What is the Difference Between Grounded vs. Ungrounded Lines in an Operating Room?

How to protect patients and hospital staff from electrical hazards

In order to have a healthy appreciation of the electrical hazards in an operating room, we must assume and understand that the patient laying on the OR (operating room) table is connected to the ground and therefore a part of the electrical ground system in the operating room. This is also true for nurses and doctors. What are the implications of this assumption? Simply put, electrical currents can flow through the people in the operating room (electrocution) when insulation failure occurs. The severity and probability of electrocution depend on the type of electrical protection designed into the operating room. “Ungrounded Systems” require insulation faults at two different points and a large enough voltage difference between those two points before current will flow through the ground. As we will discuss later, “Grounded Systems” only require one fault to result in electrical current flow through the ground.

Components often found connected to “Ungrounded Systems” in operating rooms:

• Circuit Breakers in the Isolation Power Panel (IPP)
• The Line Isolation Monitor (LIM)
• Most receptacles (electrical outlets) distributed throughout the operating room
• The surgical lights
• Isolation transformer secondary winding. (Note that the transformer’s primary winding is attached to a different isolated electrical system)
• Power cords have insulated copper conductors. The purpose of the cord’s insulation is to keep the copper from touching “Ground"
• When plugged into a receptacle, the instruments used by the medical team
• Suction pumps, ventilators, Bobies - Bipolar electrocautery tools, heart and oxygen monitors