Paradoxical breathlessness in asthma

This study tested the hypothesis that breathlessness in asthma relates line arly to airway obstruction when situational, attentional and emotional infl uences are held constant via random presentation of different intensities o f externally applied airflow obstruction. Adolescents with stable asthma an d normal controls (n = 25 + 25) with lung functions of approximately 3.5 1 forced expiratory volume in 1 s (FEV1) breathed through a device which obst ructed airflow with five stimulus intensities, analogous to a mean reductio n in FEV1 of 8-66%. A session consisted of 10 blocks, each with presentatio n of five stimulus intensities plus the baseline resistance of the apparatu s. Breathlessness was continuously reported by moving a lever along a 10-po int scale. The mean breathlessness was computed per stimulus intensity. Lun g function and anxiety were measured before and after the test. Participants with asthma, not controls, manifested a paradoxical response: they reported significantly more breathlessness, but undifferentially. One patient against 12 controls reported consistently more breathlessness from baseline to severe obstruction. The hypothesis was only supported for contr ols. Breathlessness did not correlate with severity of asthma, lung functio n, duration of asthma, number of exacerbations over the last six months, ag e, sex or anxiety. It was concluded that the meaning of airflow obstruction in patients with a sthma has changed and underlies their paradoxical responses, even when situ ational, attentional and emotional factors are controlled. (C) 2000 Elsevie r Science Ltd. All rights reserved.