In the scenario presented, the neonate has central cyanosis and a heart rate that has increased to 70 beats per minute after 30 seconds of resuscitation. This information indicates a positive response to resuscitative efforts since an increase in heart rate is a sign of improving cardiovascular function.
At a heart rate of 70 beats per minute, the next step in management should focus on ensuring adequate ventilation. If the heart rate is less than 60 beats per minute, chest compressions would continue, but since the heart rate in this instance has risen above that threshold, stopping chest compressions is appropriate. Continuing ventilation is crucial to ensure that the neonate receives enough oxygen, which is vital given the initial presentation of central cyanosis.
The other options are not the immediate priorities in this situation. Administering epinephrine would only be indicated if the heart rate remained under 60 beats per minute despite adequate ventilation. Similarly, while volume expansion may be important in certain cases of shock, the focus in this immediate context is on ventilation due to the positive change in heart rate. Thus, the correct course of action is to stop chest compressions and continue providing ventilation to support the neonate's respiratory needs.