[Dyspnoea and perception of airway obstruction]

Dyspnoea, defined as the perception of difficult or laboured breathing, is ideally quantified, using a visual analogue scale or a Borg scale.

In recent years several studies have explored the correlation between dyspnoea and the degree of airway obstruction, in both healthy subjects and patients with asthma or COPD. In these studies dyspnoea was measured in baseline state, following induced broncho-constriction or during application of an external resistive load. Dyspnoea was measured using a previously validated scale or, in some studies, a simple numerical score. The lung function variables most frequently used to evaluate the degree of correlation with dyspnoea were FEV1, and PEF, although other variables were used in some studies. Despite this marked heterogeneity in the methods used, several studies strongly suggested that, in subjects with COPD, perceived subjective improvement after an inhaled bronchodilator agent correlated with improvement of inspiratory variables. In asthmatics, the major finding was that some subjects had a very poor perception of their level of airway obstruction, a potential risk factor for severe exacerbations.

Further normative studies are needed to define how healthy subjects perceive airway obstruction.

The relationship between dyspnoea and lung function in obstructive disorders has to be evaluated separately in asthmatics and in COPD patients.