What action should you take if a choking child suddenly becomes unresponsive?

When a choking child becomes unresponsive, the appropriate response is to start CPR and check the mouth for any visible obstruction. This is critical because unresponsiveness indicates that the child cannot breathe or may have lost consciousness due to the lack of oxygen caused by the obstruction.

In this situation, initiating CPR serves two essential purposes: it provides chest compressions to circulate blood and oxygen throughout the body, helping to keep the heart and brain functioning, and it includes rescue breaths, which help to restore oxygen levels. Checking the mouth during CPR is vital because you may be able to see and remove the object causing the choking, which could potentially save the child's life.

Other choices, such as giving back blows or performing abdominal thrusts, are appropriate actions when a child is responsive and still able to cough or breathe. However, when the child is unresponsive, those methods are no longer suitable since assisting in a conscious manner is not possible. Coughing it out is also not viable at this stage since the child cannot respond at all. Therefore, the immediate initiation of CPR is the most effective and necessary response when dealing with an unresponsive child who has been choking.