In which situation is it appropriate to perform chest compressions only in CPR?

Performing chest compressions only during CPR is most appropriately indicated in situations of witnessed sudden cardiac arrest in adults. In such cases, it is often assumed that the cardiac arrest is due to a primary cardiac issue, and since the emphasis is on immediately restoring circulation, chest compressions become the priority action to help maintain blood flow to vital organs until advanced care arrives.

In situations where there are other contributing factors, such as drowning incidents or children with breathing difficulties, it's essential to address the underlying cause of the arrest, which often includes providing rescue breaths alongside chest compressions. Drowning victims usually require both ventilatory support and chest compressions due to asphyxia, while children experiencing breathing difficulties may even benefit from immediate rescue breaths due to their higher susceptibility to respiratory complications. Fainting generally does not require CPR unless the person does not recover and becomes unresponsive, at which point the situation would also likely lean towards the need for rescue breaths.

Thus, witnessed adult cardiac arrests form the specific context where high-quality chest compressions alone are sufficient and recommended until further medical assistance is available.