crna 711 oral exam 2024/2025 EXAM QUESTIONS AND
CORRECT ANSWERS ALREADY GRADED A+
PROFESSOR VERIFIED
1. Unidirectional valves: The anesthesia machine has two unidirectional valves
that are disc valves or rubber flap valves.
As inspiration begins, the inspiration valve opens and closes the expiration valve.
This prevents backflow of exhaled gas into the inspiratory limb.
As expiration begins, the expiratory valve opens and closes the inspiratory valve.
This prevents rebreathing of gases in the expiratory limb
The goal is to prevent the rest of circle system from contributing to the circuit dead
space
They need to rapidly open and close
They can be placed wherever as long as each valve is positioned between the
patient and the reservoir bag on each limb.
2. Scavenging system: It is made up of four parts: relief valve, transfer tubing,
scavenging interface, and disposal route
,Relief valve is the APL valve or the vent pressure relief valve. Gases leave via
APL when breathing circuit is used and via vent pressure relief valve when
ventilator is used
Gases then go to the scavenging interface via 19mm or 20 mm conduction tube
that is yellow or purple (specifically this color to prevent errors)
Scavenging interface is between wall suction and breathing circut. It protects high
positive pressure and negative pressure from suction. It is the most important part.
Scavenging waste is done via active or passive routes.
Most scavenging errors are from user error
3. Scavenging system monitoring values: OSHA states that halogenated
gases
cannot exceed 2 ppm (or 0.5 ppm when combined with n20)
Cannot exceed 25 ppm of n20
The goal of the scavenger is to decreases unwanted exposure of the gas
If system is working properly waste gases are reduced 90 percent
4. PISS: Contains 2 5mm pins. These pins vary depending on the gas to ensure
the wrong gas cylinder depending on the machine.
The pin placements also vary
Air is U
O2 is V
N2o is W
5. Pathway of gas through the system: Supply point- fail safe valve (held open
by o2 pressure. If o2 pressure drops N2O will stop too)- flow meters(o2 should
be last)- common manifold- enter the vaporizer- common gas outlet- breathing
circuit- scavenging system- disposed
, 6. Oxygen proportioning system: Prevents hypoxic mixture of gases
O2 and N20 are linked to prevent less than 25 percent o2 delivery
Gears are placed on the two knobs that rotates both knobs as needed
7. O2 tasks: Supply the fresh gas flowmeter
Power the oxygen flush valve
Activate the oxygen low-pressure alarms
Activate the fail-safe mechanism
Drive the ventilator bellows (in gas-driven machines)
8. Oxygen fail safe system: Mechanism that stops all other gases (except air)
from flowing if o2 pressure drops below a threshold. Without this a hypoxic
mixture could be delivered to the patient
There are two methods for this to occur, either the flow of gases will be shut off
completely or some gases will decrease proportionally.
It is important for air to not be shut off because it can be used to drive the bellows
Fail safes do not analyze oxygen content but only pressure. That means if a
crossover happens the system will not be able to detect it.
9. O2 flush valve: This is a valve that rapidly fills the breathing circuit with o2.
When you press it it delivers 35-75 l/min at 50 psi directly to the common gas
outlet. It completely bypasses vaporizer
If you need to fill the bellows it needs to be during expiration is small burts and
never during inspiration it is concaved so it cant be accidently pressed
10. Co2 absorber mesh: Co2 cranuals are 4 to 8 mesh. This means they can
pass through wire strainer with 4-8 wires per in inch.
This value is important because it maximises surface area
CORRECT ANSWERS ALREADY GRADED A+
PROFESSOR VERIFIED
1. Unidirectional valves: The anesthesia machine has two unidirectional valves
that are disc valves or rubber flap valves.
As inspiration begins, the inspiration valve opens and closes the expiration valve.
This prevents backflow of exhaled gas into the inspiratory limb.
As expiration begins, the expiratory valve opens and closes the inspiratory valve.
This prevents rebreathing of gases in the expiratory limb
The goal is to prevent the rest of circle system from contributing to the circuit dead
space
They need to rapidly open and close
They can be placed wherever as long as each valve is positioned between the
patient and the reservoir bag on each limb.
2. Scavenging system: It is made up of four parts: relief valve, transfer tubing,
scavenging interface, and disposal route
,Relief valve is the APL valve or the vent pressure relief valve. Gases leave via
APL when breathing circuit is used and via vent pressure relief valve when
ventilator is used
Gases then go to the scavenging interface via 19mm or 20 mm conduction tube
that is yellow or purple (specifically this color to prevent errors)
Scavenging interface is between wall suction and breathing circut. It protects high
positive pressure and negative pressure from suction. It is the most important part.
Scavenging waste is done via active or passive routes.
Most scavenging errors are from user error
3. Scavenging system monitoring values: OSHA states that halogenated
gases
cannot exceed 2 ppm (or 0.5 ppm when combined with n20)
Cannot exceed 25 ppm of n20
The goal of the scavenger is to decreases unwanted exposure of the gas
If system is working properly waste gases are reduced 90 percent
4. PISS: Contains 2 5mm pins. These pins vary depending on the gas to ensure
the wrong gas cylinder depending on the machine.
The pin placements also vary
Air is U
O2 is V
N2o is W
5. Pathway of gas through the system: Supply point- fail safe valve (held open
by o2 pressure. If o2 pressure drops N2O will stop too)- flow meters(o2 should
be last)- common manifold- enter the vaporizer- common gas outlet- breathing
circuit- scavenging system- disposed
, 6. Oxygen proportioning system: Prevents hypoxic mixture of gases
O2 and N20 are linked to prevent less than 25 percent o2 delivery
Gears are placed on the two knobs that rotates both knobs as needed
7. O2 tasks: Supply the fresh gas flowmeter
Power the oxygen flush valve
Activate the oxygen low-pressure alarms
Activate the fail-safe mechanism
Drive the ventilator bellows (in gas-driven machines)
8. Oxygen fail safe system: Mechanism that stops all other gases (except air)
from flowing if o2 pressure drops below a threshold. Without this a hypoxic
mixture could be delivered to the patient
There are two methods for this to occur, either the flow of gases will be shut off
completely or some gases will decrease proportionally.
It is important for air to not be shut off because it can be used to drive the bellows
Fail safes do not analyze oxygen content but only pressure. That means if a
crossover happens the system will not be able to detect it.
9. O2 flush valve: This is a valve that rapidly fills the breathing circuit with o2.
When you press it it delivers 35-75 l/min at 50 psi directly to the common gas
outlet. It completely bypasses vaporizer
If you need to fill the bellows it needs to be during expiration is small burts and
never during inspiration it is concaved so it cant be accidently pressed
10. Co2 absorber mesh: Co2 cranuals are 4 to 8 mesh. This means they can
pass through wire strainer with 4-8 wires per in inch.
This value is important because it maximises surface area
