ACLS ProMed Practice Test

During CPR, how you ventilate matters because each rapid breath increases intrathoracic pressure and reduces the amount of blood returning to the heart. This drop in venous return lowers preload and, more importantly, decreases coronary perfusion pressure—the pressure driving blood to the heart muscle between compressions. When coronary perfusion pressure falls, the chance of returning to a sustainable heartbeat (ROSC) goes down. That’s why minimizing hyperventilation is important: you want enough ventilation to oxygenate without pushing in air so forcefully or so rapidly that it impedes blood flow to the heart and brain. Hyperventilation can also cause hypocapnia and cerebral vasoconstriction, further reducing brain perfusion. The other statements aren’t correct because overly rapid ventilation doesn’t improve perfusion or ROSC, and it doesn’t inherently boost defibrillation success.