CBET Medical Equipment Function 2 — Questions and Answers
Question 1: What principle does an ultrasound imaging system use to create images of internal body structures?
- Ionizing radiation absorption
- Piezoelectric transducer emitting and receiving high-frequency sound waves (Correct answer)
- Magnetic resonance of hydrogen atoms
- Infrared thermal detection
Correct answer: Piezoelectric transducer emitting and receiving high-frequency sound waves
Ultrasound uses piezoelectric transducers to emit high-frequency sound waves and detect reflected echoes to create real-time images.
Piezoelectric crystals convert electrical signals to mechanical vibrations at 2-18 MHz. Echo amplitude determines pixel brightness (B-mode imaging). Biomedical technicians test image quality with phantoms.
Question 2: In a mechanical ventilator, what is the function of the PEEP (Positive End-Expiratory Pressure) valve?
- To regulate oxygen concentration
- To maintain positive pressure in the airways at the end of exhalation, preventing alveolar collapse (Correct answer)
- To measure tidal volume
- To trigger the next breath cycle
Correct answer: To maintain positive pressure in the airways at the end of exhalation, preventing alveolar collapse
The PEEP valve maintains positive pressure at end-exhalation, preventing alveoli from collapsing and improving oxygenation.
Biomedical technicians must verify PEEP accuracy during PM using a calibrated manometer. Testing includes verifying PEEP at multiple settings and ensuring no PEEP is present when set to zero.
Question 3: What type of pump mechanism do most volumetric IV infusion pumps use to deliver fluids?
- Centrifugal pump
- Peristaltic pump mechanism that sequentially compresses IV tubing (Correct answer)
- Gear pump
- Diaphragm pump
Correct answer: Peristaltic pump mechanism that sequentially compresses IV tubing
Most volumetric IV infusion pumps use a peristaltic mechanism that sequentially compresses the tubing to push fluid forward.
Only manufacturer-specified tubing sets should be used as tubing compliance affects accuracy. PM testing includes flow rate accuracy, occlusion alarm testing, air-in-line detector sensitivity, and free-flow protection verification.
Question 4: How does a pulse oximeter differentiate between oxygenated and deoxygenated hemoglobin?
- By measuring blood pressure changes
- By comparing absorption of red (660nm) and infrared (940nm) light wavelengths through tissue (Correct answer)
- By analyzing exhaled carbon dioxide
- By measuring skin temperature changes
Correct answer: By comparing absorption of red (660nm) and infrared (940nm) light wavelengths through tissue
Pulse oximeters use two wavelengths because oxyhemoglobin and deoxyhemoglobin absorb them differently.
Limitations include poor perfusion, motion artifact, ambient light interference, carboxyhemoglobin (reads falsely high), and methemoglobin (reads approximately 85%).
Question 5: What is the primary function of a defibrillator's capacitor?
- To regulate the charging voltage
- To store electrical energy that is rapidly discharged through the patient's chest to restore normal heart rhythm (Correct answer)
- To filter the incoming AC power
- To power the display screen
Correct answer: To store electrical energy that is rapidly discharged through the patient's chest to restore normal heart rhythm
The defibrillator's main capacitor stores electrical energy that is rapidly discharged to depolarize the heart.
Long-idle capacitors need periodic charging to maintain dielectric integrity (capacitor reformation). Biomedical technicians verify energy delivery accuracy, charge time, and internal discharge function during PM.
Question 6: What safety feature prevents a patient from receiving an uncontrolled free flow of IV fluid if the tubing is removed from an infusion pump?
- The drip chamber
- Anti-free-flow clamp mechanism built into the pump door or tubing set (Correct answer)
- The roller clamp
- The filter in the tubing
Correct answer: Anti-free-flow clamp mechanism built into the pump door or tubing set
The anti-free-flow mechanism automatically occludes the tubing when removed from the pump, preventing uncontrolled fluid delivery.
A failed anti-free-flow mechanism is a critical safety failure requiring immediate removal from service. Verify during every PM by opening the door and confirming zero flow.
CBET Medical Equipment Function 2
What principle does an ultrasound imaging system use to create images of internal body structures?