What is the correct approach if chest rise is not observed after ventilations?

When ventilations are provided during CPR and chest rise is not observed, the appropriate response is to reposition the head and attempt ventilation again. This is crucial because an inadequate seal around the airway or an obstructed airway can prevent effective ventilation. By adjusting the head position, typically with the chin lift or head tilt-chin lift maneuvers, you can help to open the airway more effectively, which may allow the breaths to enter the lungs properly and therefore produce visible chest rise.

Discontinuing ventilations without attempting to address the potential obstruction or improper positioning would not be advisable, as it fails to address the underlying issue that might be causing the lack of chest rise. Choosing to switch to back blows or perform the Heimlich maneuver would be inappropriate in this scenario, as those techniques are not designed for this situation where the focus should be on establishing proper ventilation rather than addressing choking or airway obstruction in a different context. Thus, repositioning the head is the most logical and effective first step when chest rise is not observed after initial attempts at ventilation.