High-Frequency Ventilation

ABSTRACT

Currently conventional modes of controlled mechanical ventilation, such as intermittent positive pressure ventilation (IPPV) and continuous positive pressure ventilation (CPPV), with high volumes and low rates are utilized for the rhythmic inflation of the lungs. Basically the functional characteristics of these systems have not changed since Bjork and Engstrom first reviewed them in 1955 (Bjork and Engstrom 1955; Sjostrand 1983). Impairment of cardiovascular function and increasing the incidence of barotrauma with high airway pressure were problems which have needed to be solved. Thus respiratory support using high rates and low tidal volumes of ventilation was given. High-frequency ventilation(HFV) is not totally new idea, prototypes of it are found in nature in humming birds, insects and newborn babies. Moreover, HFV was reported in 1915 by Handerson who said that an adequate gas exchange could take place with a tidal volume less than the anatomical deadspace. But since the introduction of HFV in 1967, the basic concept of respiratory physiology has changed (Sjostrand and Smith 1983). HFV has received much attention in the last 20 years, resulting in a considerable accumulation of information. Many experimental and clinical studies have detailed the potential advantages of HFV but indicate that much work needs to be done to define and clarify the clinical role of these techniques and suggest that the standardized, reliable equipment with safety systems be developed. The purpose of this review is not to offer definite information for further investigation, but simply to provide background information for a better understanding of the experimental and clinical results recently achieved by many other researchers. Limited foci are as follows: 1) Definition and classification of HFV. 2) Technical developments and considerations. 3) Physiologic aspects of HFV. 4) Clinical applications. 5) Comparative studies between IPPV and HFV. 6) Problems and looking ahead.