Different dyspnoea perception in COPD patients with frequent and infrequent exacerbations

Background Some patients with COPD report frequent acute exacerbations (AECOPD) of the disease (FE), whereas others suffer them infrequently (IE). Because the current diagnosis of exacerbation relies on patient's perception of increased symptoms (mostly dyspnoea), we hypothesised that dyspnoea perception might be different in COPD patients with FE (>= 2 exacerbations or 1 hospitalisation due to AECOPD in the previous year) or IE (<= 1 exacerbation in the previous year), AECOPD being defined by the institution antibiotics and/or steroids treatment, or hospital admission. Objective To test the hypothesis that dyspnoea perception is increased in FE and/or decreased in IE with COPD. Methods We compared the perception of dyspnoea (Borg scale), mouth occlusion pressure 0.1 s after the onset of inspiration (P-0.1) and ventilatory response to hypercapnia (Delta V-E/Delta PETCO2) in 34 clinically stable COPD patients with FE (n= 14) or IE (n= 20), with similar age, gender, body mass index and degree of airflow limitation. As a reference, we studied a group of age- matched healthy volunteers (n= 10) with normal spirometry. Results At rest, P-0.1 was higher in FE than IE and controls (p< 0.01). Compared with controls, the ventilatory response to hypercapnia was equally blunted both in FE and IE (p< 0.001). Despite similar spirometry, during rebreathing peak Borg score and Delta Borg were higher (p< 0.01) in FE and lower (p< 0.01) in IE, than in controls. Conclusions Dyspnoea perception during CO2 rebreathing is enhanced in FE and blunted in IE. These differences may contribute to the differential rate of reported exacerbations in FE and IE.