CBET General Practice 3 — Questions and Answers
Question 1: A pulse oximeter reads 98% SpO2 but the patient appears cyanotic. Which condition MOST likely explains this discrepancy?
- Hypothermia reducing peripheral perfusion
- Carbon monoxide poisoning causing carboxyhemoglobin (Correct answer)
- Anemia with normal oxygen saturation
- Motion artifact from patient tremors
Correct answer: Carbon monoxide poisoning causing carboxyhemoglobin
Pulse oximetry cannot distinguish carboxyhemoglobin from oxyhemoglobin, so CO poisoning produces falsely elevated SpO2 readings despite true hypoxia.
Question 2: The primary purpose of a Faraday cage in a medical imaging suite is to:
- Shield patients from ionizing radiation
- Prevent external RF signals from interfering with MRI signals (Correct answer)
- Ground all electrical equipment simultaneously
- Reduce acoustic noise during MRI scanning
Correct answer: Prevent external RF signals from interfering with MRI signals
A Faraday cage blocks external radiofrequency signals that would interfere with the extremely weak MRI signals being detected.
Question 3: When calibrating a patient scale used for medication dosing, a biomedical technician should use NIST-traceable weights primarily to:
- Save time compared to manufacturer weights
- Ensure measurements are accurate relative to a national standard (Correct answer)
- Satisfy Joint Commission aesthetic requirements
- Avoid purchasing manufacturer-specific calibration kits
Correct answer: Ensure measurements are accurate relative to a national standard
NIST-traceable weights provide an unbroken chain of calibration to national standards, ensuring measurement accuracy and regulatory compliance.
Question 4: In a 3-phase electrical system supplying medical imaging equipment, an open neutral conductor would MOST likely cause:
- Nuisance tripping of circuit breakers
- Overvoltage on some phases damaging connected equipment (Correct answer)
- Reduced power consumption by the equipment
- Increased ground fault current
Correct answer: Overvoltage on some phases damaging connected equipment
An open neutral in a 3-phase system causes voltage imbalance, resulting in overvoltage on some phases that can damage connected equipment.
Question 5: A surgical electrosurgical unit (ESU) causes interference on a nearby patient monitor. The FIRST corrective action should be:
- Replace the patient monitor
- Check and ensure proper placement and contact of the ESU dispersive electrode (Correct answer)
- Install a new ESU with digital output
- Move the patient monitor to a different room
Correct answer: Check and ensure proper placement and contact of the ESU dispersive electrode
Improper dispersive electrode placement causes high-frequency current to seek alternate paths, creating interference in nearby monitoring equipment.
Question 6: Which parameter is checked during an acceptance test for a defibrillator to verify energy delivery accuracy?
- Charge time to maximum energy
- Delivered energy measured with a calibrated defibrillator analyzer (Correct answer)
- Battery voltage at rest
- Electrode impedance in open air
Correct answer: Delivered energy measured with a calibrated defibrillator analyzer
A calibrated defibrillator analyzer measures actual delivered energy into a known load, verifying the device delivers the energy it displays.
Question 7: Which law governs the relationship between pressure, volume, and temperature for an ideal gas, relevant to medical gas cylinders?
- Ohm's Law
- The Combined Gas Law (Boyle's + Charles' Laws) (Correct answer)
- Bernoulli's Principle
- Poiseuille's Law
Correct answer: The Combined Gas Law (Boyle's + Charles' Laws)
The Combined Gas Law (P1V1/T1 = P2V2/T2) describes how pressure, volume, and temperature interrelate in gas cylinders used in medical settings.
CBET General Practice 3
A pulse oximeter reads 98% SpO2 but the patient appears cyanotic.
Which condition MOST likely explains this discrepancy?