High frequency ventilation in neonatology: twenty years later.

that the administration of surfactants improves pulmonary compliance but, at the same time, it is a great alveolar “recruiter,” and that positive end expiratory pressure (PEEP) contributes to stabilizing the functional residual capacity by maintaining a constant lung volume. We have also learnt that, with traditional ventilation modes, the lungs stabilize after reaching an optimal lung volume, which is then maintained to a large extent by an adequate PEEP, while with HFOV continuous distension pressure plays such role. Trying to optimize lung volume entails moving along the pressure-volume loop, in that narrow area between a collapse (atelectasis) and overdistension and, once alveolar recruitment is achieved, staying in the zone of underinflation leads to a better gas exchange in association with improved respiratory stability. It is critical to keep such constant volume, and closed aspiration systems and the administration of surfactants are of great help. It is essential to take into account the concept of “silent recruitment”, a phenomenon that continues after achieving an optimal lung volume, in order to prevent overdistension and the resulting reduction in venous return and patient hemodynamic impairment. An excessive lung volume should be noticed through radiology, the movement (vibration) of the chest, the so-called “insufficient ultrasound window” (not seeing the heart), or signs indicative of a compromised venous return. Correctly adjusting parameters and adapting them according to the patient’s course are a constant challenge. Modern ventilators with flow sensors allow to synchronize and control tidal volume delivery and help to reduce lung injuries to a minimum. In addition, flow-volume loops allow to identify situations that call for special attention. However, not even the most advanced technological systems can replace a highly trained individual who is committed to providing patients with a continuum of care. The hope to find in HFOV an option capable of reducing lung injuries in very low birth weight newborn infants and, consequently, the incidence of bronchopulmonary dysplasia, was not reflected in the different studies that looked to demonstrate such benefits. Although these studies confirmed that HFOV was safe, a long time had to elapse High frequency ventilation in neonatology:twenty years later