Electrical safety in the ICU

After years of neglect, this fascinating topic has finally founds its way into the fellowship exam in the form of Question 22 from the first paper of 2016.

Microshock: small current delivered via electrodes directly into the body, bypassing the resistance of the poorly conductive skin.

Equipotential earthing

  • Ensures all equipment is earthed at the same low potential

Residual current devices (RCDs)

  • Detect current leak
  • Breaks circuit if the leak is detected

Line isolation monitors (LIMs)

  • Monitor escess current
  • Alarm when excess current detected

Uninterruptible power supply

  • Connected to battery banks or diesel generator.
  • Blue sockets for battery UPS, red sockets for generator backup

Protected areas:

  • Cardiac protected electrical area
    • Areas where microshock is likely, eg. areas where patients have intravascular devices
    • These areas have equipotential earthing and RCDs/LIMs
  • Body protected electrical area
    • Areas where microshock is unlikely (eg. outpatient clinics, anywhere there is ECG monitoring)
    • RCDs/LIMs are used

Equipment electical safety is classified by the permitted current leak:

  • Type B devices can leak all they want
  • Type BF devices can only leak a maximum of 5mA
  • Type CF devices can only leak a maximum of 50μA


O'HARA Jr, JEROME F., and THOMAS L. HIGGINS. "Total electrical power failure in a cardiothoracic intensive care unit." Critical care medicine 20.6 (1992): 840-845.


Olson, Walter H. "Electrical safety." Medical instrumentation. Boston: Houghton Mifflin Co (1978): 667-707.

Χριστοδούλου, Χριστόφορος. Recommendations and standards for building and testing an Intensive Care Unit (ICU) electrical installation. Diss. 2011. - This is a fascinating masters thesis dissertation on the standards of electrical equipment in ICU. It is not exactly a canonical source- as I expect the CICM engineers use other, locally validated guidelines -but it is an interesting read nonetheless, particularly because the author makes his recommendations on the basis of published evidence. Thus, this is the nearest thing I can find to "evidence-based ICU design".