CBET Medical Equipment Function 5 — Questions and Answers
Question 1: An automated external defibrillator (AED) analyzes cardiac rhythm before delivering a shock. Which rhythm is the device specifically designed to treat?
- Ventricular fibrillation and pulseless ventricular tachycardia (Correct answer)
- Asystole and pulseless electrical activity
- Atrial fibrillation with rapid ventricular response
- Complete heart block with bradycardia
Correct answer: Ventricular fibrillation and pulseless ventricular tachycardia
AEDs are designed to detect and shock VF and pulseless VT, which are the only shockable rhythms amenable to defibrillation.
Question 2: In a capnograph, end-tidal CO2 (EtCO2) is measured at which point in the respiratory cycle?
- At the plateau of the alveolar phase, just before inhalation begins (Correct answer)
- At the beginning of exhalation when dead-space gas exits first
- At peak inhalation when alveolar gas is maximally diluted
- Midway through exhalation when flow rate is highest
Correct answer: At the plateau of the alveolar phase, just before inhalation begins
EtCO2 represents alveolar gas concentration and is read at the end-expiratory plateau, just before the next inhaled breath dilutes the sample.
Question 3: A sequential compression device (SCD) used for DVT prophylaxis works by:
- Sequentially inflating air bladders from distal to proximal to propel venous blood toward the heart (Correct answer)
- Applying continuous uniform pressure to compress deep veins at a fixed pressure
- Delivering electrical stimulation to calf muscles to induce rhythmic contractions
- Cooling the extremity to slow venous blood flow and prevent clot propagation
Correct answer: Sequentially inflating air bladders from distal to proximal to propel venous blood toward the heart
SCDs mimic the calf-muscle pump by inflating segments distally to proximally, augmenting venous return and reducing stasis.
Question 4: In an infusion pump, the 'VTBI' setting refers to:
- Volume to be infused — the total volume programmed to deliver before the pump alarms (Correct answer)
- Velocity of the titrated bolus injection
- Volumetric threshold before infusion interruption
- Vascular tone-based infusion index
Correct answer: Volume to be infused — the total volume programmed to deliver before the pump alarms
VTBI (Volume To Be Infused) tells the pump how many mL to deliver; it alarms or stops when this limit is reached to prevent over-infusion.
Question 5: A bladder scanner uses which technology to estimate post-void residual urine volume non-invasively?
- Ultrasound imaging that calculates bladder volume from 3D geometric measurements (Correct answer)
- Infrared thermography detecting bladder wall temperature changes
- Bioelectrical impedance measuring fluid resistance across the lower abdomen
- Magnetic resonance imaging of pelvic structures
Correct answer: Ultrasound imaging that calculates bladder volume from 3D geometric measurements
Portable bladder scanners use ultrasound to image the bladder and apply geometric algorithms (typically prolate ellipsoid formula) to estimate volume.
Question 6: In a phacoemulsification unit used for cataract surgery, ultrasonic energy at approximately 40 kHz is used to:
- Fragment and emulsify the lens nucleus so it can be aspirated from the eye (Correct answer)
- Weld the corneal incision closed after lens removal
- Sterilize the surgical field before lens implantation
- Measure intraocular pressure during the procedure
Correct answer: Fragment and emulsify the lens nucleus so it can be aspirated from the eye
The phaco tip vibrates at ultrasonic frequency to break up the crystalline lens into small pieces that are simultaneously aspirated through the same handpiece.
Question 7: A transcutaneous electrical nerve stimulation (TENS) unit provides pain relief primarily through which mechanism?
- Activation of large-diameter sensory fibers that inhibit pain signal transmission via gate control theory (Correct answer)
- Direct destruction of nociceptors in the skin to permanently reduce pain sensitivity
- Electrical stimulation of motor neurons causing muscle contractions that release endorphins only
- Induction of local anesthesia by depolarizing small C-fiber pain neurons simultaneously
Correct answer: Activation of large-diameter sensory fibers that inhibit pain signal transmission via gate control theory
TENS stimulates Aβ fibers whose signals converge in the dorsal horn and inhibit pain transmission from smaller Aδ and C fibers, per the gate control theory.
CBET Medical Equipment Function 5
An automated external defibrillator (AED) analyzes cardiac rhythm before delivering a shock.
Which rhythm is the device specifically designed to treat?