What is the primary method used to restore a normal heart rhythm in an individual experiencing cardiac arrest?

Defibrillation is the primary method used to restore a normal heart rhythm in an individual experiencing cardiac arrest because it delivers a dose of electric shock to the heart, re-establishing an effective rhythm. During cardiac arrest, the heart may be in a chaotic rhythm such as ventricular fibrillation or pulseless ventricular tachycardia, and defibrillation aims to reset the heart's electrical activity, allowing it to regain a coordinated and effective pumping action.

While CPR is vital in maintaining blood flow to vital organs until defibrillation can be administered, its primary purpose is not to restore heart rhythm but to provide manual circulation. Medications can support treatment during cardiac arrest but are often administered subsequently and do not immediately correct the arrhythmia. Oxygen therapy, while important for overall patient care, does not directly impact the heart rhythm during an arrest event. Therefore, defibrillation stands out as the most immediate and effective intervention in restoring normal heart rhythm during cardiac arrest situations.