Cause of Device-Related Incident
Device factors; Support system failures

Clinical Specialty or Hospital Department
CCU / ICU / NICU; Clinical/Biomedical Engineering; Facilities Engineering; Nursing; Obstetrics and Gynecology

Device Factors
Improper modification

Document Type
User Experience Network (UEN) reports

External Factors
*Not stated

Mechanism of Injury or Death
Monitoring failure

Support System Failures
Poor prepurchase evaluation

Tampering and/or Sabotage
*Not stated

User Errors
*Not stated

Nurse Call Systems [15-614]; Physiologic Monitoring Systems, Acute Care [12-647]

Nurse-Call Systems Interfaced to Bedside Patient Monitors

User Experience Network™ [Health Devices Mar-Apr 1992;21(3-4):138-9]


Our physiologic patient monitoring system is interfaced to a central station monitor that has an arrhythmia computer. We have also interfaced our nurse-call system to the alarm-out jack on each of the bedside monitors to provide redundant audible alarms at the nurses station, as well as a visual indicator above the door of the patient's room. However, because heart-rate alarms will not activate the alarm-out relay, heart-rate alarms are not annunciated by the nurse-call system.


Several problems and risks are associated with simultaneously using a nurse-call system for alarm notification, as well as for its intended function:

  • Distinguishing a nurse call from an alarm. When the nurse-call system activates, the nurse has no way of knowing whether a patient is pressing the nurse-call button or the monitor is alarming (e.g., whether the patient has to go to the bathroom or has a high heart rate). If nurses learn to rely on the nurse-call system for alarm information, they may not respond as quickly to alarms on those patients who overuse the nurse-call button.
  • Lack of alarm prioritization. The light above the patient's door and the tone at the nurses station are the same, regardless of the alarm priority (e.g., ventricular fibrillation or a couplet), whereas most central station monitoring systems have prioritized alarm tones.
  • Failure to trigger the nurse-call system. Many of the patient monitoring systems that have an external alarm output or an alarm relay output either have limits on the types of alarms that will activate them or allow the alarms to be custom configured. In both instances, it will not be obvious to the nurses which bedside monitor alarms are on the nurse-call system and which are not. In the reported case, the heart-rate alarms would not activate the nurse-call system, and some of the hospital staff members were unaware of this serious system limitation. In addition, several hospitals that have purchased custom-designed monitor/nurse-call system interfaces have experienced very unreliable results.


We recommend that a nurse-call system be used solely to signal nurses that a patient needs assistance. Patient monitors already have remote-alarm capabilities through the central station monitoring system. If the layout of the patient care unit is such that nurses cannot hear the central station alarms in all locations or if a device that has critical alarms is used without a central station monitoring system, then a better means of providing remote-alarm capabilities should be investigated. For example, some vendors offer remote-alarm panels, light panels, message panels, slave scopes, pagers, and bed-to-bed communication.

If an indicator light is needed outside each room, hospitals may want to install a different light above the door in addition to the nurse-call light. (Some nurse-call systems have multiple indicator lights above each door with one light dedicated to an alarm output.) Although this solution avoids the confusion between patient requests and alarms, it does not eliminate the need to check the monitor either in the room or at the central station to assess the severity of the alarm. It is also necessary to verify that all appropriate alarms will activate the monitor's alarm output and to ensure that this function is not modified by users. Also see our Guidance Article "Update: Critical and Remote Alarms," Health Devices 18(12), Dec 1989, in which we discussed the importance of understanding the limitations of remote-alarm systems that do not alarm for equipment that is either disconnected or turned off.


  • Nurse Call Systems [15-614]
  • Physiologic Monitoring Systems, Acute Care [12-647]

Cause of Device-Related Incident

Device factor: Improper modification

Support system failure: Poor prepurchase evaluation

Mechanism of Injury or Death

Monitoring failure

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