Pressure Flow Pattern and Gas Transport using Various Types of High Frequency Ventilation

Abstract

Different High Frequency Ventilation (HFV) systems have been described so far. Common to all methods are frequencies far above normal respiratory rates combined with tidal volumes in the range of the anatomic dead space of the lungs. However, the gas transport mechanisms involved are not yet quite clear and may well be of different nature for each HFV system. One way to improve our understanding are measurements on physical models of the lungs which allow comparisons between the different methods. In the first instance pressure, flow and volume conditions can be derived from such models. For a more detail describtion of the processes a visualisation of flow profiles and local velocities in the bronchial system seems to be useful. Gastransport efficiency can be determined by the partial pressure gradiance along the conductive airways in a steady state lung model. Some of the results from this experimental measurements with 4 different HFV-systems are discussed.