Abstract

Asthma and chronic obstructive pulmonary disease (COPD, also called chronic airflow limitation (CAL)) are the most frequent diagnoses in patients with intrathoracic airways obstruction [1]. Often these patients show a spontaneous variability in the degree of airways obstruction, which can be documented by serial lung function measurements. Large variability in the degree of airways obstruction is indicative of an increased susceptibility of the patient to environmental stimuli that cause acute airway narrowing. Knowledge of the potential severity of these episodes of acute airways obstruction is of clinical interest. Therefore, several quantitative measures of the response of the airways to bronchoconstrictors in vivo have been advocated over the past two decades. The objective of the present guidelines is to address the methodological issues of the various available techniques, and to provide up-to-date international guidelines on standardization. The present recommendations might not represent the potentially best methodologies. However, they do represent the currently validated techniques, by which interchangeable results can be obtained among laboratories. Variable airways obstruction can be mimicked in the laboratory by challenge tests with bronchoconstrictive stimuli (fig. 1) [2]. This enables one to measure the degree of the so-called «airway responsiveness» of the subject to a particular agent. Since the bronchoconstrictive response varies from one stimulus to another, one needs to specify the challenging agent. Therefore, the term «nonspecific» airway responsiveness should be abandoned. Figure 1– Dose-response curves to inhaled methacholine using the dosimeter method in 3 subjects. Airway hyperresponsiveness in asthma is characterised by a leftward shift of the curve (hypersensitivity), a steeper slope (hyperreactivity), and an increase in maximal response (excessive airway narrowing). Modified from de Pee et al. [243] with permission. Airway hyperresponsiveness refers to an exaggerated response to the bronchoconstrictor. This is reflected by an increased sensitivity to the stimulus, which …