Final answer:
During CPR, compressions are done using the heels of the hands positioned on the sternum between the T4 and T9 vertebrae to effectively circulate blood and prevent brain damage.
Step-by-step explanation:
Stern compressions during CPR are made with the heels of the hands placed on the sternum between the lines at T4 and T9. This specific hand positioning is crucial as it allows for effective compression of the heart, forcing blood into the pulmonary and systemic circuits, which is vital for brain health due to the risk of neuron death from lack of blood flow. It is important to be trained properly in CPR techniques, as improper hand placement can cause severe injuries to the patient, such as broken ribs or damage to the liver if the hands are placed too low on the sternum.