Poor perception of subjective change in breathlessness- a randomized, crossover, placebo-controlled study of asthmatic subjects.

As part of a study to validate a new assessment tool (three-minute respiratory exercise test, 3MRET) , 14 asthmatic subjects [mean (95%): age, 39 (2750) yrs, FEV 1 , 63 (5768)% predicted normal; male, 42%] were randomized to receiving either nebulised 10mg bricanyl (active) or normal saline (placebo), in a crossover, double-blind study. The mean percentage (95% Cl) FEV 1 change after nebulised active and placebo agents were +23 (+8 to +38) and 0 (-6 to +5) respectively. Subjects were asked as to whether they were less breathless (score=1), more breathless (score=2) or did not sense any change or were not sure (score=3) after each nebulisation. All 14 subjects reported a score of 1 when administered active agent. Only 2 subjects correctly scored 3 when administered placebo while the rest reported a score of 1. None of the subjects reported a score of 2. When Perception of Dyspnoea (POD) index based on 3MRET 1 was used, 9 subjects correctly recorded a reduction of POD when administered active agent and 10 subjects correctly recorded an equivocal POD index (taken arbitrarily as change of <13, a figure taken from the lower bound of 95% confidence level of the mean increase). Based on these figures, the subjective sense of change in breathlessness has a sensitivity of 100% and a specificity of only 16%, while POD index has a sensitivity of 60% and a specificity of 77%. Taken together, the findings highlighted the unreliability of subjective perception in changes of breathlessness among asthmatic subjects 2 . Symptoms limiting exercise test like 3MRET that is based on maximal repetitive inspiratory efforts capable of an individual within 3 minutes 1 may have a role in improving the detection of changes in POD. The implication on POD is huge since asthma management is primarily symptom-directed. The ability to improve the awareness of breathlessness or changes in breathlessness, by patients and clinicians will represent an important milestone in the management of asthma.