Evaluation of airway conductance measurements in normal subjects and patients with chronic obstructive pulmonary disease.

Abstract

The relative importance of airway flow resistance in measurements of maximal air flow rates by spirometric methods and of lung volumes could not be directly assessed until the introduction by DuBois and his associates ( 1) of a specific method of measuring airway resistance. Utilizing this method, a number of investigators have compared the results of acutely induced changes in airway resistance with measurements of maximal air flow rates (2--6). In some instances (2, 3, 6), experimentally induced bronchoconstriction or bronchodilatation have resulted in appropriate changes in airway resistance without concomitant changes in maximal expiratory flow rates or timed vital capacity. In others ( 4-6), the change in airway resistance has also been manifest in one or more of the following measurements: peak flow rate (PFR), maximal breathing capacity (MBC), maximal midexpiratory flow rate (MMEF), or the one-second forced expiratory volume (FEY,). Nadel and Tierney (7) demonstrated that airway resistance decreases immediately after a deep inspiration and pointed out that this may explain why such methods as the forced expirogram, which require such an inspiratory maneuver, sometimes fail to measure changes in airway resistance. Relatively little attention has been directed to the relationship between airway resistance and maximal ventilatory rate measurements in subjects whose airways have not been subjected to experimentally induced acute changes, and only two reports have dealt with this relationship in patients with pulmonary disease