High-frequency mechanical ventilation principles and practices in the era of lung-protective ventilation strategies

The term high-frequency ventilation is used to describe a heterogeneous group of ventilation modes that are characterized by high respiratory frequencies and low tidal volumes. The increasing understanding of the pathogenesis of VILI, including concepts such as volutrauma and atelectrauma, has led to a renewed interest in the role of HFV in lung-protective ventilation strategies. Inherent to many modes of HFV are low tidal volumes and small pressure swings during the respiratory cycle, which allow for higher mean airway pressures than those safely achieved with CMV. This has the potential to reduce lung injury by limiting volutrauma, whereas maintaining bigger lung volumes at end-expiration may reduce atelectrauma. Of the various forms of HFV, HFO is the only mode with an active expiration phase. This characteristic, combined with superior gas conditioning, may make HFO a promising ventilatory strategy for adults. Although a significant amount of data exists in the literature to support the application of HFO in infants and children who have acute respiratory failure, clinical data on the use of HFO in adults is only now emerging. Early studies of applying HFO in ARDS patients have demonstrated its safety and benefit in terms of oxygenation. Additionally, limited data exist on the comparison between HFO and CMV in this patient population; however, encouraging preliminary results have been reported. The optimum strategy for the application of HFV, including the timing of HFV initiation, remains unclear.