MedWire News: Stable chronic obstructive pulmonary
disease (COPD) patients with a hypersensitive cough reflex in
response to inhaled capsaicin have increased serum C-reactive
protein (CRP) levels and an increased frequency of subsequent
exacerbations, research shows.
"Hypersensitivity of the cough reflex to capsaicin inhalation
might indicate that a patient is predisposed to frequent
exacerbations, even when they have apparently stable COPD," report
Shigeo Muro (Kyoto University, Japan) and colleagues in the journal
Respirology.
The findings are compatible with observations that cough-reflex
sensitivity is associated with subjective cough, and that
subjective cough is a predictive factor for frequent exacerbations,
say researchers.
As the group points out, the causes of exacerbations in COPD
patients are poorly understood. The purpose of this study was to
examine the association between cough-reflex sensitivity in
patients with stable COPD and the frequency of subsequent
exacerbations.
The study group comprised 45 COPD patients and 10 controls. The
cough reflex was assessed in patients inhaling increasing
concentrations of capsaicin for 15 seconds during tidal breathing,
at 60-second intervals, and the log concentration causing 5 or more
coughs (C5) was recorded.
The concentration of capsaicin needed to induce cough was
significantly lower in the COPD patients than in the control
group.
Among those with COPD, hypersensitivity of the cough reflex was
significantly correlated with serum CRP levels and significantly
associated with the exacerbation frequency in the following 12
months from baseline.
The present study suggests that cough-reflex hypersensitivity is
related to increased systemic inflammation at baseline, which
increases the risk for exacerbations even among stable
patients.
The researchers note that other studies have shown COPD
exacerbations to be associated with increased airway and systemic
inflammation, and airway inflammatory markers in COPD patients are
related to the frequency of exacerbations.
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