Chest
Original ResearchDynamic Hyperinflation During Bronchoconstriction in Asthma: Implications for Symptom Perception
Section snippets
Subjects
Subjects with mild, moderate, and severe asthma were recruited from newspaper advertisements and Kingston General Hospital (KGH) asthma and general respirology clinics. All subjects met the American Thoracic Society criteria for a diagnosis of asthma.12 Clinical stability was defined as the absence of an exacerbation necessitating an alteration in medication for 3 weeks prior to the study. Subjects were excluded if they had a medical contraindication to MCT.13 All subjects gave written informed
Subjects
One hundred sixteen subjects (39 men and 77 women; mean age, 34 ± 1 years [mean ± SEM] mild intermittent (n = 39), mild persistent (n = 7), moderate persistent (n = 42), and severe persistent (n = 28) asthma according to the Global Initiative for Asthma classification of severity27 participated in the study. Mean duration of asthma was 17.5 ± 1.1 years. There were 26 current smokers, 32 ex-smokers, and 58 life-long nonsmokers. Baseline spirometry and lung volumes are outlined in Table 2. Airway
Discussion
Substantial DH occurred in this study even when FEV1 had only declined by an average of 25% of its baseline value, likely secondary to expiratory flow limitation (EFL), which has important implications for symptom perception in asthma. Four dominant qualitative descriptors of dyspnea in asthma emerged early in MCT when dyspnea intensity was only mild (inspiratory difficulty, chest tightness, unsatisfied inspiration, and work) and were even more prevalent at maximal response when dyspnea
Acknowledgment
The authors thank Sonja McCauley, Lori Verton, Robert Hawes, and Sheryl Ross of the KGH Asthma Research Unit for assistance with data collection, Katherine Webb of the KGH Respiratory Investigation Unit for technical assistance and review of the manuscript, and Andrew Day and Yinghua Su of the KGH Clinical Research Centre for assistance with the statistical analysis.
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This work was supported by the Ontario Thoracic Society and Physicians’ Services Incorporated Foundation. Dr. O’Donnell is funded by the Ontario Ministry of Health.
The authors have no conflicts of interest to disclose.
Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/misc/reprints.shtml).