ABSTRACT
A positive pressure is applied to the airway of a spontaneously breathing patient via a facial or nasal mask. The pressure is constant through all phases of the ventilatory cycle. A third type of ventilator is called the high-frequency oscillating ventilator (HFOV). HFOV employs an ‘open lung’ strategy, using high PEEP and very small tidal volumes at respiratory rates of up to 15 Hz. The mechanism of oxygenation with this type of ventilation is not fully understood, but diffusion, convection and Pendelluft are thought to play a part. The operator sets the desired tidal volume or inspiratory pressure and the number of breaths per minute. The ventilator will then deliver these breaths. The most basic mode has been developed to try to reduce the risk of barotrauma and to address the issue of different areas of the lung having different compliance in lung diseases such as ARDS.
