Perception of dyspnea during exercise-induced bronchoconstriction

Abstract

After strenuous physical exercise, many subjects show a significant bronchoconstriction and report dyspnea. Despite this clinical condition being a commonly encountered situation during daily life, which may be responsible for substantial disability, there is little information on the relationship between the perception of dyspnea and exercise-induced bronchoconstriction (EIB) after a standardized exercise challenge. For these reasons, we evaluated 200 consecutive outpatients (median age 13 years, ranging from 5 to 56 years) referred to our laboratory to perform an exercise test out of suspicion of EIB. On exercise challenge, perception of dyspnea was rated on a modified bipolar Borg scale immediately before each FEV₁ measurement. Sixty-nine (35%) subjects had a positive exercise challenge, defined as a decrease of at least 20% in FEV₁ from baseline. Both the onset and the decay of dyspnea preceded those of bronchoconstriction. Overall, the rating of dyspnea in the laboratory was well related with the reports of exercise-related symptoms. Sumilarly, 36 of 77 (47%) asthmatics with a history of exertional symptoms and 24 of 65 patients (40%) without a history had a positive challenge. Asthmatics reporting exertional symptoms perceived a greater magnitude of dyspnea after exercise independently from the degree of bronchoconstriction. Overall, dyspnea was significantly, but loosely correlated to the magnitude of decrease in FEV₁, being also influenced by age, gender and BMI. Conclusions: We conclude that dyspnea recorded in the laboratory after exercise test is related to exertional symptoms reported during real life, but not completely related to EIB. The rating of dyspnea is a well-suited model to study naturally occurring exercise-induced dyspnea and a useful tool to enlarge the results of an exercise challenge.