An Experimental Comparison of High Frequency Ventilation (HFPPV and HFJV) in Open Ventilator Systems

Three modes of low-compression open systems are currently being used for high frequency ventilation (HFV): (1) insufflation catheter or double-lumen tube, (2) pneumatic valve, and (3) jet injector nozzle. Using two different ventilators—a Bronchovent and a Corning fluidic model—we studied these three systems in seven anesthetized dogs and in a lung model. In two modes of HFV (high frequency positive-pressure ventilation HFPPV and high frequency jet ventilation HFJV), the dogs were ventilated to normocarbia with a frequency of 60/min and an inspiratory time of 22% of the ventilatory cycle. There were no resulting differences in variables associated with circulation and oxygen transport. There were few differences in end-inspiratory airway pressures between the two ventilators or among the three modes of ventilation. There were no differences in tidal volume. The pneumatic valve system (without air entrainment) provided the highest peak inspiratory flow. No air entrainment was associated with use of the double-lumen tube either. With the jet injector nozzle technique, air entrainment contributed 26% of the tidal volume with the Bronchovent ventilator and 58% with the Corning ventilator. These open systems cannot provide preset tidal volumes, which would be optimal for patient safety. Optimal ventilator design in HFV demands systems that can provide volume-controlled ventilation.