What type of ventilators are not typically used for noninvasive ventilation?

Negative pressure ventilators are not typically used for noninvasive ventilation because their mechanism of action relies on creating a negative pressure around the chest wall, which helps to facilitate inhalation. This type of ventilator is more cumbersome and is usually employed in specific situations like polio rehabilitation or in cases of neuromuscular diseases.

In contrast, noninvasive ventilation primarily utilizes positive pressure ventilators, which offer the benefit of delivering air directly into the lungs through a mask, minimizing the risk of complications associated with invasive techniques. High-frequency oscillatory ventilators are primarily utilized in neonatal care or for patients with severe respiratory failure and are less relevant to noninvasive techniques. Volume-controlled ventilators can also provide noninvasive support, especially in settings where targeted tidal volumes are necessary. However, the unique design and operation of negative pressure devices make them less suitable for routine noninvasive ventilation practices.