Final answer:
In a one-person CPR scenario for a child, the standard ratio of compressions to ventilations is 30:2. Sufficient ventilation is important for oxygenation, but chest compressions should not be interrupted if ventilations cannot be effectively given.
Step-by-step explanation:
The ratio of compressions to ventilations in a child for one rescuer is 30 compressions to 2 ventilations. This is the recommended procedure in a pediatric basic life support scenario. It's important to note that while giving these ventilations, one needs to ensure that each breath lasts about one second and makes the chest rise, which indicates sufficient air has been provided. However, if the rescuer is not confident or trained in providing ventilations, they should perform continuous chest compressions at a rate of 100-120 compressions per minute until professional help arrives or an automated external defibrillator (AED) is ready for use.