Relationship Between Maximum Expiratory Flow and Degree of Lung Inflation

Abstract

There is a functional relationship between transpulmonary pressure, respiratory gas flow and degree of lung inflation. Over the upper half of the vital capacity the relationship between maximal expiratory flow and degree of inflation is effort-dependent. Over the lower half of the vital capacity this relationship is primarily determined by the physical properties of the lower airways and is termed the ⍺FV curve. A simple, acceptably accurate method of obtaining the ⍺FV curve is described, as well as data showing its reproducibility and essential independence of upper airway resistance. Preliminary data based on an empirical analysis of the curves in a group of normal, cardiac and emphysematous subjects is presented. Submitted on July 21, 1958