Heightened cough response to bronchoconstriction in cough variant asthma.
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 FEV1 (PC20) -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 PC35 -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 PC20 -FEV1 , 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 PC35 -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.
Respiratory Medicine, Kanazawa University Hospital, Ishikawa, Japan.
Noriyuki
N
Ohkura
Masaki
M
Fujimura
Yusuke
Y
Nakade
Akihito
A
Okazaki
Nobuyuki
N
Katayama
D000305:Adrenal Cortex Hormones / Q000627:therapeutic use; D058666:Adrenergic beta-2 Receptor Agonists / Q000627:therapeutic use; D000328:Adult; D000368:Aged; D001249:Asthma / Q000175:diagnosis / Q000188:drug therapy / Q000503:physiopathology*; D016084:Bronchoconstriction; D016085:Bronchoconstrictor Agents; D001993:Bronchodilator Agents / Q000627:therapeutic use; D003371:Cough / Q000188:drug therapy / Q000503:physiopathology*; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D008297:Male; D016210:Methacholine Chloride; D008875:Middle Aged; D012129:Respiratory Function Tests; D012720:Severity of Illness Index; D055815:Young Adult
D000305:Adrenal Cortex Hormones; D058666:Adrenergic beta-2 Receptor Agonists; D016085:Bronchoconstrictor Agents; D001993:Bronchodilator Agents; D016210:Methacholine Chloride