Diagnostic value of "closing volume" in comparison to "airway resistance-lung volume plot".

Abstract

Narrowing or closing of small airways is shown in healthy young subjects, young patients with a history of obstructive airway disease in an asymptomatic period at the time of study, and in older chronic bronchitic patients with bronchial obstruction. The methods used are the conventional tracer gas (Helium) bolus tech- nique for closing volume (CV) measurements, and airway resistance/lung volume plot (Raw/V). In healthy subjects and in symptom-free patients with obstructive airway disease the CV are not very different. The Raw/V plot indicates the narrowing or closing point little earlier than the He bolus technique. It was not possible to determine CV by the He bolus technique in patients with chronic obstructive airway disease, but it could be computed from the Raw/V plot.Another group of healthy male and female young subjects was exposed to the Acetyl-choline (ACh) provocation test. Before and after provocation, CV was determined by the tracer gas technique and the airway resistance Raw and intrathoracic gas volume by the plethysmographic technique. The results indicate that measurements of Raw are more sensitive than CV in detecting the bronchomotoric changes induced by ACh provocation