Electrical Safety and Biomedical Engineering Principles Flashcards

What is the primary purpose of equipotential bonding in a hemodialysis patient care area?

Answer: To ensure all conductive surfaces are at the same electrical potential, eliminating current flow between them

Equipotential bonding connects all exposed conductive parts to a reference point so no voltage difference exists between them, preventing current from flowing through a patient who touches two surfaces.

A biomedical technician measures 150 microamperes of chassis leakage current on a hemodialysis machine. What is the appropriate action?

Answer: Remove the machine from service immediately and tag it out of service

A chassis leakage current of 150 µA exceeds the AAMI limit of 100 µA, requiring the machine to be removed from service until the fault is identified and corrected.

In biomedical engineering terms, what does 'applied part' mean in the context of IEC 60601-1 for dialysis equipment?

Answer: The part of equipment that comes into physiological contact with the patient

Per IEC 60601-1, an 'applied part' is any part of medical electrical equipment that in normal use necessarily comes into physical contact with the patient for the equipment to perform its function.

Which protection classification under IEC 60601-1 designates equipment with a floating (isolated) patient connection suitable for cardiac applications?

Answer: Type CF

Type CF ('C' = cardiac, 'F' = floating/isolated) applied parts have the most stringent leakage current limits (10 µA) and isolated patient connections, making them suitable for direct cardiac contact.

What is the correct method for testing ground wire integrity on hemodialysis equipment using a biomedical safety analyzer?

Answer: Pass at least 25 amperes DC through the ground conductor and measure resistance

AAMI/ANSI standards require ground wire testing with a high-current source (typically 25 A) to stress the ground conductor and accurately measure resistance, as low-current ohmmeters cannot detect poor connections under load.

During a power failure in a dialysis unit, which component of the electrical system is designed to provide immediate backup power to hemodialysis machines without interruption?

Answer: Uninterruptible power supply (UPS)

A UPS (uninterruptible power supply) provides instantaneous battery-backed power during outages, while generators have a transfer delay of several seconds that could interrupt treatment.

According to AAMI TIR No. 12, what is the recommended maximum resistance for the protective earth (ground) conductor in patient-connected medical equipment?

Answer: 0.1 ohm

AAMI TIR No. 12 and IEC 60601-1 specify that protective earth resistance must not exceed 0.1 ohm to ensure a reliable low-impedance fault return path that will trip protective overcurrent devices.