Newborn infants with a variety of underlying causes of respiratory failure who require invasive respiratory support.
Outline the best clinical practice of high-frequency ventilation (HFV) based on an understanding of the indications, benefits, risks, and optimal implementation strategies for different modalities of HFV.
High-frequency ventilation (HFV) is a group of ventilation techniques that share in common the basic characteristics of rapid ventilator rate and very small tidal volume (VT). These techniques were developed several decades ago in an effort to minimize lung injury and to treat existing lung damage, in particular airleak. There are three types of HFV available for clinical use. Although similar in the basic principles of ventilation, each HFV modality has its own unique features. With high-frequency oscillatory ventilation (HFOV), gas within the large airways is moved in and out by pressure oscillations generated by a piston, diaphragm, or an intermittent expiratory venturi. Irrespective of how the oscillations are generated, the key feature of a true oscillator is that at 1:1 inspiratory: expiratory ratio, the negative pressure deflection is equal to the positive deflection, and therefore both the inspiration and expiration phases are active. The only HFOV currently approved for use in newborn infants in the United States is the Sensormedics 3100A (Vyaire Medical, Chicago, IL). Several more modern oscillators are available throughout the rest of the world and include the Humming V, the Flowline Dragonfly, the Stephan SHF 3000, the SLE 5000, the Leoni Plus, and the Babylog VN500. The latter is currently being evaluated in a clinical trial and may become available in the United States (the VN500 and the Leoni HFOV are already available in Canada). Unlike the Sensormedics, modern oscillators have the ability to measure, and in some cases automatically regulate, delivered VT, which should substantially reduce the risk of inadvertent hypocapnia.
High-frequency jet ventilation (HFJV) delivers short pulses of pressurized gas directly into the upper airway via a special endotracheal tube adaptor containing an HFJV injector port and a pressure monitoring port. In contrast to HFOV, exhalation is passive, resulting in somewhat lower optimal operating frequencies. The mean airway pressure is primarily generated by applying positive end-expiratory pressure via a conventional ventilator used in tandem, sometimes combined with very low rate conventional mechanical ventilation to provide periodic sigh as a means of lung volume recruitment. The inspiratory time is very short, and this characteristic appears to make HFJV uniquely suitable for treatment of airleak. The only jet ventilator available in the United States is the Bunnell LifePulse (Bunnell Inc. Salt Lake City, UT).
High-frequency flow interruption (HFFI) also known as high-frequency percussive ventilation (HFPV) generates short bursts of gas delivered directly into the ventilator circuit without the narrow injector cannula used in HFJV. For many years, the Infant Star 950 ventilator ...