High-frequency ventilation: current status.

Lung injury remains an important cause of morbidity among newborns who require assisted ventilation. Studies in immature animal models of respiratory distress syndrome (RDS) have shown that positivepressure ventilation with large tidal volumes damages pulmonary capillary endothelium, alveolar and airway epithelium, and basement membranes. This mechanical damage results in leakage of fluid, protein, and blood into the airways, alveoli, and interstitial spaces, leading to inhibition of surfactant activity and further injury to the lung. Cyclic changes in lung volume appear to be more important than changes in airway pressure in causing this damage, suggesting that a ventilator strategy that avoids large changes in lung volume may reduce lung injury. Consequently, considerable interest has been generated over the past 15 years in the application of high-frequency ventilation (HFV) in newborns who have respiratory failure because this technique allows ventilation with very small tidal volumes. Although studies using HFV in animal models of RDS have shown promising results in the prevention of lung injury, results of clinical studies of this ventilatory technique in newborns are not as promising. Despite many clinical trials, controversy continues to surround the indications for HFV in newborns, whether HFV is more effective than other modes of ventilation for neonatal respiratory failure, whether HFV reduces adverse outcomes, or whether HFV is more likely to result in significant long-term complications than conventional mechanical ventilation (CMV). This article provides an overview of HFV and reviews results of studies of its use for a variety of neonatal pulmonary disorders. We address its use as a primary mode of ventilation in infants who have RDS as well as its application as rescue therapy for severe respiratory failure and air leak syndromes in both preterm and term infants.