Why may excessive ventilation during CPR be harmful?

Why may excessive ventilation during CPR be harmful?

• A. It reduces intrathoracic pressure
• B. It improves chest recoil
• C. It increases intrathoracic pressure
• D. It decreases oxygen delivery

Answer: (C)

During CPR the heart relies on chest recoil and negative intrathoracic pressure to draw blood back to the heart. When ventilation is excessive, each breath raises intrathoracic pressure rather than allowing the chest to recoil fully. That higher pressure makes it harder for venous blood to return to the right heart, reducing preload, lowering cardiac output, and thus decreasing perfusion to the brain and heart. Even if more oxygen enters the lungs, tissue oxygen delivery can worsen because perfusion drops. So the main harm is the increase in intrathoracic pressure that impairs venous return and overall circulation during CPR. Reducing intrathoracic pressure would improve venous return rather than harm it, and the issue is not primarily about improving chest recoil or decreasing oxygen delivery alone, but about the hemodynamic consequence of high intrathoracic pressure from too-ventilatory breaths.

During CPR the heart relies on chest recoil and negative intrathoracic pressure to draw blood back to the heart. When ventilation is excessive, each breath raises intrathoracic pressure rather than allowing the chest to recoil fully. That higher pressure makes it harder for venous blood to return to the right heart, reducing preload, lowering cardiac output, and thus decreasing perfusion to the brain and heart. Even if more oxygen enters the lungs, tissue oxygen delivery can worsen because perfusion drops.

So the main harm is the increase in intrathoracic pressure that impairs venous return and overall circulation during CPR.

Reducing intrathoracic pressure would improve venous return rather than harm it, and the issue is not primarily about improving chest recoil or decreasing oxygen delivery alone, but about the hemodynamic consequence of high intrathoracic pressure from too-ventilatory breaths.