What results in passive ventilation during CPR?

Passive ventilation during CPR is primarily the result of chest recoil during chest compressions. When chest compressions are performed, they create a cycle of pressure changes in the thoracic cavity. During compression, the chest wall is pushed down, increasing intrathoracic pressure and forcing blood out of the heart. When the compressions are released, the chest recoils back to its normal position, which decreases the intrathoracic pressure.

This decrease in pressure allows air to flow back into the lungs passively, as the negative pressure draws in ambient air. This passive movement of air into the lungs is vital for providing oxygenation during CPR, especially in scenarios where artificial ventilation isn't applied. Thus, the effective recoil of the chest plays a crucial role in enabling this process, facilitating gas exchange even when the heart is not actively pumping blood.