Reducing the Risk of Power Loss to Critical Equipment
Hazard [Health Devices Apr-May 1998;27(4-5):172-4]
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
- 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
- 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.
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.
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.
- 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
Units should adequately alarm when power is lost.
Units' power indicators should have the following
- 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.
The following information should be available with
units that use battery power for primary or backup operation:
- 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.
Ideally, an alternate power source should be readily available for any
- 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.
- 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
- Certain very critical devices that can only be battery powered
should have a spare, fully charged battery stored in or with the
Device factors: Design/labeling error;
User errors: Failure to perform pre-use inspection; Incorrect clinical use
External factor: Power
Support system failures: Lack or failure of
incoming and pre-use inspections; Poor prepurchase
Mechanism of Injury or
Failure to deliver therapy; Monitoring