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When Is an Alarm Not an Alarm?

posted Mar 6, 2018, 8:22 AM by Frank O'Brien   [ updated Mar 6, 2018, 11:48 AM ]
There’s been discussions about whether a medical equipment signal (visual, and if necessary auditory) is an actual alarm signal or just an information signal. The current work on Amendment 2 to IEC 60601-1-8, which is in the committee draft 1 (CD1) phase, seeks to better inform these discussions.

First of all, an alarm signal must signal a potential or actual exposure to harm to the patient for which operator awareness or response is required. The severity of harm and the required response time (immediate, prompt, or delayed) define alarm priorities. There are new notes to the priority definitions to clarify how they affect the clinician’s normal workflow (e.g., dressing change, line insertion).
  • A high-priority alarm condition requires an interruption of the caregiver’s current workflow.
  • A medium-priority alarm condition requires replanning of the caregiver’s current workflow.
  • A low-priority alarm condition requires planning of the caregiver’s future workflow.

Alarm systems themselves can present a hazard. Alarm priorities must be consistent with the expected interruption to workflow to avoid alarm fatigue (desentization) and alarm flooding (too many to timely manage). For example assigning a high priority, when the response time of low or medium priority would be sufficient to address the hazardous situation is generating an alarm signal for a response that’s clinically nonactionable. To avoid alarm fatigue and alarm flooding, the draft standard also includes requirements to avoid false positive and false negative alarm conditions, and nuisance alarm signals (disruptions to workflow aren’t justified by the benefit). The hope is alarm priority assignments by particular standards and manufacturers’ own risk assessments might improve to reduce the number of clinically nonactionable alarms.

Examples of information signals, which are independent of the detection of a hazardous situation include:
  • The decreasing tonal frequency of the auditory information signal of some pulse oximeters. The decreased tone is “alarming” to the operator, but in itself is not an alarm signal.
  • An electrocardiograph waveform display indicating ventricular fibrillation (“alarming” to the operator, not itself alarm signal).
  • A heart rate display of 20 beats per minute (“alarming” to the operator, not itself alarm signal).
  • Fluoroscopy beam-on indication
  • HF surgical output is energized indication
  • Non-time-critical equipment state indicators

In summary, alarms are risk controls, intended to affect a clinician’s normal workflow. Information signals are also risk controls, as they provide information for safety, but are not necessarily intended to affect a clinician’s normal workflow.

For more information on Amendment 2 to 60601-1-8 contact your national committee. In the US, the contact is Hae Choe at AAMI, hchoe@aami.org. An excellent article on alarm priorities and disruptions to work flow is “Understanding Caregiver Workflows: A Proposal for Alarm Condition Priorities”, by F. E. Block III, and F. E. Block Jr., which appeared in Biomedical Instrumentation & Technology, March/April 2016, 50(2), pp.114-116.

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