Paradoxical breathlessness in asthma

This study tested the hypothesis that breathlessness in asthma relates linearly to airway obstruction when situational, attentional and emotional influences are held constant via random presentation of different intensities of externally applied airflow obstruction. Adolescents with stable asthma and normal controls (n=25+25) with lung functions of approximately 3.5 l forced expiratory volume in 1 s (FEV₁) breathed through a device which obstructed airflow with five stimulus intensities, analogous to a mean reduction in FEV₁ of 8–66%. A session consisted of 10 blocks, each with presentation of five stimulus intensities plus the baseline resistance of the apparatus. Breathlessness was continuously reported by moving a lever along a 10-point scale. The mean breathlessness was computed per stimulus intensity. Lung 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 controls. Breathlessness did not correlate with severity of asthma, lung function, duration of asthma, number of exacerbations over the last six months, age, sex or anxiety.

It was concluded that the meaning of airflow obstruction in patients with asthma has changed and underlies their paradoxical responses, even when situational, attentional and emotional factors are controlled.