5x your minute ventilation
Exception is Mapleson A, which requires FGF 20x MV during controlled ventilation!
This circuit is good for preventing heat loss
Bain Circuit
This mapleson is also called Jackson-Rees
F
This test is used to identify kinking of the FG hose in the Bain circuit
Pethick’s Test
Bain circuit is a modified Mapleson ____
D
How to perform the Pethick’s Test
1) Occlude the elbow at the patient’s end of the circuit
2) Close the APL
3) Use the O2 flush to fill the circuit
4) Remove the occlusion from the end of the elbow while flushing the circuit
If the reservoir bag collapses from the Venturi effect, the Bain is good to use
If the bag remains inflated, the inner tubing is occluded and the circuit should be discarded.
