EDAIC Anesthetic Equipment and Safety 4 — Questions and Answers
Question 1: Which component of the anesthesia machine is responsible for reducing cylinder pressure from approximately 2000 psi to a safe working pressure of around 45 psi?
- Pressure regulator (reducing valve) (Correct answer)
- Check valve
- Flow control valve
- Pressure relief valve
Correct answer: Pressure regulator (reducing valve)
The pressure regulator (reducing valve) steps down high cylinder pressure to a safe, consistent working pressure of approximately 45 psi for use in the machine.
Question 2: A patient breathing circuit shows persistently elevated CO2 on capnography despite adequate fresh gas flow. The MOST likely cause is:
- Exhausted CO2 absorbent (Correct answer)
- Oxygen analyzer malfunction
- Disconnected oxygen flush valve
- Faulty inspiratory unidirectional valve
Correct answer: Exhausted CO2 absorbent
Exhausted CO2 absorbent loses its capacity to neutralize exhaled CO2, leading to rebreathing and elevated inspired CO2 on capnography.
Question 3: When using a Bain circuit (Mapleson D modification), the recommended fresh gas flow for spontaneously breathing adult patients is approximately:
- 2–3 times minute ventilation (Correct answer)
- 1 L/min above tidal volume
- Equal to tidal volume
- 0.5 times minute ventilation
Correct answer: 2–3 times minute ventilation
For spontaneous ventilation with a Bain circuit, fresh gas flows of 2–3 times the minute ventilation (~150–200 mL/kg/min) are required to prevent rebreathing.
Question 4: The Pin Index Safety System (PISS) on gas cylinders is designed to:
- Prevent accidental connection of wrong gas cylinders to yokes (Correct answer)
- Regulate pressure from the cylinder
- Indicate the remaining volume of gas
- Prevent backflow of gases into the cylinder
Correct answer: Prevent accidental connection of wrong gas cylinders to yokes
PISS uses unique pin configurations for each gas to prevent incorrect cylinders from being mounted on the wrong yoke connection.
Question 5: During anesthesia machine checkout, the 'oxygen flush valve' is tested. What pressure does activating this valve deliver oxygen at?
- 35–75 psi (Correct answer)
- 15–30 psi
- 5–15 psi
- 80–120 psi
Correct answer: 35–75 psi
The oxygen flush valve delivers oxygen directly from pipeline supply at 35–75 psi, bypassing the flowmeters and vaporizer.
Question 6: A rotameter (Thorpe tube) in an anesthesia machine is calibrated for a specific gas because flow readings depend on:
- Gas density and viscosity (Correct answer)
- Gas temperature and pressure only
- Cylinder pressure of the gas
- Color-coding of the flowmeter tube
Correct answer: Gas density and viscosity
Rotameter readings depend on the physical properties (density and viscosity) of the gas, so each flowmeter tube is gas-specific and cannot be interchanged.
Question 7: In a circle breathing system, the purpose of the unidirectional (one-way) valves is to:
- Ensure gas flows in one direction, separating inspiratory and expiratory limbs (Correct answer)
- Prevent oxygen from entering the expiratory limb
- Control the rate of CO2 absorption
- Regulate the APL valve pressure
Correct answer: Ensure gas flows in one direction, separating inspiratory and expiratory limbs
Unidirectional valves in a circle system ensure that gas flows only in the correct direction, keeping fresh gas and exhaled gas separated to prevent rebreathing.
EDAIC Anesthetic Equipment and Safety 4
Which component of the anesthesia machine is responsible for reducing cylinder pressure from approximately 2000 psi to a safe working pressure of around 45 psi?