Questions: 1 pts In contrast to negative-pressure ventilation, positive-pressure ventilation occurs when: air is drawn into the lungs. intrathoracic pressure falls. the diaphragm contracts. air is forced into the lungs. Next Not saved Submit Quiz (ID)

The answer is the last one: air is forced into the lungs.

Explanation for each option:

1. Air is drawn into the lungs: This describes negative-pressure ventilation, where the diaphragm contracts and the thoracic cavity expands, creating a vacuum that draws air into the lungs.

2. Intrathoracic pressure falls: This is also characteristic of negative-pressure ventilation. When the diaphragm contracts, the volume of the thoracic cavity increases, leading to a decrease in intrathoracic pressure, which allows air to be drawn into the lungs.

3. The diaphragm contracts: This action is associated with negative-pressure ventilation. The contraction of the diaphragm increases the volume of the thoracic cavity, reducing pressure and allowing air to flow into the lungs.

4. Air is forced into the lungs: This describes positive-pressure ventilation, where air is pushed into the lungs by an external force, such as a mechanical ventilator, increasing the pressure in the airways and lungs.

In summary, positive-pressure ventilation involves air being actively pushed into the lungs, as opposed to being drawn in by the natural expansion of the thoracic cavity.