Real and pseudo late asthmatic reactions after submaximal exercise challenge in patients with bronchial asthma. A new definition for late asthmatic responses after exercise challenge

The late asthmatic reaction after exercise challenge remains a controversial issue. In this study, 21 patients recorded peak expiratory flow rate (PEFR) on two control days without performing exercise. There was no difference between both control days when PEFR at 1 h was compared with baseline PEFR and when PEFR at 4 to 13 hours was compared with baseline PEFR. After analyzing variation coefficients of baseline PEFR on a control day and exercise day, PEFR was not allowed to differ more than 15.3 percent in the same patient when comparing exercise day and control day for the late fall in PEFR in the study. In 17 of 81 patients, a late asthmatic reaction after exercise challenge was present when PEFR fall was greater than or equal to 20 percent compared with baseline PEFR value. In eight of the 17 patients, a real late asthmatic reaction to exercise challenge was present with a PEFR fall greater than or equal to 20 percent on at least three successive time points and who had a PEFR fall greater than or equal to 20 percent compared with corresponding clocktime on a control day. The late asthmatic reaction to exercise challenge is characterized not as a nonspecific epiphenomenon, but as a fall in PEFR of greater than or equal to 20 percent compared with baseline PEFR value and with corresponding clocktime on a control day on at least three successive time points. Graphic illustration of airway responses following exercises may facilitate the detection of a late asthmatic response.