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Heightened cough response to bronchoconstriction in cough variant asthma
Author(s) -
OHKURA NORIYUKI,
FUJIMURA MASAKI,
NAKADE YUSUKE,
OKAZAKI AKIHITO,
KATAYAMA NOBUYUKI
Publication year - 2012
Publication title -
respirology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 85
eISSN - 1440-1843
pISSN - 1323-7799
DOI - 10.1111/j.1440-1843.2012.02208.x
Subject(s) - bronchoconstriction , medicine , methacholine , asthma , anesthesia , residual volume , respiratory disease , lung volumes , lung
Background and objective: The pathophysiology of cough variant asthma (CVA) is poorly understood. We compared bronchoconstriction‐triggered cough between CVA patients and normal control (NC) subjects. Methods: There were two protocols in the study. We measured bronchial responsiveness to methacholine (MCh) and counted the number of coughs in nine CVA patients and seven NC subjects (Study A). Using partial and full flow–volume curves, expiratory flow of the partial flow–volume curve at 40% above residual volume level (PEF40) and FEV 1 were used to measure bronchoconstriction. Mild bronchoconstriction was defined as a 35% fall in PEF40 (PC 35 ‐PEF40), and more severe bronchoconstriction as a 20% fall in FEV 1 (PC 20 ‐FEV 1 ). In study B, the same measurements were obtained in six CVA patients before and after therapy. Results: In study A, more coughs were provoked at PC 35 ‐PEF40 in CVA patients (median, 60 coughs/32 min post challenge; range, 12–135) than in NC subjects (median, 0/32 min; range, 0–13; P < 0.05). At PC 20 ‐FEV 1 , more coughs were provoked in CVA patients (median, 60/32 min; range, 12–150) than in NC subjects (median, 20/32 min; range, 0–54; P < 0.05). In study B, the six CVA patients who underwent re‐examination after treatment had less coughs at PC 35 ‐PEF40 (median, 3/32 min; range, 0–14) and PC 20 ‐FEV1 (median, 13/32 min; range, 3–26) after therapy than before therapy (median, 54/32 min; range, 33–125 and 52/32 min, 45–96, respectively; P < 0.05). Conclusions: We identified heightened cough response to bronchoconstriction as a feature of CVA.