Final answer:
The second assessment of a baby's heart rate should be done after approximately 60 seconds of positive pressure ventilation (PPV) that moves the chest.
Step-by-step explanation:
The second assessment of a baby's heart rate should be done after approximately 60 seconds of positive pressure ventilation (PPV) that moves the chest. PPV is a technique used to provide artificial breathing assistance to a newborn who is not breathing or is experiencing difficulty in breathing.