The Science Journal of the American Association for Respiratory Care
BACKGROUND: Optimal asthma management requires accurate assessment of symptom severity. However, patients and their physicians are often unable to correctly estimate the degree of airway obstruction. Poor perception of airway obstruction may compromise self-management and place patients at increased risk for asthma morbidity and mortality. The aims of this study were to evaluate the relationship among indices of lung function and perception of breathlessness in asthmatic children during both bronchoconstriction and bronchodilation and to determine a clinically useful method for identifying those at risk for poor perception of airway obstruction.
Methods: The 35 patients (ages 6-16 years) in this study were diagnosed with asthma and enrolled in a larger interventional study. They were predominantly male (22M, 13F) and African- American (23 African-American, 8 Caucasian, 2 Asian). Airway constriction was induced by methacholine inhalation followed by albuterol. Patients marked a 10 cm visual analogue scale (VAS) to indicate their perceived degree of breathlessness prior to and during each stage of the methacholine challenge and 10 minutes after bronchodilation. Three methods for assessing perception of breathlessness were examined: 1) the strength of correlation (r) between perception of breathlessness and airway caliber within subjects, 2) the perception score at a 20% decrease in FEV1 (VAS20) and 3) the interval of change in perception of breathlessness following acute bronchoconstriction (dVASbc).
Results: Poor perception of bronchoconstriction was found in 51% (18/35) of the patients based on < 20% increase in VAS (dVASbc). Forty-nine percent (17/35) of the patients failed to perceive a change in breathlessness after bronchodilation based on < 20% decrease in VAS scores post-bronchodilator (dVASbd). There was no correlation between adequate perception of breathlessness and standard spirometric measures (baseline FEV1 or FEF25-75), airway reactivity (PC20), or patient report of asthma symptoms. CONCLUSION: We conclude that in this pediatric population, poor perception of asthma symptoms is a significant problem. The majority of the VAS20 scores were in the minimally symptomatic range suggesting a major barrier to appropriate asthma self- management. This study also suggests that a change in VAS scores
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