When is mouth-to-mouth rescue breathing indicated in a BLS situation?

Mouth-to-mouth rescue breathing is indicated in a BLS situation, particularly when a barrier device is not available. This method is a way to provide necessary oxygen to a victim who is not breathing or not breathing effectively. While barrier devices, such as pocket masks, are preferred due to their ability to minimize the risk of disease transmission, rescuer safety is paramount. If no barrier device is available, using mouth-to-mouth ventilation allows the rescuer to perform lifesaving actions, as those breaths can still provide oxygen to the lungs of the victim and is better than providing no assistance at all.

The presence of an AED does not negate the need for rescue breaths; it can be used in conjunction with rescue breathing if indicated. Ineffective chest compressions suggest the need for ventilation, but the availability of a barrier device is what determines the method used. The victim's age, whether an adult or child, doesn’t change the necessity for mouth-to-mouth as a response to unavailability of a protective device. Therefore, the option specifying the absence of a barrier device is the most relevant for when mouth-to-mouth may be used.