CPR 30:2 Ratio: Physiology, Evidence & Why It Works

The 30:2 compression-to-ventilation ratio (for single-rescuer adult CPR) balances perfusion and oxygenation based on resuscitation science:

1. Maximize Coronary & Cerebral Perfusion

Chest compressions generate forward blood flow. Interruptions—even for breaths—drop coronary perfusion pressure (CPP). 30 compressions build adequate CPP; 2 breaths add oxygen without excessive pause.

2. Minimize Hands-Off Time

Prior 15:2 ratio caused more frequent interruptions. 30:2 reduces pauses by 50%, improving neurologically intact survival.

3. Oxygen Reserve Utilization

At cardiac arrest, arterial oxygen content is initially adequate. Compressions circulate this reserve. Ventilation becomes critical only after ~4–5 minutes.

4. Single-Rescuer Feasibility

30 compressions (~18 sec) + 2 breaths (~4 sec) = 22-sec cycle. Sustainable for one provider; allows near-continuous compressions.

5. Guideline Consensus

Endorsed by AHA, ERC, ILCOR since 2005. Supported by animal data, mathematical modeling, and observational human studies showing improved ROSC and survival with higher compression fractions.

Exceptions

• Advanced airway in place: Continuous compressions (100–120/min) + 1 breath q6 sec (10/min).
• Pediatrics (2-rescuer): 15:2.
• Neonates: 3:1 (compressions:ventilations).

High-quality compressions (depth ≥2", rate 100–120, full recoil, minimal pauses) matter more than perfect ratio adherence.