Negative and Positive Noninvasive Pressure Ventilation

Mechanical ventilation replaces or supplements the respiratory muscles’ activity. Invasive mechanical ventilation is performed using a device that bypasses the upper airways, such as the nasal/orotracheal tube or the tracheostomy tube. Noninvasive mechanical ventilation (NIV), on the other hand, uses an interface that does not bypass the upper airways, thus avoiding some of the complications associated with intubation and improving patient comfort. Noninvasive ventilation techniques can be used using positive or negative pressure ventilators. Negative pressure ventilation, most widely used during the first half of the twentieth century, had some disadvantages such as patient discomfort, difficult ventilation in subjects with variable anatomical conformations, and poor handling of the equipment. This led to a progressive replacement, after the 1970s, of negative pressure ventilators with new positive pressure ventilation systems.