Final answer:
The carotid pulse is the most commonly used pulse to assess the efficacy of CPR during a cardiac arrest.
Step-by-step explanation:
When responding to a cardiac arrest, it may be difficult to palpate the pulse due to the crowded area near the patient's head. However, the carotid pulse is the most commonly used pulse to assess the efficacy of CPR. This pulse is located in the neck and is easily accessible. By palpating the carotid pulse during CPR, you can determine if the compressions are effectively circulating blood.