What is the primary function of negative pressure ventilators?

The primary function of negative pressure ventilators is to mimic the natural mechanics of respiration by creating a vacuum effect that pulls air into the lungs. This is achieved by decreasing the pressure around the thoracic cavity, similar to how the diaphragm works during normal inhalation. When the pressure outside of the lungs decreases, it allows atmospheric pressure to push air into the lungs, facilitating the inhalation process. This method is particularly useful for patients who may have compromised respiratory function, as it can help them breathe without requiring direct positive pressure applied to their airways.

In contrast, forcing air into the lungs is characteristic of positive pressure ventilation, which directly pushes air into the respiratory system, rather than creating a vacuum effect. Increasing peak inspiratory pressure (PIP) is relevant in the context of managing ventilation settings in positive pressure systems, but it does not apply to the function of negative pressure ventilators. Directly applying pressure to the airway is also a function of positive pressure ventilation, where air is mechanically delivered into the lungs through an endotracheal tube or mask. Negative pressure ventilators do not utilize this method and instead function by manipulating the pressure differential around the thoracic cavity.