Which of the following occurs during positive-pressure ventilation?

During positive-pressure ventilation, intrathoracic pressure increases. This technique involves forcing air into the lungs, typically using a bag-valve-mask or mechanical ventilator. As air is pushed into the airways, it leads to an accumulation of air within the thoracic cavity. This influx of air creates higher pressure inside the thorax compared to the atmospheric pressure outside the body.

The increase in intrathoracic pressure can affect venous return to the heart; however, the primary focus with positive-pressure ventilation is understanding how it assists in delivering oxygen to the lungs by artificially increasing the pressure within the thoracic cavity. This contrasts with the mechanics of normal breathing, where negative pressure is created to draw air in.