What is the first step to perform CPR on an adult?

The first step to perform CPR on an adult involves calling for emergency help. This action is crucial because it ensures that professional medical assistance is on its way while you provide care. By alerting emergency services, you are initiating a vital response that can significantly improve the chances of survival for the person in distress.

Once you've called for help, you can then proceed with assessing the situation, checking the person's responsiveness, and if necessary, starting CPR. This initial step of calling for help underscores the importance of ensuring that additional resources are mobilized quickly, which is essential in emergency situations.

The other options represent important actions in the CPR process, but they should follow the call for emergency assistance. Starting rescue breathing, performing chest compressions, or checking for a pulse without first alerting emergency services can delay critical help that the victim may need. Thus, alerting emergency personnel is prioritized to create a coordinated response to the emergency.