In CPR, what signifies that ventilation has been successfully achieved?

Successful ventilation during CPR is primarily indicated by the rise of the chest. This physical sign confirms that air is being effectively introduced into the lungs, leading to adequate oxygenation of the bloodstream. When chest rise is observed, it suggests that the airway is open and that the necessary steps for effective ventilation, such as proper head-tilt-chin-lift maneuvers or the use of an airway adjunct, are being executed correctly.

The other options, while important in the broader context of patient recovery, do not directly indicate successful ventilation. For example, the patient regaining consciousness could happen due to various reasons and is not a definitive sign of proper ventilatory support. Pupil reaction to light can indicate neurological function but is not a reliable indicator of ventilation efficacy. Normalization of the heartbeat may occur as a result of effective overall resuscitation efforts but does not specifically relate to the ventilation process. Therefore, the rise of the chest is the most clear and direct observation that confirms successful delivery of breaths during CPR.