NBCRNA Anesthesia Equipment and Technology 2 — Questions and Answers
Question 1: Pulse oximetry measures oxygen saturation using which principle?
- Differential light absorption by oxyhemoglobin and deoxyhemoglobin (Correct answer)
- Transcutaneous oxygen diffusion
- Infrared CO2 analysis
- Polarographic electrode measurement
Correct answer: Differential light absorption by oxyhemoglobin and deoxyhemoglobin
Pulse oximetry uses two wavelengths of light (660 nm red and 940 nm infrared) and Beer-Lambert law to calculate the ratio of oxyhemoglobin to total hemoglobin.
Question 2: Which condition can cause falsely elevated pulse oximetry readings in a patient with carbon monoxide poisoning?
- Carboxyhemoglobin absorbs light similarly to oxyhemoglobin at 660 nm (Correct answer)
- Low perfusion reduces signal accuracy
- Methemoglobin causes a fixed reading of 85%
- Nail polish interferes with both wavelengths equally
Correct answer: Carboxyhemoglobin absorbs light similarly to oxyhemoglobin at 660 nm
Standard pulse oximeters cannot distinguish carboxyhemoglobin from oxyhemoglobin because both absorb red light (660 nm) similarly, leading to falsely high SpO2 readings.
Question 3: The Bain circuit (Mapleson D modification) is a co-axial design where the inner tube carries what?
- Fresh gas flow to the patient end (Correct answer)
- Exhaled gases to the APL valve
- Scavenged gases
- Humidified air
Correct answer: Fresh gas flow to the patient end
In the Bain circuit, the inner tube delivers fresh gas to the patient end while exhaled gases travel through the outer corrugated tube to the APL valve.
Question 4: The anesthesia vaporizer is classified as variable bypass because it does what?
- Splits gas flow between a bypass chamber and a vaporizing chamber (Correct answer)
- Varies temperature to control vapor pressure
- Uses electronic sensors to adjust output
- Relies on carrier gas pressure changes
Correct answer: Splits gas flow between a bypass chamber and a vaporizing chamber
Variable bypass vaporizers split the fresh gas stream — a portion passes through the vaporizing chamber to become saturated with vapor, while the rest bypasses it; the ratio determines the output concentration.
Question 5: When using a laryngeal mask airway (LMA), what is the maximum recommended cuff inflation volume for a size 4 LMA?
- 30 mL (Correct answer)
- 60 mL
- 15 mL
- 50 mL
Correct answer: 30 mL
The size 4 LMA (for adults 50–70 kg) has a maximum recommended cuff inflation volume of 30 mL to achieve a proper seal without excessive pressure.
Question 6: The Venturi effect in anesthesia equipment is used primarily in which device?
- Venturi oxygen mask to entrain room air (Correct answer)
- Circle breathing system CO2 absorber
- Variable bypass vaporizer
- Scavenging system interface
Correct answer: Venturi oxygen mask to entrain room air
Venturi (air-entrainment) oxygen masks use the Bernoulli/Venturi principle to entrain precise amounts of room air, delivering accurate fixed FiO2 concentrations.
NBCRNA Anesthesia Equipment and Technology 2
Pulse oximetry measures oxygen saturation using which principle?