CABT Healthcare and Electrical Safety Questions and Answers — Questions and Answers
Question 1: A nurse reports feeling a slight tingling sensation when simultaneously touching a patient's metal bed frame and the chassis of a portable ECG machine. This situation most likely indicates which electrical safety issue?
- A faulty power switch on the ECG machine.
- Excessive chassis leakage current. (Correct answer)
- Normal static electricity discharge.
- An overloaded power circuit.
Correct answer: Excessive chassis leakage current.
A tingling sensation occurs when a small amount of current flows through the body. This is a classic sign of excessive leakage current from the medical device's chassis. If the ground path is compromised or the leakage is above safe limits, a person touching the device and a grounded object (like the bed frame) can complete a circuit, experiencing a shock.
Question 2: According to the NFPA 99 standard, what is the maximum allowable ground wire resistance for a piece of cord-connected medical equipment used in a patient care setting?
- 5.0 Ohms
- 0.1 Ohms
- 1.0 Ohm
- 0.5 Ohms (Correct answer)
Correct answer: 0.5 Ohms
NFPA 99 and AAMI standards specify that the resistance of the protective earth ground wire in cord-connected medical equipment must be very low to ensure safety. A low-resistance path allows fault current to flow to the ground and trip a circuit breaker, rather than passing through a patient or staff. The widely accepted maximum limit is 0.5 Ohms.
Question 3: Which of the following is the most significant danger associated with microshock?
- Severe skin burns at the point of contact.
- Induction of ventricular fibrillation from a very low current. (Correct answer)
- Involuntary muscle contraction causing patient injury.
- Overheating of internal electronic components.
Correct answer: Induction of ventricular fibrillation from a very low current.
Microshock is hazardous because it involves a very small current applied directly to or near the heart, bypassing the skin's high resistance. Currents as low as 10 to 20 microamperes can be sufficient to induce ventricular fibrillation, a life-threatening cardiac arrhythmia. Macroshock, in contrast, involves larger currents passing through the skin.
Question 4: A biomedical technician is replacing a wall outlet in a patient's room designated as a "wet procedure location." Which type of receptacle is required to be installed to enhance safety?
- A standard residential-grade duplex receptacle.
- An industrial-grade, twist-lock receptacle.
- A hospital-grade receptacle. (Correct answer)
- A surge-protecting receptacle.
Correct answer: A hospital-grade receptacle.
Hospital-grade receptacles are mandatory in patient care areas, especially wet locations. They are built to higher standards of durability and, most importantly, provide superior and more reliable grounding contact retention to withstand frequent use and abuse, which is critical for patient safety. They are identifiable by a green dot on the face of the receptacle.
Question 5: What is the primary safety function of an isolation transformer in the power supply of medical equipment used in an operating room?
- To increase the line voltage for high-power devices.
- To convert the incoming AC power to DC power.
- To create an ungrounded secondary circuit, reducing macroshock risk. (Correct answer)
- To act as the primary circuit breaker for the device.
Correct answer: To create an ungrounded secondary circuit, reducing macroshock risk.
An isolation transformer's primary purpose in medical systems is safety. It creates a secondary power source that is electrically isolated from the grounded primary. This means that a person touching one live conductor and ground will not complete a circuit, drastically reducing the risk of a dangerous macroshock, which is especially important in critical care areas like operating rooms.
Question 6: During an electrical safety inspection, a technician tests a portable patient monitor. Under NFPA 99 guidelines for equipment used in the patient care vicinity, the chassis leakage current must NOT exceed:
- 10 milliamperes
- 500 microamperes
- 300 microamperes (Correct answer)
- 100 microamperes
Correct answer: 300 microamperes
NFPA 99 sets specific limits for leakage current to ensure patient safety. For portable cord-connected appliances used within the "Patient Care Vicinity," the chassis leakage current must not exceed 300 microamperes (µA). This limit helps prevent microshock and macroshock hazards.
CABT Healthcare and Electrical Safety Questions and Answers
A nurse reports feeling a slight tingling sensation when simultaneously touching a patient's metal bed frame and the chassis of a portable ECG machine.
This situation most likely indicates which electrical safety issue?