Final answer:
An EMT may use a defibrillator when a patient suffers sudden cardiac arrest. CPR is performed first, and if it doesn't work, a defibrillator can be used to restore normal heart rhythm.
Step-by-step explanation:
An EMT may use a defibrillator when the individual suffers a sudden cardiac arrest. This is because a defibrillator can deliver an electric shock to restore the heart's normal rhythm. CPR is usually performed before the use of a defibrillator, but if CPR does not seem to be working, the EMT may choose to use a defibrillator. The patient's history of arrhythmia is not the only prompt for using a defibrillator as sudden cardiac arrest can occur in individuals without a known history of arrhythmia.
Learn more about prompt for using a defibrillator