CBET Patient Monitoring Systems 5 — Questions and Answers
Question 1: A BMET is troubleshooting a ventilator patient monitor that shows erratic tidal volume readings. The flow sensor passes bench testing. What is the NEXT most logical step?
- Replace the ventilator circuit entirely
- Inspect the flow sensor for moisture condensation or secretion buildup in-line (Correct answer)
- Recalibrate the SpO2 module
- Check the ETCO2 sampling line for occlusion
Correct answer: Inspect the flow sensor for moisture condensation or secretion buildup in-line
Moisture and secretion buildup inside inline flow sensors is a common cause of erratic volume readings in ventilated patients.
Question 2: What does a pulmonary artery catheter (Swan-Ganz) measure when the balloon is inflated and wedged?
- Right ventricular end-diastolic pressure
- Pulmonary artery occlusion pressure (PAOP), reflecting left heart filling pressure (Correct answer)
- Central venous pressure
- Cardiac output via thermodilution
Correct answer: Pulmonary artery occlusion pressure (PAOP), reflecting left heart filling pressure
When wedged, the inflated balloon occludes forward flow, allowing the distal port to sense pressure that reflects left atrial and left ventricular end-diastolic pressure.
Question 3: A patient monitor's non-invasive blood pressure (NIBP) module consistently reads 20 mmHg higher than manual auscultation. Which factor is MOST likely responsible?
- Cuff bladder is too wide for the patient's arm
- Cuff is undersized relative to the patient's arm circumference (Correct answer)
- The patient has an irregular cardiac rhythm
- The NIBP hose has a small internal leak
Correct answer: Cuff is undersized relative to the patient's arm circumference
An undersized cuff over-compresses peripheral tissue, requiring greater cuff pressure to occlude the artery and producing falsely elevated readings.
Question 4: When zeroing an invasive pressure transducer, the transducer stopcock must be positioned at the phlebostatic axis. Where is this anatomical landmark?
- Level of the right atrium, at the 4th intercostal space mid-axillary line (Correct answer)
- Level of the left ventricle apex
- Level of the aortic valve, at the 2nd intercostal space
- Level of the brachial artery at the antecubital fossa
Correct answer: Level of the right atrium, at the 4th intercostal space mid-axillary line
The phlebostatic axis represents the right atrium level (4th ICS, mid-axillary line) and is the standard external reference for cardiac pressure monitoring.
Question 5: A BMET is setting up a new ECG monitor and must select the correct filter mode. When would you use 'diagnostic mode' rather than 'monitoring mode'?
- During transport to reduce motion artifact
- When accurate ST-segment morphology analysis is required (Correct answer)
- In ICU settings with multiple simultaneous alarms
- When the patient is on a mechanical ventilator
Correct answer: When accurate ST-segment morphology analysis is required
Diagnostic mode uses a wider bandwidth (0.05–150 Hz) to preserve ST-segment morphology, while monitoring mode applies filters that can distort the ST segment.
Question 6: A hospital is evaluating near-infrared spectroscopy (NIRS) cerebral oximetry monitors. Which clinical scenario represents the PRIMARY intended application for these devices?
- Continuous ICU SpO2 monitoring as a backup to pulse oximetry
- Detecting regional cerebral oxygen desaturation during cardiac surgery or carotid endarterectomy (Correct answer)
- Measuring mixed venous oxygen saturation via pulmonary artery catheter
- Assessing peripheral tissue oxygenation in vascular surgery patients
Correct answer: Detecting regional cerebral oxygen desaturation during cardiac surgery or carotid endarterectomy
NIRS cerebral oximetry is primarily used to detect regional cerebral hypoxia during procedures with risk of cerebral ischemia, such as cardiac surgery with cardiopulmonary bypass.
Question 7: A multi-parameter bedside monitor fails electrical safety testing with a chassis leakage current of 750 µA. Per AAMI ES1 standards for patient care equipment, what is the maximum allowable chassis leakage current in normal condition?
- 100 µA
- 300 µA
- 500 µA (Correct answer)
- 1000 µA
Correct answer: 500 µA
AAMI ES1 specifies a maximum chassis (enclosure) leakage current of 500 µA under normal conditions for patient care equipment.
CBET Patient Monitoring Systems 5
A BMET is troubleshooting a ventilator patient monitor that shows erratic tidal volume readings.
The flow sensor passes bench testing.
What is the NEXT most logical step?