Electrical Safety and Biomedical Engineering Principles Flashcards

What is the maximum allowable leakage current for patient-connected medical equipment according to AAMI/IEC standards?

Answer: 100 microamperes

AAMI/IEC 60601-1 sets 100 microamperes (0.1 mA) as the maximum allowable patient leakage current for Type B applied parts under normal conditions.

Which type of grounding system is specifically required for patient care areas in dialysis units to minimize electrical hazards?

Answer: Isolated power system

Isolated power systems (IPS) are required in critical care patient areas including dialysis to prevent ground fault currents from passing through the patient.

In the context of hemodialysis equipment, what does 'macroshock' refer to?

Answer: Current above 1 mA applied to the skin surface

Macroshock refers to currents above approximately 1 mA that are perceptible at the skin surface and can cause muscle contraction, respiratory arrest, or ventricular fibrillation at higher levels.

What is the primary purpose of a line isolation monitor (LIM) in a dialysis unit?

Answer: To detect loss of isolation in an isolated power system

A line isolation monitor continuously measures the impedance between the isolated power lines and ground, alarming when the fault hazard current exceeds safe limits (typically 2 mA or 5 mA).

Which class of medical electrical equipment relies solely on basic insulation for patient protection with NO protective earth connection?

Answer: Class II

Class II equipment (double-insulated) uses reinforced or double insulation rather than a protective earth connection to protect against electric shock.

What is the recommended frequency for electrical safety testing of patient-connected hemodialysis equipment per AAMI standards?

Answer: Every 6 months

AAMI recommends electrical safety inspection and testing of patient-connected equipment at least every 6 months or per the manufacturer's recommendations.

What is 'microshock' hazard in hemodialysis patients particularly relevant for those with central venous catheters?

Answer: Currents as low as 10–20 microamperes applied directly to the heart

Microshock involves currents as low as 10–20 microamperes that bypass skin resistance via internal pathways (e.g., central catheters) and can induce ventricular fibrillation.