Experimental and theoretical models of flow during forced expiration: pressure and pressure history dependence of flow rate

Flow characteristics have been studied in elastic mono- and bialveolar lung models made from tubes and balloons in series. Flow rate variation is explained on the basis of two successive limiting factors governed by the mutual interaction of tube mechanical properties and flow characteristics, i.e. wave-speed and viscous limitations induced by the tube collapse. A numerical model of flow in an elastic monoalveolar structure has been developed. It is generally admitted that a remarkable feature of forced expiration is that the flow rate is ‘effort independent’ for approximately the lower 80 per cent of vital capacity. The present results, which describe a continuous process, suggest that the flow rate depends mostly on the external pressure and pressure history. between the 15th August 1987 and the 31st August 1988, and at other periods to him at INSERM U. 296, Faculté de Médecine, 8 av Gl Sarrail, 94010 Creteil Cedex, France.