A systematic approach to diagnosing patients with suspected cardiac arrest is necessary to guide rescuers in providing optimal care. Best practice divides this into four assessments: (1) the initial impression, (2) the BLS assessment, (3) the primary assessment, and (4) the secondary assessment. 

In the initial impression, community or trained responders start by ensuring that the scene of a suspected cardiac arrest is safe for the patient and rescuers involved. 

The responder should note whether the patient is conscious or unconscious. If a patient is unconscious, the BLS assessment should be initiated. When the patient is conscious, the responder should remain with them and call 911.

Related Video: Understanding the Systematic Approach Algorithm

A community member performing CPR on a patient in public.