The use of a defibrillator can greatly increase the chance of patient survival if they require resuscitation.
Defibrillators are portable devices able to recognise shockable versus non-shockable rhythms in a patient in cardiac arrest and, if shockable, deliver an electric shock in an attempt to return the heart to a normal rhythm. Early access to defibrillation, when combined with early effective CPR, provides the best chance of survival for a patient suffering cardiac arrest.
In the case of patients who have been submerged in water, a defibrillator is unlikely to advise that a shock is required. This is because most drowning patients are unconscious due to respiratory failure that progresses to a non-shockable cardiac arrest rhythm. A defibrillator will recommend a shock in only a small percentage of drowning patients who may have become submerged because of another reason, such as a heart attack. It is therefore important that all lifesavers maintain their training to perform effective CPR.