Risk of Electric Shock from Patient Monitoring Cables and Electrode Lead Wires
Hazard [Health Devices May-Jun 1993;22(5-6):301-2]
In 1987, we published a Hazard Report on
patients who received electric shocks when they were inadvertently connected to
line power (120 VAC). These incidents occurred when electrode lead wires, which
should have been attached to the patient cables connected to ECG or home apnea
monitors, were instead plugged into energized detachable power-line-cord plugs
(see "Connection of Electrode Lead Wires to Line
Power," Health Devices 16, Feb 1987).
Since that time, we have become aware of several additional cases of
patient injury, apparently also the result of electric shock from misconnection of
electrode lead wires into line-cord plugs (120 VAC). The reported incidents have occurred
in hospitals and homes, and the misconnection has been made by clinicians (e.g., nurses)
and caretakers (e.g., parents), as well as children (usually siblings). This ongoing
problem has prompted us to update our report.
The mechanism for this hazard is
inappropriate connection of two medical device components—unprotected
patient electrode lead wires and detachable device
line cords. A typical misconnection occurs when the thin, round,
conductive male pins located at the cable end of electrode lead wires are inserted into
the slotted female connectors of an energized line cord or extension cord; these
connectors are intended to receive the plug blades of an electrical device, not the lead
Typically, misconnection is caused by confusion about the cables used in
ECG (heart electrical activity) and apnea (heart and respiratory activity) monitors. The
problem may be exacerbated by the coincident color coding (e.g., black, white, green) of
electrode lead wires and line-cord wires. Line-cord wires, whose color coding typically
matches that of the electrode lead wires, can frequently be seen through transparent
female power connectors on the detachable power cords used on many hospital devices.
Conclusions and manufacturer responses
ECRI recommends that all unprotected patient
cables and electrode lead wires be immediately removed from service; we also
recommend that manufacturers and equipment lessors supply only safe monitoring
cables and lead wires. Safe or "protected cable/lead system" connectors are
constructed in a lock-and-key configuration that conceals the electrically conductive
junctions to prevent insertion into line cords and electrical outlets.
In our evaluation of infant apnea monitoring systems (see "Infant
Home Apnea Documentation Monitors," Health Devices 21, Oct 1992), we
discovered that all apnea monitor manufacturers now provide only protected cable/lead
systems to home users; however, at least one manufacturer offers unprotected cable/lead
systems to hospitals. Most ECG monitor manufacturers still offer both protected and
unprotected cable/lead systems; however, one manufacturer has recently informed us that it
will discontinue the manufacture and sale of all unprotected systems.
Hospitals that operate equipment-leasing programs, as well as all
nonhospital-based equipment lessors, should ensure that they supply safe patient
monitoring cables and electrode lead systems.
- Immediately locate and discard all patient
monitoring cables and electrode lead wires that do not protect against
accidental connection to line cords; also, purchase electrode lead wires
with compatible patient cables and protected connectors for all ECG and
respiration/apnea monitoring systems.
- If it is not possible to immediately remove unsafe patient cables and
electrode lead wires from service, take the following precautions during the
transition period to help minimize the risk of connecting patients to line
- Warn clinical and housekeeping personnel of the
potential for patients to receive electric shocks, as described in this
- When temporarily disconnecting a patient from a
monitor, either disconnect the cable from the monitor, or disconnect the
lead wires from the electrodes. Do not disconnect the lead wires from
the patient cable.
- Hard-wire or secure (e.g., with a cable clamp)
detachable medical device line cords to the device. If this is not
practical or if the cord must be removed for transport, consider
attaching a warning label to the female connector end of the remaining
detachable line cords that states "120 VOLTS." We recommend
placing the label immediately next to the female connector, rather than
some distance up the line cord.
- Never leave a detached line cord or unused
extension cord plugged into an AC receptacle.
- Avoid use of extension cords in the vicinity of
- Store unused electrode lead wires out of the
reach of children; cut up and discard defective lead wires.
- Consider using childproof outlet caps in
pediatric departments that do not have tamperproof receptacles and in
homes with children under six years old.
- Alert home care dealers to this report; also alert parents who have
a child on a cardiorespiratory monitor at home or who have permission to
disconnect the child from or reconnect the child to a monitor in the
- Cables/Leads, ECG [15-754]
- Apnea Monitors [12-575]
- ECG Monitors [12-599]
Cause of Device-Related Incident
Device factor: Design/labeling error
User error: Improper connection
Support system failure: Use of inappropriate devices
Mechanism of Injury or
Burn (electrical); Electrical shock/electrocution