What is the correct chest compression to ventilation ratio for a single rescuer performing CPR on an adult?

• A. 15 compressions to 2 breaths
• B. 30 compressions to 2 breaths
• C. 30 compressions to 3 breaths
• D. 20 compressions to 2 breaths

Answer: (C)

The main idea being tested is the standard rhythm of chest compressions and breaths for an adult with one rescuer. High‑quality compressions are the priority to keep blood flowing, and breaths are added without causing long pauses.

For an adult when you’re the only rescuer, you should do cycles of 30 chest compressions followed by 2 breaths. Keep the compressions at a rate about 100–120 per minute and a depth around 2 inches (5 cm), allowing the chest to fully recoil between compressions. After you complete 30 compressions, give two quick breaths, each about one second, and then resume compressions promptly.

This 30:2 pattern minimizes interruptions to blood flow while providing just enough ventilation to supply oxygen and remove carbon dioxide. Giving more breaths would pause compressions longer and reduce blood flow; giving fewer breaths wouldn’t oxygenate as effectively. If another rescuer becomes available, the same ratio can be maintained, and you can switch roles to reduce fatigue.