High-frequency ventilation. A new concept in mechanical ventilation

High-frequency ventilation has been shown to provide adequate pulmonary gas exchange in patients who require mechanical ventilation. The advantage of this method of ventilation is that it may allow effective gas transport without high airway pressure or depression of hemodynamic function and thus avoid barotrauma or decreased cardiac output. Currently, three major systems have evolved. (1) High-frequency positive-pressure ventilation uses frequencies of 60 to 120/min, and gas is delivered through a pneumatic valve system. It has been successfully used during surgical procedures, laryngoscopy, and bronchoscopy. (2) High-frequency jet ventilation uses compressed gas delivered through a small-bore cannula at frequencies of up to 400/min. This technique has been used during laryngoscopy and seems to be promising for ventilation of patients with disruption of the airway. (3) High-frequency oscillation uses a wide range of frequencies, up to 40 HZ, and small quasi-sinusoidal volume excursions. It has been reported to provide adequate pulmonary gas exchange in human volunteers and patients in respiratory failure requiring mechanical ventilation. The mechanism of gas transport during high-frequency, low-tidal-volume ventilation is not well understood, but theoretic models suggest that enhanced diffusion, interregional mixing, and intra-airway velocity profiles may be important factors.