High-frequency ventilation. A promising new method of ventilation

It is possible to separate high-frequency ventilators into three general categories. The first is high-frequency positive-pressure ventilation (HFPPV), which employs a volume-constant ventilator with a low internal compressible volume and small tidal volumes at rates up to 100 breaths/min. A second technique is high-frequency jet ventilation (HFJV) which employs pulsation of a small jet of gas introduced into the airway via a small catheter or an extra lumen in an endotracheal tube. With HFJV, entrainment of a small amount of gas through the proximal end of the endotracheal tube also occurs. Ventilatory rates between 100 and 1000 breaths/min have been used with this technique. Last, oscillatory ventilation (HFOV) generated by a piston pump or loud speakers placed at the airway has been used at frequencies as high as 2400 breaths/min.