title: Poor perception of dyspnea following methacholine challenge test in patients with asthma.
abstract: OBJECTIVE
  To determine the proportion of asthma patients with a poor perception of dyspnea, correlating the level of that perception with the severity of acute bronchoconstriction, bronchial hyperresponsiveness, use of maintenance medication, and asthma control.
  
  
  METHODS
  Uncontrolled clinical trial involving asthma patients treated at the Pulmonology Outpatient Clinic of the São Lucas Hospital, in Porto Alegre , Brazil. Methacholine challenge testing was performed using a five-breath dosimeter protocol. The perception of dyspnea after each breath was determined using the Borg scale. Data concerning asthma control, medication in use, and use of rescue short-acting bronchodilators were recorded.
  
  
  RESULTS
  Of the 65 patients included in the study, 53 completed the evaluation. Of those, 32 (60.5%) showed adequate perception of dyspnea after the methacholine challenge test, whereas 21 (39.5%) did not perceive any changes in the degree of dyspnea even after a 20% fall in FEV1. There were no significant differences between the two groups regarding baseline FEV1, percentage fall in FEV1, and the dose of methacholine causing a 20% fall in FEV1. The perception of dyspnea was not significantly associated with age (p = 0.247); gender (p = 0.329); use of maintenance medication (p = 0.152); asthma control (p = 0.562), bronchial hyperresponsiveness (p = 0.082); or severity of acute bronchoconstriction (p = 0.749).
  
  
  CONCLUSIONS
  A significant proportion of asthma patients have a poor perception of dyspnea. The factors related to the inability of these patients to identify changes in pulmonary function have not yet been well defined. In order to reduce asthma-related morbidity and mortality, it is essential that this group of patients be identified and counseled.
authors.affiliation: Pontifical Catholic University of Rio Grande do Sul – São Lucas Hospital, Porto Alegre, Brazil.
authors.forename: Cláudia Loss
authors.initials: CL
authors.lastname: Reck
authors.forename: Daniel
authors.initials: D
authors.lastname: Fiterman-Molinari
authors.forename: Sérgio Saldanha Menna
authors.initials: SS
authors.lastname: Barreto
authors.forename: Jussara
authors.initials: J
authors.lastname: Fiterman
mesh_terms: D000208:Acute Disease; D000328:Adult; D001249:Asthma / Q000175:diagnosis / Q000503:physiopathology*; D001985:Bronchial Provocation Tests; D016084:Bronchoconstriction / Q000187:drug effects*; D016085:Bronchoconstrictor Agents; D004417:Dyspnea / Q000139:chemically induced / Q000175:diagnosis / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D016210:Methacholine Chloride; D010465:Perception / Q000502:physiology*; D012720:Severity of Illness Index
chemical_list: D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride