CABT Patient Monitoring 5 — Questions and Answers
Question 1: Which condition would cause a falsely elevated SpO2 reading on a standard two-wavelength pulse oximeter?
- Carboxyhemoglobin (COHb) poisoning (Correct answer)
- Methemoglobinemia
- Severe anemia
- Hypothermia
Correct answer: Carboxyhemoglobin (COHb) poisoning
Standard pulse oximeters cannot distinguish carboxyhemoglobin from oxyhemoglobin at 660 nm, causing COHb to be misread as oxygenated hemoglobin and falsely elevating SpO2.
Question 2: The 'fast flush test' (square wave test) on an invasive arterial line is performed to assess:
- Dynamic response (natural frequency and damping coefficient) of the fluid-filled monitoring system (Correct answer)
- Accuracy of the zero reference
- Patency of the arterial catheter only
- Calibration of the pressure transducer
Correct answer: Dynamic response (natural frequency and damping coefficient) of the fluid-filled monitoring system
The fast flush test evaluates the dynamic response of the arterial line system by introducing a brief high-pressure flush and observing the oscillatory response pattern on the waveform.
Question 3: A patient's telemetry monitor shows a Mobitz Type II second-degree AV block. The biomedical technician should:
- Immediately notify clinical staff, as this rhythm can progress to complete heart block (Correct answer)
- Reposition the ECG electrodes and recheck
- Document it and monitor for 24 hours before reporting
- Increase the ECG gain setting to improve waveform clarity
Correct answer: Immediately notify clinical staff, as this rhythm can progress to complete heart block
Mobitz Type II block has a high risk of progressing to complete (third-degree) AV block and cardiac arrest, requiring urgent clinical notification.
Question 4: Intracranial pressure (ICP) monitoring via an intraventricular catheter (EVD) is zeroed to the level of the:
- Foramen of Monro (external auditory meatus as surface landmark) (Correct answer)
- Phlebostatic axis
- Lumbar cistern
- Vertex of the skull
Correct answer: Foramen of Monro (external auditory meatus as surface landmark)
ICP is referenced to the level of the foramen of Monro, which is approximated at the bedside by the external auditory meatus (ear canal).
Question 5: Which interference source is most likely to cause an artifact that mimics ventricular fibrillation on an ECG monitor?
- 60 Hz AC interference from a faulty electrode or lead wire (Correct answer)
- Patient talking or coughing
- Low battery in the wireless transmitter
- Use of a non-standard electrode gel
Correct answer: 60 Hz AC interference from a faulty electrode or lead wire
Severe 60 Hz AC interference can produce a coarse, irregular waveform on the ECG that visually resembles ventricular fibrillation, requiring electrode and lead wire inspection.
Question 6: When a temperature probe used for continuous core temperature monitoring reads 2°C higher than a simultaneously taken oral temperature, the most likely cause is:
- Sensor placed in nasopharynx or esophagus measuring true core temperature versus peripheral oral site (Correct answer)
- Probe malfunction requiring replacement
- Patient has a fever
- Incorrect calibration of the oral thermometer
Correct answer: Sensor placed in nasopharynx or esophagus measuring true core temperature versus peripheral oral site
Core temperature sites such as the nasopharynx, esophagus, or pulmonary artery are typically 1–2°C warmer than peripheral sites like the mouth, explaining the difference.
Question 7: The primary function of electrical isolation in patient monitoring equipment is to:
- Prevent dangerous current from flowing through the patient to ground (Correct answer)
- Improve signal-to-noise ratio for ECG
- Reduce electromagnetic emissions from the device
- Extend battery life during portable monitoring
Correct answer: Prevent dangerous current from flowing through the patient to ground
Electrical isolation in patient-applied parts prevents potentially lethal leakage or fault currents from completing a circuit through the patient to electrical ground.
CABT Patient Monitoring 5
Which condition would cause a falsely elevated SpO2 reading on a standard two-wavelength pulse oximeter?