IOM Instrumentation Layout and Electrical Interference

  • Brett NethertonEmail author
  • Andrew Goldstein


IOM recording technology is founded on basic electrical principles including susceptibility to electrical interference, which in the operating room is predominantly due to electromagnetic coupling of noise sources with recording circuits. The underlying physics involved will be discussed in this chapter. Methods of improving physiologic signal acquisition and reducing electrical interference will be discussed.


Basic electrical circuits Electrical interference Recording technology Impedance Electrodes Signal-to-noise ratio Grounding Signal averaging Electromagnetic fields Electrode burns 

Supplementary material

Video 16.1

The capacitance of skin

Patient skin acts as an antenna for ambient electrical interference

The location where electrical interference couples with the patient’s skin has an impact on how the interference is amplified. The skin of OR staff, for example the surgeon, can aid in coupling electrical interference to our patient

Mechanical movements of our recording electrodes and leadwires can introduce motion artifact into our signals (AVI 201856 kb)

Video 16.2

Capacitive and inductive coupling

Electrical interference readily couples with our recording leadwires, whether inductively or capacitively coupled (AVI 166585 kb)

Video 16.3

Importance of bundling leadwires

Keeping leadwires close to each other decreases the amount of electrical interference amplified by increasing the extent to which the electrical interference is common to both leadwires

Twisted or braided leadwires perform better than ribbon leadwires, which in turn perform better than loose leadwires (AVI 51689 kb)

Video 16.4

Electrical interference fields of fluid warmer and surgical headlamp

Both the fluid warmer and the surgical headlamp have directional electromagnetic fields

Creating distance rotationally, horizontally, and vertically can selectively decrease the extent of coupling to our recording circuitry (AVI 238423 kb)

Video 16.5

Electrical interference field of patient air warmer (AVI 95808 kb)

Video 16.6

OR bed wall grounded and ungrounded demonstration

Poor grounding of the OR table or other OR equipment can be a source of electromagnetic interference to our recording circuit

Unplugging the OR table may decrease the amount of electromagnetic interference coupled to our recording circuit.

It is possible that in the case where the ground of the OR table is helping to compensate for other noise sources, unplugging the OR table may increase the amount of electromagnetic interference

The iso-ground is by definition isolated from the IOM equipment main ground. The condition of the ground of the IOM equipment is therefore usually not a source of interference. It is however a safety factor (AVI 191699 kb)

Video 16.7

Importance of location of iso-ground placement on the patient

The efficacy of the iso-ground electrode to decrease electromagnetic interference is highly dependent on placement location (AVI 160414 kb)

Video 16.8

Dangers of electrode burns from coupled energy from the ESU

The electromagnetic field emanating from the ESU cabling can couple with our recording electrode leadwires, resulting in electrode burns at the electrode patient attachment

Contact between the patient’s skin and both ESU and IOM electrode cabling enhances the level of coupling occurring between the ESU cabling and IOM electrode cabling

Like other electromagnetic fields, creating distance between the source (ESU cabling) and our recording leadwires decreases the amount of coupling (AVI 289000 kb)


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Copyright information

© Springer International Publishing AG 2017

Authors and Affiliations

  1. 1.Signal Gear LLCProsperityUSA
  2. 2.Manager Biomedical Services, IONM, SpecialtyCareBrentwoodUSA

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