How does a positive pressure ventilator operate?

A positive pressure ventilator operates by delivering air into the lungs using pressures that exceed atmospheric pressure. This mechanism ensures that air is effectively pushed into the airways and subsequently into the lung parenchyma, accommodating patients who may not be able to breathe adequately on their own due to various medical conditions.

The principle behind this type of ventilation is to increase intra-airway pressure, which leads to an influx of air into the lungs during the ventilatory cycle. This method is particularly beneficial in situations where spontaneous breathing is insufficient, such as in cases of respiratory failure or during surgical procedures requiring general anesthesia.

In contrast, creating a vacuum or using sub-atmospheric pressures to draw air in would describe negative pressure ventilation, which is not the function of a positive pressure ventilator. Positive pressure ventilation is also not limited to noninvasive techniques; it can be applied through various invasive methods, such as endotracheal intubation, or noninvasive methods using masks. Therefore, the focus on the characteristic of pushing air into the lungs at pressures above atmospheric pressure is what makes option C the correct choice in understanding how a positive pressure ventilator works.