Cause of Device-Related Incident
Device factors; External factors; Support system failures; User errors

Clinical Specialty or Hospital Department
CCU / ICU / NICU; Clinical/Biomedical Engineering; Continuing Care; Emergency Medicine; Nursing; OR / Surgery

Device Factors
Design / labeling error; Device failure

Document Type
Hazard Reports

External Factors
Power supply (including piped medical gases)

Mechanism of Injury or Death
Failure to deliver therapy; Monitoring failure

Support System Failures
Lack or failure of incoming and pre-use inspections; Poor prepurchase evaluation

Tampering and/or Sabotage
*Not stated

User Errors
Failure to perform pre-use inspection; Incorrect clinical use

Reducing the Risk of Power Loss to Critical Equipment



Hazard [Health Devices Apr-May 1998;27(4-5):172-4]

Problem

ECRI regularly receives reports of power failures in life-support or emergency care equipment because units were not plugged in or their power cords became disconnected. Here are only a few examples:

  • A member hospital reported that a defibrillator would not operate because its detachable power cord had been inadvertently disconnected from the unit, and battery backup had been depleted without the unit alarming.
  • Another hospital reported that a detachable power cord was pulled out of an infusion pump by a patient, and the backup battery was depleted without the unit alarming.
  • A third member hospital forgot to replug a defibrillator into line power after a routine inspection; this allowed the defibrillator's battery to deplete without either an alarm or an indicator.

Power loss to a critical device can pose a risk of death or injury to patients. Even though this problem is well recognized, incidents continue to occur.

Discussion

Units can be deprived of line power in several ways. The most obvious way is disconnection of the power cord from the wall receptacle, either because the user forgot to plug it in or because the plug accidentally came loose. On units with detachable power cords (i.e., those that can be removed from the unit), the unit can likewise be deprived of line power if the cord is not adequately connected to the unit. Detachable cords are susceptible to accidental disconnection from the unit if they are not secured by a cord capture device (such as a retention clip), a cleat, or a channel. Also, users may fail to attach the cord correctly even with capture devices in place or may forget to plug the cord into the unit. This prevents power from reaching not only the unit but also its rechargeable battery backup, if there is one.

Unfortunately, a number of devices do not adequately alert the user to a power loss. For example, some units signal a disconnection using only an illuminated indicator, which can be missed. And some units do not signal when battery power is low or batteries are charging. As outlined in our Recommendations below, users should take steps to identify those critical devices that are susceptible to power cord disconnection and battery depletion without alarming, and should ensure that these devices receive particular vigilance. They should also ensure that devices purchased in the future will adequately indicate power problems.

Recommendations

General recommendations:
  • Instruct staff members who use critical devices to routinely check that power cords are attached to both the device and the electrical outlet and that the devices have power. Also instruct them to regularly check power indicators and battery charge capacity indicators, particularly on units not equipped with power-loss alarms or indicators.
  • Use the criteria described in the remaining recommendations when examining critical devices for adequate power-loss protection and when planning purchases of such equipment. Keep in mind that some criteria may not be applicable to certain devices, and few devices will meet all the criteria. The relative importance of the criteria may depend on the individual needs of the institution.
Equipment having detachable power cords should also have adequate capture devices, cleats, or channels to hold the cord in place. If these are absent, request that the devices' suppliers provide suitable means of securing the cords.

Units should adequately alarm when power is lost. Specifically:

  • Units should alert clinicians to a power failure with an audible (or, preferably, audible and visual) power-loss alarm. Ideally, this alarm should be powered by a different source (e.g., separate battery, pneumatic pressure) than the one that powers the device.
  • Units that are battery powered or that have battery backup should have audible and visual low-battery alarms to alert the operator that the power source is depleted and the unit is about to shut off. These alarms should provide enough warning that operators have time to exchange the battery for one that is fully charged or to connect the device to line power.
Units' power indicators should have the following characteristics:
  • Units should indicate which power source they are operating from. For devices operated primarily from line power, an audible alarm and visual indicator should activate to signal a changeover to battery power. The audible alarm should sound until manually reset. To conserve remaining battery capacity, this tone can be intermittent.
  • Units that are equipped with rechargeable batteries should visually indicate when the batteries are charging.
  • Battery-powered units with a visual battery charge capacity indicator (similar to a fuel gauge) are preferred. At minimum, a device should have a user-activated battery test function. Battery voltage indicators are not sufficient.
The following information should be available with units that use battery power for primary or backup operation:
  • Preferably, units should be clearly labeled to indicate the number and type of batteries inside the device. This is especially important for devices with separate alarm circuit batteries not located near the operating batteries.
  • At minimum, information on the number and type of batteries should appear in both the operator's manual and the service manual. In addition, service manuals should clearly indicate recommended battery maintenance procedures and intervals, as well as battery replacement intervals. They should also clearly indicate how to remove and replace the batteries and, if appropriate, provide instruction on avoiding the loss of data and system settings from memory while doing so.
Ideally, an alternate power source should be readily available for any unit. Specifically:
  • Units that operate from both line and battery power are preferred. These units should have the following features: a.) If line power is lost, the device should automatically switch to battery power to prevent device failure or data corruption. b.) If battery power is lost or low, the unit should be able to be plugged into line power to provide uninterrupted device operation without data corruption. c.) Battery charging should be automatic while the device receives line power and should occur even if the device is off. d.) The unit should be able to operate on line power even if the battery is depleted, short-circuited, or missing.
  • Certain very critical devices that can only be battery powered should have a spare, fully charged battery stored in or with the unit.

Cause of Device-Related Incident

Device factors: Design/labeling error; Device failure

User errors: Failure to perform pre-use inspection; Incorrect clinical use

External factor: Power supply

Support system failures: Lack or failure of incoming and pre-use inspections; Poor prepurchase evaluation

Mechanism of Injury or Death

Failure to deliver therapy; Monitoring failure


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