Paramedics have been given instructions on how to deal with potential faults, however, the procedure can take up to 5 minutes to complete.
Concerns have been raised by some ambulance workers after a piece of life-saving equipment failed during a recent emergency call-out.
A number of the cardiac devices been removed from service following an error message during call out in south Leinster.
Paramedics have since been given instructions on how to deal with potential faults, however, the procedure can take up to 5 minutes to complete.