A Airway: *Establish appropriate airway management.
B Breathing: Ventilate with O2. Assess adequacy of ventilation, e.g., by exam, chest rise, SaO2 monitor, CO2 detector, esophageal detector, as indicated.
C Circulation: IV/IO. Attach monitor leads. Follow appropriate ACLS algorithm. Give rhythm-appropriate medications. Get vital signs/EKG/labs. Continue effective **CPR as indicated. Minimize chest compression interruptions to <10 seconds.
D Differential Diagnosis: Attempt to identify and treat reversible causes. See Differential Diagnosis table.

 * Okay to briefly delay advanced airway early in cardiac arrest if bag-mask ventilation is adequate in order to minimize chest compression interruptions.
** After advanced airway management is established, CPR = uninterrupted chest compressions at 100/min with 8-10 breaths/min.