Dyspnoea perception during clinical remission of atopic asthma

To the Editor:

I read with interest the paper by van den Toorn et al. 1 reporting dyspnoea perception during clinical remission of atopic asthma. The authors found that there was no difference in dyspnoea perception between remission patients and asthmatics, and they suggested that physical and psychological factors may play a role in the apparent absence of symptoms.

Recently, van der Woude et al. 2 showed that there was no difference in the perception of dyspnoea or an increase in reactivity of the airways during methacholine provocation as compared to placebo during maintenance treatment with long-acting β₂-agonists at a high dose. We have previously reported that inhalation of short-acting β₂-agonists decreases dyspnoea, but increases perception of dyspnoea induced by a resistive load in asthma 3.

With respect to the difference in results, I suggest that both a local and a central effect on perception of asthma are important. The perception of asthma involves a number of higher neural centres in the central processing of sensations related to chest wall mechanics, the effort of breathing, bronchoconstriction and airway sensitivity. Therefore, future studies containing all variables related to dyspnoea may provide an answer to dyspnoea perception in asthma.