In adult single-rescuer CPR, what is the recommended number of chest compressions per cycle before ventilation?

• A. 20 compressions per cycle
• B. 40 compressions per cycle
• C. 30 compressions per cycle
• D. 60 compressions per cycle

Answer: (C)

In adult single-rescuer CPR the cycle is built around maximizing blood flow while still providing oxygen. The recommended pattern is 30 chest compressions followed by 2 rescue breaths, and then you resume compressions. This 30-compression block is chosen because it delivers a strong, continuous flow of blood to the heart and brain, which is crucial for survival, and it keeps interruptions to a minimum. If you compress too few times before giving breaths, perfusion drops; if you push for longer before ventilating, you waste time pausing compressions and still disrupt flow. The cadence also fits a practical rhythm: at about 100–120 compressions per minute, 30 compressions take roughly 15 seconds, with 2 quick breaths taking a couple more seconds, then you’re back to chest compressions without extended interruptions. This balance helps maintain perfusion pressure while providing essential oxygenation, and it’s the standard approach for adults when a single rescuer is performing CPR. If you’re unable to provide ventilations, you can switch to compression-only CPR, but when ventilations are possible, 30 compressions before 2 breaths is the recommended cycle.