CBET - Certified Biomedical Equipment Technician Patient Monitoring Systems Questions and Answers 1 — Questions and Answers
Question 1: A nurse reports that an ECG waveform on a patient monitor shows a thick, fuzzy baseline, consistent across all leads. The patient is calm and still. Which of the following is the MOST likely cause of this 60 Hz interference artifact?
- Patient shivering or muscle tremors.
- A detached right leg (reference) electrode.
- Improper grounding of the monitor or another nearby electrical device. (Correct answer)
- The ECG gain setting being too high.
Correct answer: Improper grounding of the monitor or another nearby electrical device.
A thick, regular, fuzzy baseline is characteristic of 60 Hz (or 50 Hz in some regions) AC electrical interference. This noise is introduced from nearby power lines or equipment and is most often caused by improper grounding of the patient monitor or another electrical device in the patient's vicinity. Patient tremors cause irregular, jagged artifacts, while a detached reference lead often results in a wandering baseline or complete loss of signal. High gain would amplify the existing signal and noise but is not the root cause of the 60 Hz interference itself.
Question 2: A pulse oximeter (SpO2) determines a patient's oxygen saturation level by measuring the differential absorption of what?
- Red and infrared light by arterial blood. (Correct answer)
- Blue and green light by venous blood.
- Ultrasonic waves reflected by red blood cells.
- The electrical impedance of blood flow in the capillaries.
Correct answer: Red and infrared light by arterial blood.
Pulse oximetry works on the principle of spectrophotometry. The probe emits both red (approx. 660 nm) and infrared (approx. 940 nm) light through a pulsating arterial blood bed. Oxygenated hemoglobin and deoxygenated hemoglobin absorb these two wavelengths of light differently. The monitor analyzes the ratio of the light absorbed during the arterial pulsation to calculate the oxygen saturation (SpO2).
Question 3: A BMET is called to check a patient monitor that repeatedly alarms for "NIBP Overpressure" and fails to provide a reading. The technician has already verified the cuff is the correct size for the patient. What is the MOST likely cause of this issue?
- A leak in the NIBP cuff or hose.
- A blockage or kink in the NIBP hose between the monitor and the cuff. (Correct answer)
- The NIBP pump is weak and failing.
- The monitor's software requires an update.
Correct answer: A blockage or kink in the NIBP hose between the monitor and the cuff.
An "Overpressure" alarm typically occurs when the system's pressure safety limit is exceeded during inflation. This is most often caused by an occlusion or blockage in the pneumatic pathway, such as a kinked hose. The pump continues to push air, but the blockage prevents the cuff from inflating, causing pressure to build up rapidly in the hose near the monitor's sensor. A leak would cause a "Cuff Leak" or "Unable to Inflate" alarm. A weak pump would likely fail to inflate the cuff to the target pressure, also resulting in a different error.
Question 4: Which of the following is a critical step that must be performed by the clinical staff before using an invasive blood pressure (IBP) monitoring setup to ensure accurate readings?
- Applying conductive gel to the transducer.
- Entering the patient's age and weight into the monitor.
- Selecting the correct size NIBP cuff.
- Opening the transducer to atmospheric pressure and performing a "zero." (Correct answer)
Correct answer: Opening the transducer to atmospheric pressure and performing a "zero."
To ensure accuracy, an invasive pressure transducer must be referenced to atmospheric pressure. This process, known as "zeroing," involves opening a stopcock to vent the transducer to the open air and then pressing the zero button on the monitor. This establishes a baseline of zero, so that all subsequent measurements reflect the patient's pressure relative to the atmosphere. The other options are incorrect procedures or are irrelevant to IBP monitoring.
Question 5: Most modern patient monitors measure respiration rate using a technique called impedance pneumography. How is this measurement obtained?
- A thermistor near the nose and mouth measures airflow temperature changes.
- A small, high-frequency current is passed between two ECG electrodes, and the change in thoracic impedance is measured. (Correct answer)
- A microphone on the patient's chest detects breathing sounds.
- An SpO2 sensor detects small variations in the plethysmographic waveform.
Correct answer: A small, high-frequency current is passed between two ECG electrodes, and the change in thoracic impedance is measured.
Impedance pneumography utilizes two of the standard ECG electrodes. A safe, high-frequency, low-amplitude current is passed through the patient's thorax. As the patient inhales and exhales, the volume of air in the lungs changes, which causes a corresponding change in the electrical impedance of the chest cavity. The monitor detects these cyclical impedance changes and calculates the respiration rate from them.
Question 6: When comparing mainstream and sidestream capnography, which of the following is a primary advantage of the mainstream method?
- It provides a faster response time with a more distinct waveform. (Correct answer)
- It is less susceptible to being clogged by patient secretions.
- It uses a disposable sampling line, reducing cleaning requirements.
- It does not add any weight or bulk to the patient's breathing circuit.
Correct answer: It provides a faster response time with a more distinct waveform.
Mainstream capnography places the CO2 sensor directly in the patient's breathing circuit, allowing for instantaneous measurement of exhaled gas. This results in a faster response time and a sharper, more accurate waveform compared to sidestream, which must pull a gas sample through a tube to a remote sensor, introducing a time delay. The disadvantages of mainstream are its added weight at the airway and potential for clogging, while the disposable sampling line is a feature of sidestream.
CBET - Certified Biomedical Equipment Technician Patient Monitoring Systems Questions and Answers 1
A nurse reports that an ECG waveform on a patient monitor shows a thick, fuzzy baseline, consistent across all leads.
The patient is calm and still.
Which of the following is the MOST likely cause of this 60 Hz interference artifact?