Final answer:
The heart rate after 15 seconds of PPV cannot be determined based on the provided information.
Step-by-step explanation:
Based on the provided information, the heart rate after 15 seconds of PPV (positive pressure ventilation) cannot be determined. The correlation between heart rates and cardiac output states that as heart rate continues to increase, stroke volume (SV) gradually decreases due to decreased filling time, which eventually affects cardiac output. However, without knowing the specific circumstances, it is not possible to determine the heart rate after 15 seconds of PPV.