ABSTRACT
High frequency ventilation (HFV) is a generic term defining very diverse modalities of assisted ventilation having little in common except elevated frequency and reduced tidal volume. Whatever the criteria or definition, workers recognize HFV as assisted ventilation with an accelerated frequency and a tidal volume less than that which one would intuitively expect could support adequate gas exchange. High frequency positive pressure ventilation was the first kind of HFV to be described and carefully studied. Work remains to be done in the area of selecting the most responsive patients, defining optimum operating conditions, developing the most reliable delivery systems and providing maximum safety during the application of jet ventilation. Ventilation in the physiologic range combines convection and diffusion. Convection occurs in the larger airways where there is a finite net movement of air. Ventilatory assistance by the introduction of a cyclic jet of oxygen at physiological frequencies through a small cannula was introduced by Sanders in 1967 to assist bronchoscopy.
