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Persistence of Airway Obstruction and Hyperresponsiveness in Subjects With Asthma Remission: Respiratory Symptoms

Published in Asthma

On initial questionnaire, 29 asthmatics “in remission” (15 controls) described occasional respiratory symptoms following either allergen exposure (n=15, 6 controls), viral infections, or exposure to different conditions or stimuli (humidity, cold air, smoke, heavy exercise).
During the 14-day period of PEFR measurement and symptoms recordings, 12 “ex-asthmatics” (one control) had symptoms such as either dyspnea, cough, wheezing, or chest tightness. In four, these followed exposure to an allergen to which they were sensitized. Of these 12 subjects, 6 had a PC20 <8 mg/ ml, 2 between 8 and 20 mg/ml, 3 >20 mg/ml, and one reacted to saline solution. The control subject, whose PC20 was 54.5 mg/ml, had cough and wheezing; these symptoms were related to recent exposure to tree pollens.
Correlation Between Perception of Bronchoconstriction and Airway Responsiveness or Airflow Obstruction
During methacholine inhalation tests, dyspnea and the perception of a fall in FEVi were evaluated according to a modified Borg scale (0 to 10). Canadian health care mall More info In the 20 asthmatics “in remission” with a PC20 <128 mg/ ml, mean Borg score at 20 percent fall in FEVi was 1.63 ±0.40 for dyspnea and 1.78 ±0.30 for perception of bronchoconstriction (controls [n=19]: dyspnea: 1.05 ±0.25, perception of bronchoconstriction: 1.61 ±0.26). Dyspnea and bronchoconstriction were perceived similarly by both groups of subjects. Perception of dyspnea was significantly correlated to the level of airway responsiveness in the control group only (rs=0.546, p=0.045). There was no significant correlation between the perception of either dyspnea or bronchoconstriction and baseline FEVi.
We showed that compared with control subjects with no history of asthma, subjects who consider themselves to be in asthma remission have significantly lower FEVi, FEF25-75%, and FEVi/FVC, increased bronchodilator response, increased lung volumes, and an increased airway responsiveness to methacholine. Perception of bronchoconstriction is not reduced in these subjects but some have respiratory symptoms that may be compatible with asthma, although these are not recognized as such. This suggests persistence of asthma in most subjects who consider themselves to be “in remission,” and that studies looking at factors inducing remission of asthma should not only be based on symptoms but should also include measurements of expiratory flows and airway responsiveness.