INTERRELATIONSHIPS OF PRESSURE, FLOW, AND VOLUME DURING VARIOUS RESPIRATORY MANEUVERS IN NORMAL AND EMPHYSEMATOUS SUBJECTS

Abstract

A method of studying the simultaneous interrelationships of pressure, flow, and lung inflation is presented. Twelve normal and 14 emphysematous subjects were studied by this intergrated approach to ventilatory mechanics. Values for pressure, flow, and lung inflation during certain clinically important respiratory maneuvers are presented. Such data provide a physiologic basis for the evaluation of many tests of ventilatory function. This is particularly true for tests quantifying maximal flow during forced expiration and for the maximal breathing capacity test. Certain important physiologic phenomena which have received little attention in the past are particularly well visualized by this technique. For example, in emphysema, flow-volume plots show that maximal expiratory flow is reduced out of proportion to maximal inspiratory flow. Furthermore, the patient with severe emphysema at rest breathes near or at his maximal achievable expiratory flow levels. The effects of these factors on the ventilatory patterns of the emphysematous subject are discussed.