During high frequency oscillation ventilation (HFOV) small tidal volumes are delivered at fast frequencies, usually between 10 and 15 Hz. Meta-analysis of randomised trials of prophylactic HFOV versus conventional ventilation have demonstrated only a modest reduction in BPD amongst survivors in the HFOV groups. Similarly, no long term advantages of HFOV have been highlighted when it is used as rescue mode, but there have been few randomised studies. During liquid ventilation, the lungs are filled with perfluorocarbon, which, compared to water, has low surface tension and a high solubility for respiratory gases. Clinical experience of liquid ventilation is limited, but improvements in oxygenation and lung function have been shown in short term studies.