Perception of dyspnea during exercise-induced bronchoconstriction

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 FEV 1 measurement. Sixty-nine (35%) subjects had a positive exercise challenge, defined as a decrease of at least 20% in FEV 1 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 FEV 1, 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.