title: Interpretation of cough provoked by airway challenges.
abstract: OBJECTIVE
  To analyze the cough response to three airway challenges in order to clarify whether the recording of the provoked coughs would be beneficial in the management of asthma.
  
  
  METHODS
  A prospective study.
  
  
  METHODS
  University hospital.
  
  
  METHODS
  Fifteen healthy subjects, 16 steroid-naïve subjects with asthma, and 16 subjects with steroid-treated asthma.
  
  
  METHODS
  Inhalation challenges with isotonic histamine, hypertonic saline solution, and hypertonic histamine, using an ultrasonic nebulizer and 2-min tidal breathing method.
  
  
  METHODS
  Airflow parameters were measured with a spirometer, and the coughs were recorded manually.
  
  
  RESULTS
  Coughing during the isotonic histamine challenge was associated with the degree of the bronchoconstriction induced. When this was taken into account, the healthy subjects coughed as frequently as the asthmatic subjects. During the two hypertonic challenges, the asthmatic subjects coughed more frequently than did the healthy subjects when the induced bronchoconstriction had not yet developed. At that stage of the hypertonic saline solution challenge, the mean coughing frequency was 0.7 coughs per minute (95% confidence interval [CI], 0.03 to 1.3 coughs per minute) for the healthy subjects, 2.7 coughs per minute (95% CI, 0.8 to 4.5 coughs per minute) for the steroid-naïve asthmatic subjects, and 1.3 coughs per minute (95% CI, 0.6 to 1.9 coughs per minute) for the steroid-treated asthmatic subjects (p = 0.018). For the hypertonic histamine challenge, the respective values were 0.8 coughs per minute (95% CI, 0.4 to 1.2 coughs per minute), 3.6 coughs per minute (95% CI, 2.4 to 4.9 coughs per minute), and 2.1 coughs per minute (95% CI, 1.0 to 3.1 coughs per minute; p = 0.001). This cough did not correlate with airway hyperresponsiveness.
  
  
  CONCLUSIONS
  Coughing during isotonic histamine challenge seems to be a manifestation of bronchoconstriction, and recording of the coughs may not provide additional information to airflow measurements. Frequent coughing during hypertonic saline solution and hypertonic histamine challenges in the absence of bronchoconstriction is a pathologic phenomenon. Sensitivity to the cough-provoking effect of hypertonic challenges seems to be enhanced in patients with asthma but unrelated to airway hyperresponsiveness. Therefore, the recording of the provoked coughs during these challenges may add to the information obtained from airflow measurements.
authors.affiliation: Department of Respiratory Medicine, Kuopio University Hospital, Finland. heikki.koskela@kuh.fi
authors.forename: Heikki O
authors.initials: HO
authors.lastname: Koskela
authors.forename: Kirsi M
authors.initials: KM
authors.lastname: Kontra
authors.forename: Minna K
authors.initials: MK
authors.lastname: Purokivi
authors.forename: Jukka T
authors.initials: JT
authors.lastname: Randell
mesh_terms: D001249:Asthma / Q000175:diagnosis* / Q000503:physiopathology; D016535:Bronchial Hyperreactivity; D001985:Bronchial Provocation Tests; D016084:Bronchoconstriction; D003371:Cough / Q000503:physiopathology*; D005541:Forced Expiratory Volume; D006632:Histamine; D006801:Humans; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000502:physiology; D011446:Prospective Studies; D013147:Spirometry
chemical_list: D006632:Histamine