Historic and future development of high-frequency ventilation.

High-frequency ventilation (HFV) has not one but several histories. Proceeding along largely independent pathways are techniques using frequencies of 1-5 Hz and techniques using 10-40 Hz, the former being introduced by Sjostrand in 1971, the latter by Lunkenheimer in 1972. It was nearly ten years before it was recognized that these techniques must radically alter our concepts of gas transport within the lung. There has also been an unfortunate series of clinical studies purporting to show that HFV is superior to conventional ventilation in patients with lung disease. There is no doubt that nearly all reports show that HFV controls PaCO2 very easily, and that the mechanisms by which this is achieved is the primary topic of the symposium. What has not been proved is that HFV is better than conventional ventilation in increasing PaO2. The mechanisms of oxygen exchange when the lung has extensive shunts are quite different from those for CO2 exchange, and this problem has not been rigorously addressed.