The recommended ratio of chest compressions to ventilations during cardiopulmonary resuscitation (CPR) depends on the age of the victim and the number of rescuers performing CPR.
For adult victims of cardiac arrest, the recommended ratio is 30:2. This means that rescuers should perform 30 chest compressions followed by 2 ventilations.
For pediatric victims of cardiac arrest, the recommended ratio is 15:2 for single rescuer CPR and 10:2 for two-rescuer CPR. For infants, the recommended ratio is 30:2 for both single and two-rescuer CPR.
The 3:1 ratio may be used in some special circumstances, such as in cases where advanced airway management is in place or when there are limited numbers of rescuers available. However, the 30:2 ratio is the most commonly used and recommended ratio for CPR in adults and children.